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Vacant PhD topics at Delft University of Technology as of 2009 Those, who wish to pursue a PhD on topics other than given below, are requested to contact Mr Cees Timmers at c.timmers@tudelft.nl

1. Energy Electrical power engineering Title New Generation Wind Turbine Generators Researcher Supervision in China

Supervision in The Netherlands

Prof.dr. J.A. Ferreira

Short description Accompanied with the fast economic growth, China faces continuous growth of electric power demand. It is estimated that the electric power demand of China will increase about 260% from 2000 to 2030. Renewable energy source can help to avoid future energy crisis, limit pollution and protect the environment. The continuous economic growth of China depends on the utilization of sustainable energy source. Among all the sustainable energy sources, wind power is the most mature and economic efficient technology. China has large amount of wind power potential, which is estimated between 160GW and 250GW. According to the "Eleventh-five" national development plan made by China government, the wind energy installation capacity in China is should grow to be 5000 MW until 2010 year. TUDelft covers the full research fields of wind energy, from blade design to wind power integration. The Chinese company Goldwind has approached the TUDelft to collaborate in wind energy. This project is about the power electronic converter and electromechanical generator design of the next generation of wind turbines. The Electrical Power Processing group of TUDelft is doing research on a 10MW directly driven wind turbine, and the research project of the PhD will be part of this activity.

Title A new generation of passive components Researcher Supervision in China

Supervision in The Netherlands

Prof.dr. J.A. Ferreira

Short description China does most of the power electronics production in the world. A challenge in the design of power electronic converters is to increase the power density, or in other words, the miniaturization of the power supplies. Miniaturized power supplies use less material and have to be more efficient making it possible to build smaller and more compact electronics systems and reduce the weight of automotive and aerospace systems.

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It is difficult to introduce new passive components on the market. The profit margin is small and many manufacturers may not be willing to pay higher prices for improved components. However, passive components are now becoming the main limiting factor when it comes to improving the power density. The silicon components have been integrated in monolithic circuits and power modules consequently the passive components now dominate in number and they are occupying an increasing part of the volume of power electronic converters. We have reached a point where passive components are becoming a limiting factor for the further progress in the technology development. In this proposal we consider the filter sub-circuit (switching frequency, line frequency and EMI filters) in power electronic converters comprising a number of passive components. Using innovative approaches in which the possibilities that the underlying manufacturing technologies offer are exploited, we will identify a new generation of passive components. We see two possible approaches: - The first possibility is to retain the current discrete components modifying them as to improve their system integration with focus on “First time right” design. - The second possibility is to introduce an integrated passive component circuit where the full filter is integrated in a power module similar to and compatible with current semi-conductor power modules. The first is a smaller step where a new family of components are designed and developed based on an identified library of filter topologies that serve most industry applications. These components will interact with each other in an optimal way regarding electrical, thermal, geometrical and EMI issues and when used in the identified filter topology libraries will result in “First time right” solutions. The second possibility represents a leap where system integration is combined with physical integration. The challenge not merely lies in the hybrid integration of the components but in specifying and design a universal filter. It is a filter module that can be used in an application range that is large enough so that the production volumes can be large enough to make the product cost effective. Such a Passive Component Power Module (PCPM) should be able to filter the switched waveforms sufficiently that harmonic distortion and EMI specifications are met over a range of filter applications.

Various PhD topics in Wind Energy Please contact Mr Cees Timmers for further information

SOLAR CELLS 2-D modelling of thin-film solar cells Introduction : The Solar Cells group at Delft University of Technology has developed a 1-dimensional (1-D) device simulator ASA (Advanced Semiconductor Analysis). This simulation program is pre-eminently suitable for studying thin-film solar cells. The ASA program integrates both optical and electrical modelling and includes most advanced physical and material models for both crystalline and amorphous semiconductors. The program is used all over the world by the leading research groups in the field of thin-film solar cells. The ASA program can successfully carry out the analysis and predict the performance limits of current thin-film silicon solar cells. However, to push the efficiency of thin-film solar cells towards 20% it is required to investigate 2-D effects of light propagation and spatial variation of electric transport. The 2-D simulations can result in breakthroughs that will point out the way for experimental work to develop 2-D or 3-D structures in order to deliberately improve the light management in the solar cells and improve collection of photo-generated charge carriers.

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Description: The ASA program will be extended into 2-D device simulator. Device geometrical description and extension of the solution of a set of semiconductor equations into 2-D will be executed. Simulations of the effect of 2-D structures, such as 2-D photonic crystals, on the performance of solar cells will be carried out. Challenges: A model for light propagation from 2-D geometrical structures has to be developed and implemented into the program. The developed program modules have to be step by step tested and calibrated using 2-d experimental structures. Requirements: A student should have a good background in semiconductor device physics and modelling skills. Research project 2: Development of thin-film nano-crystalline silicon solar cells Introduction: Hydrogenated microcrystalline silicon (µc-Si:H) deposited by low-temperature PECVD technique is a promising candidate for the low band-gap material in multi-junction a-Si:H based solar cells. The University of Neuchâtel introduced a micromorph tandem solar cell in 1994, which comprised an amorphous silicon top cell and a µc-Si:H bottom cell1. The promising potential of the micromorph cell concept was soon demonstrated by the fabrication of micromorph tandem and triple solar cells with stabilized efficiencies in the range of 11 to 12%2,3 and Kaneka Corporation started the development of micromorph module production technology. The microcrystalline silicon films are a mixture of crystalline and amorphous silicon phase that varies as a function of thickness of the film. The size of crystallites is in the range of nanometers and therefore this material has been recently referred to as nano-crystalline silicon (nc-Si:H). These films are deposited from mixtures of silane and hydrogen using plasma-enhanced chemical vapor deposition (PECVD) techniques. A general feature using these deposition conditions is an inhomogeneous growth in which the fraction of amorphous and crystalline phase changes. There is a general consensus that the best nc-Si:H material for use in solar cells is at the transition from a mixed amorphous and crystalline phase to fully crystalline phase. However, the optimal nc-Si:H material regarding the fraction of crystalline part in the films has still to be identified. At the same time, the deposition conditions for a homogeneous growth of nc-Si:H films with a particular crystalline fraction have to be determined. Description: Deposition conditions of nc-Si:H films will varied and the structural and opto-electronic properties of resulting films will be characterized. Also the deposition conditions for ultra-thin doped nc-Si:H layers (20 to 30 nm thick) will be optimized. Solar cells with nc-Si:H absorber layers will be fabricated and characterized. Challenges: Determine deposition conditions for growth of uniform films regarding the crystalline fraction in the nc-Si:H films. Determine the optimal crystalline fraction in the nc-Si:H films for obtaining the highest performance of solar cells with the nc-Si:H absorber layer. Optimize the doped and buffer layers for maximal solar cell performance. Requirements: A student should have a good background in semiconductor device physics and some experience with deposition and characterization of thin semiconductor films.

1 J. Meier, S. Dubail, R. Flückiger, D. Fischer, H. Keppner, A. Shah, in Proceedings of the 1st World Conference on Photovoltaic Energy Conversion, Hawai (1994), p. 409-412. 2 J. Meier, S. Dubail, J. Cuperus, U. Kroll, R. Platz, P. Torres, J.A. Anna Selvan, P. Pernet, N. Beck, N. Pellaton Vaucher, Ch. Hof, D. Fischer, H. Keppner, A. Shah, Recent progress in micromorph solar cells, J. Non-Cryst. Solids 227-230 1250-1256 (1998). 3 K. Yamamoto, M. Yoshimi, Y. Tawada, Y. Okamoto, A. Nakajima, Thin film Si solar cell fabricated at low temperature, J. Non-Cryst. Solids 266-269 1082-1087 (2000).

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Research project 3: 2-D photonic crystals for efficient light management in thin-film silicon solar cells Introduction : For obtaining high conversion efficiency of thin-film silicon solar cells the proper light management inside the solar cell structures is of great importance. At present the light management is accomplished by light-trapping techniques that are based on the introduction of surface-textured substrates and the use of special layers called back reflectors. These light trapping techniques have been first introduced in thin-film amorphous silicon (a-Si:H) solar cells in the 1980s and resulted in an increase of short-circuit current density of 3 to 5 mA/cm2 in comparison to solar cells deposited on flat substrates and without the back reflector. The surface texture of both front glass/TCO (transparent conductive oxide) superstrates and back metal-reflector substrates has been optimized by several groups, among others the Asahi Corp. in Japan, Research Center Julich in Germany, University of Neuchatel in Switzerland, United Solar company in USA. The aim of this research project is to investigate the effect of 2-D photonic crystals fabricated in thin silicon layers on light propagation inside TF Si solar cells. Description: 2-D periodic structures can wavelength-selectively scatter and manipulate the propagation of light. A better understanding of the effects of light scattering and propagation using the 2-D photonic crystals is necessary for the development of improved light trapping schemes and implementation of these structures in solar cells. Relation between the geometrical features of 2-D structures formed in thin silicon layers and the light scattering properties will be investigated in this project. Challenges: Formation of the 2-D photonic crystals in thin silicon layers using advanced lithographic approaches. A precise measurement of the scattering parameters of 2-D structures in the wavelength range from 200 to 1200 nm. The haze parameter will be determined using an advanced spectroscopic set-up with integrated integrating ball. The angular distribution function will be determined by Angular Resolved Spectroscopy for several wavelengths. Requirements: A student should have a good background in physics and semiconductor device physics.

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FUEL CELLS Section Energy Technology, (3mE; Aravind, P.V.) Detailed modelling of flow, temperature and thermo-mechanical stress fields in a Solid Oxide Fuel Cell (SOFC) stack Background A Solid Oxide Fuel Cell (SOFC) is a device that electrochemically oxidises fuels to produce electricity. The potential produced by one fuel cell is quite small around 0.7-1.0 V, This means that to produce a useful voltage, many cells have to be connected in series to form a fuel cell stack. In SOFC stack design the gas flow distribution plays an important role. This distribution should be uniform over all cells in the stack but also inside the individual cells. Inside the cell, the anode gas flow should be distributed uniformly because of its high conversion rate. A non-uniform distribution will result in lower performance and enhanced degradation of the cell. The cathode gas flow is needed for oxygen supply and cooling. The gas flow distribution over the complete stack influences the temperature profile and hence the thermo-mechanical stress fields in the components of the stack. The Energy Technology section of the Delft University of Technology is now involved in a Dutch national initiative for designing a 20 kW SOFC stack with a specific contribution to the CFD modelling of fuel and coolant flows in the stack. This project is performed in close collaboration with the solid oxide fuel cell technology group at ECN. The proposed new PhD position is expected to augment the ongoing stack design activities at the section. The project will focus in particular on the interactions between the processes taking place in the cells (electrochemical and chemical reaction and fluid flows). Electrochemical knowledge available in the literature as well as from the ongoing studies within the section will be used for detailed CFD modelling. The Energy Technology section has two different software tools available for fuel cell modelling and they will be used for the present study (the Fluent fuel cell module and COMSOL). COMSOL also can be used for modelling thermo-mechanical stresses. The new PhD student is expected to improve the stack model which is being developed at present with specific contributions to 1) use of electrochemistry and 2) thermo-mechanical stress modelling. Objectives

1. Evaluation of the advanced electrochemical models for SOFC applications and the use of the same for CFD modelling of an SOFC stack

2. Detailed modelling of thermo-mechanical stresses in the stack. 3. To study the dynamic performance of the fuel cell stack

Proposed activities:

1. Evaluation of advanced electrochemical models for cell and stack models (literature study) 2. Improve the existing cell and stack models by including detailed electrochemistry 3. Detailed modelling of gas flow and temperature fields at cell and stack level 4. Detailed modelling of thermo mechanical stresses in the stack components 5. Propose recommendations for an improved design of the SOFC stack

Design the balance of plant components for the SOFC stack

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Energy systems with intermediate temperature solid oxide fuel cells: Fuel oxidation on ITSOFC anodes and its influence on system performance Solid oxide fuel cells are emerging as a possible choice for future energy systems. However, the fact that they have to operate at very high temperatures requires expensive materials for their construction. This increases the cost of SOFC based energy systems. By dropping the operating temperature to below 800 oC, the use of less expensive materials such as stainless steel for manifold, piping, heat exchangers, blowers, etc., can be achieved and the system is less prone to thermal degradation. However, inherently lower fuel oxidation kinetics at lower temperature may necessitate significant catalytic activity from the anodes. This in turn shall increase the influence of fuel-derived contaminants on SOFC performance. Such SOFCs, working between 600-800 oC are often called as Intermediate Temperature Solid Oxide Fuel Cells or ITSOFCs. Lower electrolyte thickness required for reducing electrolyte losses for such cells often lead to the development of anode-supported cell configurations. To evaluate the use of ITSOFCs with real life fuels, detailed understanding of the fuel oxidation on ITSOFC anodes is necessary. Knowledge of electrochemical fuel oxidation will in turn help to design and optimize the anodes for working with real life fuels and to develop macro-scale models for analyzing the performance of ITSOFC stacks. Realistic system parameters obtained from such studies also shall be used for development of thermodynamic concepts for high efficiency energy systems based on ITSOFCs such as ITSOFC- gas turbine systems. Objectives 1. To study the electrochemical fuel oxidation on intermediate temperature SOFC anodes and to

arrive at suggestions for optimal anode micro structure 2. To study the influence of various fuel gases on the performance of intermediate temperature SOFC

anodes and complete cells 3. To arrive at concepts for high efficiency ITSOFC- gas turbine systems using the information

generated from the studies mentioned above. Activities 1. Preparation of SOFC anodes with varying micro structure (TUD-ECN) 2. Impedance measurements on the anodes developed with various gas compositions and

interpretation of the results (TUD-ECN) 3. Preparation of complete cells using the developed anode (ECN). 4. Testing of the cells with varying gas compositions representing various fuel compositions (TUD-

ECN) 5. Influence of contaminants such as H2S on anode performance using impedance and I-V curve

measurements with a special focus on possible sulfur intake on ceria based anodes at reducing conditions (TUD)

6. Energy and exergy analysis of systems with ITSOFCs and gas turbines with hydrogen and natural gas with and without external reforming, resulting in a system conceptual design that enables comparison with alternative system options. Comparison of the thermodynamic performance of ITSOFC- gas turbine systems and high temperature SOFC- gas turbine systems (TUD)

The fate of NOx and N2O precursors during wet sludge fluidized bed combustion.

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In the Netherlands about 50% of the residual mechanically dewatered sludge from waste water treatment facilities is combusted using large bubbling fluidized bed combustors. The residue contains a substantial amount of fuel bound nitrogen. This leads to the formation of both NOx and N2O, the last mentioned compound being a strong greenhouse gas. NOx is reduced via ammonia injection, but there is also concern for ammonia slip at the process exhaust. TU Delft has performed an initial measurement campaign at an industrial Dutch sludge combustion facility and this has led to more insight in the fate of nitrogen species in the boiler. Now work is performed concerning the boiler modeling in order to be able to predict the emission of nitrogen oxides. The topic of the PhD study will be to further interpret the results, work on the modeling of the combustion process and perform fuel characterization in order to get better insight into the process. The aim is to develop a validated fluidized bed boiler model using which the company possibly make design modifications. The work is performed in close cooperation with the company operating the boiler. Biomass pretreatment via torrefaction using different biomass sources

The feeding of different woody and agricultural biomass types is often very challenging for thermochemical conversion processes applied to supply different energy carriers. In addition, for certain large scale conversion applications, e.g. entrained flow gasification, milling down to needed sizes of the order of 100-200 µm for high carbon conversion is not economical. Therefore, interest has grown in pre-treating biomass. One technique is torrefaction. This is a process during which biomass is heated until about 300 oC, so that the most unstable structures of the biomass, hemi-celluloses, are broken and as a consequence the material becomes more brittle. The advantage is that still a high energy content is kept in the residue, and also this residue becomes hydrophobic so that storage is improved. There are still quite some open questions concerning this process. What are the influences of heating rate on the residue properties like surface area, reactivity, composition of the released volatiles and mineral matter? The process needs to be modelled for improved understanding and up-scaling. A pilot torbed reactor is foreseen to be operated in order to obtain realistic, industrially relevant process data. NUCLEAR ENERGY Radiation Radionuclides and Reactors department; Section Physics of Nuclear Reactors (Faculty of Applied Sciences

Design of an inherently-safe Gas-cooled Fast Reactor (GFR) (1 PhD student) Dr. J.L. Kloosterman, Physics of Nuclear Reactors, Delft University of Technology To improve the sustainability of the nuclear fuel cycle, nuclear reactors are needed that can extract much more energy from thorium and uranium than is possible with present-day reactors. To this end, fast neutron reactors are needed which are able to convert U-238 to Pu-239 or Th-232 to U-233. This way, about 100 times more energy can be extracted from uranium and thorium making nuclear energy a cheap and real sustainable energy source. This PhD project focuses on the design of a Gas-cooled Fast Reactor (GFR); one of the six Generation-IV reactor designs. Due to the helium cooling, the neutron spectrum in this reactor is harder than in liquid-metal cooled reactors, facilitating a high breeding gain, but troubling the safety case of the reactor. Therefore this project focuses on the following research topics for the GFR:

• Inherently safe shut-down mechanisms to mitigate the consequences of reactivity induced accidents.

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• Inherently safe decay heat removal systems to prevent core damage after a loss-of-cooling accident.

• Sustainable fuel cycle based on the uranium-plutonium fuel cycle or on the thorium-uranium cycle.

The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. The research will be carried out in cooperation with the other main labs and universities in Europe and the USA.

Design of a small inherently-safe Nuclear Battery (1 PhD student) Dr. J.L. Kloosterman; Physics of Nuclear Reactors, Delft University of Technology At present, about 1 billion people rely on nuclear energy for their electricity needs. In Europe, 35% of all electricity and 50% of base load capacity originates from nuclear. A growing momentum towards small-sized reactors and non-electric applications indicate that nuclear energy can serve other needs as well. Small inherently-safe nuclear reactors with a long-life core, called Nuclear Batteries, can generate energy for decades at a low and constant price without refueling. Examples of applications are:

1. Electricity and heat production for industrial consumers. 2. Electricity and/or heat production for isolated communities. 3. Ship propulsion. 4. Sub sea applications to enable the exploitation of oil/gas fields far off the coast.

The PhD student will investigate the following topics:

1. Selection of optimal coolant for a Nuclear Battery. Preferably the Nuclear Battery is cooled via natural circulation of a liquid coolant at atmospheric pressure, but forced cooling options using liquids or gases can be considered as well.

2. Optimization of the burnable poison/fertile fuel distribution, and enrichment zoning of a Nuclear Battery with a thermal neutron spectrum. The initial surplus reactivity needs to be compensated by passive means. The aim of this study is to get a reactivity swing as small as possible and for a period as long as possible. Advanced techniques will be developed to calculate the sensitivity of the results to the initial conditions.

3. Research into the transient behaviour of the Nuclear Battery. The Nuclear Battery should be inherently safe under all circumstances, which requires sufficiently large and negative power feedback mechanisms, and passively safe decay heat removal path ways. The research into these options requires new tools to simulate the dynamic behaviour of Nuclear Batteries. The results will be applied to a Nuclear Battery preferably cooled via natural circulation of the coolant.

The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. The research will be carried out in cooperation with the other main labs and universities in Europe and the USA.

Computational neutron transport (1 PhD student) Dr. D. Lathouwers, Physics of Nuclear Reactors, Delft University of Technology Introduction With the increased focus on 4th generation nuclear systems the need for more accurate and more generally applicable predictive tools has grown. This is true also in the field of neutronics where the diffusion approximation is no longer considered adequate, e.g. due to the presence of plenums in

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pebble bed HTR’s. Generally speaking, there is a need for accurate neutron transport methods that are both applicable in all regions of physics (vacuum regions to thick diffusive media) and applicable to all geometric situations. A new method for neutron transport is based on the First Order System Least Squares method (FOSLS). It can be applied to all regions of interest, i.e. from vacuum regions to diffusive media. The method can be combined with spherical harmonics polynomials in angle and spatial finite elements to give a generally applicable method without being plagued by ray effects. This research focuses on the further development of the FOSLS method with an emphasis on solution efficiency. Project description The discretization of the neutron transport equation leads to very large linear algebraic systems. The efficient solution of these linear systems is crucial but complicated because the system is too large to be stored and because the mesh is unstructured. This project focuses on developing fast methods for the efficient solution of FOSLS-based discretizations. The PhD student will concentrate on

− Development and optimization of efficient (parallel) preconditioners to be used in (parallel)

Krylov methods. − Coupling of the FOSLS discretization to a multigrid scheme to be developed during this

project. − Compare the above mentioned options and investigate when each of them is favourable over

the other. − Investigate different time-stepping schemes and their implication on the above comparison.

The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. The research will be carried out in cooperation with other universities in Europe.

Hot spot prediction in HTR systems (1 PhD student): Dr. D. Lathouwers, Physics of Nuclear Reactors, Delft University of Technology Although the physics describing the flow in modern (Gen-IV) reactor systems is well known, its application is hampered by computational limitations. Therefore, for practical situations, approximate models are used for flow prediction and heat transfer analyses. In pebble bed reactors, where the reactor core consists of fuel pebbles, the flow is usually described approximately by considering the bed as a porous medium with its properties determined by such parameters as the pebble size. By using such an ‘average’ model one misses out on some of the features of the system. For example, hot spots could arise by a locally varying pebble packing. This PhD project focuses on the accurate prediction of such local phenomena related to heat transfer and fluid flow by coupling average or large scaled models with more detailed, smaller scale, model (hence the word hierarchical) for local phenomena. Ideally, such a hierarchical approach could be repeated on several levels. This approach has the advantage that the ‘average’ model points at regions of interest while selected regions may be investigated further with more detailed models. The cost of such an exercise would however be limited when compared to a detailed physical calculation of the complete region. The present study will concentrate on the following topics

− Choice of a reactor system as a base case for investigation (such as the pebble bed HTR) and defining the various levels (two or more) and appropriate physics models at these levels.

− Researching analogous situations of multilevel physics descriptions (e.g. nodal methods in neutron transport) and multilevel solution methods (e.g. multigrid).

− Investigation of the coupling of the levels and the required boundary conditions.

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− Application to hot-spot prediction in pebble bed HTR system. The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. The research will be carried out in cooperation with other universities in the USA.

Experimental and numerical investigation of SCWR stability (1 PhD student) Dr. M. Rohde, Physics of Nuclear Reactors, Delft University of Technology Introduction One of the promising reactor concepts selected by the Gen-IV international forum is the so-called supercritical water reactor (SCWR), in which supercritical water (p = 25 MPa, T = 280 – 500 oC) is pumped through the reactor core. The SCWR concept is now under great attention to scientists and is subject to a number of research projects. One of the issues that need to be investigated is the system stability of the reactor. Like boiling water reactors, SCWRs are susceptible to instabilities caused by the large density differences present throughout the reactor. Small perturbations will grow weak in a stable reactor, but will increase to very large oscillations in unstable ones. The stability of the reactor depends upon the complex interaction between many physical phenomena such as the density-reactivity feedback, the drastic change of fluid properties and flow and heat transfer characteristics. Nowadays, the knowledge regarding this complex interaction is rather scarce and immature. A fundamental investigation in this field is therefore of great importance. Tasks description The PhD student will perform both a theoretical and experimental study in order to understand the physical background of the dynamics of such a system. Among other things, the student will

− perform experiments for a large range parameters (flow, power, friction, …) − perform a linear stability analysis with the help a simplified numerical model − compare experiments and numerical findings, resulting in a fundamental description of the

physics governing the SCWR stability − perform a non-linear stability analysis, thereby using the experiments as well as numerical

results

The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. For this research project, a close cooperation exists with different European universities and research institutes.

Experimental and numerical investigation of two-phase cross-flow (1 PhD student) Dr. M. Rohde, Physics of Nuclear Reactors, Delft University of Technology Introduction In Boiling Water Reactors (BWRs), the transport of the steam-water mixture significantly influences the local mixture densities and thus the local production of heat through the moderation of neutrons in the core section. On top of this, the heat transfer from the surface of the nuclear fuel to the water and

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the stability of the reactor as a whole are influenced by the transport of the steam-water mixture. One of these two-phase flow phenomena, being the transport of steam bubbles between sub-channels of the reactor core, is still not very well understood. Since the transport of bubbles highly depends on the flow structure within the gap between two sub-channels, Lexmond et al. and Mahmood et al. investigated the flow and mass transfer for one-phase flow in different geometries. Among other things, they found a regular but highly dynamical pattern of vortices that induces mass transport from one channel to the other channel. The aim of this project is to gain more understanding into the mechanism of two-phase transport between the sub-channels. Tasks description The PhD student will perform both a theoretical and experimental study in order to understand the physical background of two-phase cross-flow. Among other things, the student will

− perform experiments (PIV, LDA) in different geometries for different flows, void fractions and, thus, different flow regimes

− perform numerical calculations in order to study planes and quantities that cannot be determined by experiments

− develop understanding of the influence of the gaseous (vapor) phase on the presence of regular, dynamical flow structures (and vice versa)

− develop a model for the net transport of gas/vapor based on macroscopic parameters such as the flow and cross-sectional averaged void fraction

The research will be carried at the section Physics of Nuclear Reactors (PNR) of the faculty of Applied Physics of TU-Delft, which is well-known for its research on innovative nuclear reactor designs. For this research project, close cooperation exists with the Multi Scale Physics department of the same university.

2. Materials science and engineering Deformation of thin films of NiTi shape memory alloy NiTi (Nickel Titanium) is a shape memory alloy known for its application in satellite hinges, dental fixtures, and spectacle frames. Only recently NiTi has been prepared as a thin film. In the present project the suitability of NiTi as metallization for flexible electronics will be investigated. For this application the deformation of NiTi films is of crucial importance. Next to the shape memory effect NiTi exhibits pseudo-elasticity. This pseudo-elasticity allows bulk NiTi to be strained reversibly up to 6%. Other work on metallization for flexible electronics has demonstrated a huge thickness dependence of the maximum plastic strain to failure for gold films. Thin gold films can be stretched far more than thick films. The idea for the present project is that the pseudo-elasticity of bulk NiTi will make this material outperform simple metals in this application. In the present project NiTi thin films will be manufactured by sputter deposition and subsequent heat treatment. This procedure allows control of the grain size between 10 and 60 µm. After deposition and annealing the films will be transferred to a flexible support and subjected to tensile testing. Small single-crystal samples will be cut from the film by Focused Ion Beam milling in order to study the deformation dependence on crystal orientation. Deposition and testing will be done at TU Delft. Transfer of the films to a flexible substrate will be done at Philips Eindhoven.

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3. Civil Engineering Subject Self-healing of Concrete Structure by Using Smart Light

Weight Aggregate Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description Due to the brittleness of concrete, cracking is unavoidable in concrete

structures. Cracks facilitate the ingress of water, oxygen, chlorides, carbon dioxide, sulphates or alkalis into concrete and hence cause reinforcement corrosion and concrete deterioration. Researchers have known that cracked concrete has a potential to heal itself, since self-healing was first directly observed in cracked water pipes in 1937. A common agreement exists, that hydration of residual cement particles is one of the main causes of the self-healing of cementitious materials. In fact, quite often a consistent percentage of cement remains unhydrated over time because of the lack of water, especially in high performance concrete. If concrete cracks and water penetrates into concrete, unhydrated cement reacts with it, producing new hydration products. This growth of hydration products will eventually fill the cracks. Self-healing through hydration of residual cement particles only takes place in the presence of water. However, most concrete structures are exposed to a relatively dry environment. Moreover, even in a wet environment water may not be able to reach some internal cracks deep inside the concrete. Therefore, supplementing water at the locations where crack are formed is crucial for promoting self-healing. Recently, micro- and nano-fibres filled with water have been proposed as a water reservoir. During concrete cracking, these fibres may be broken and consequently may release water. However, these fibres may be instead be pulled out of the matrix when a crack propagates, without releasing the water. Besides, the addition of fibres has generally a negative effect on the workability of fresh concrete. For all these reasons, this project proposes to introduce into concrete a “smart” lightweight aggregate as a water reservoir. The main goal of this research is to propose, test and optimize a novel method to provide sufficient water for the further hydration of unhydrated cement particles. As mentioned, in practice it is not always easy for unhydrated cement particles to have access to water, especially when remove from the exposed surface of a concrete structure, such as at the bottom of a deck or beam. To overcome this problem, a “smart” light weight aggregate can be used. The result of this project will be the proof-of-concept of the pre-emptive self-healing concept for cracking concrete by invention the smart light weight aggregate.

Subject Design of High Ductile Concrete by Using Nano-fibers Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description The brittleness of cementitious materials, like concrete, depends on the

brittleness of the matrix, i.e. the cement paste, and on the fracture properties of the matrix-aggregate interfacial zone (ITZ). The

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interfacial transition between the cement paste and aggregates in concrete has long been considered a zone of weakness, both in terms of strength and in terms of permeation of fluids. For improving the ductility of concrete both the strain capacity of the cement paste and of the ITZ need to be modified. In this project, the modification of cement paste and the properties of ITZ will be investigated by studying the selection and dosage of additives, particle packing together with nano-fibers, in aims to improve the ductility of concrete. The chemical components and the microstructure properties of ITZ, including porosity, interconnectivity of porosity, and the nano-fibers will be performed. The final goal of this project is to delivery a design methodology for producing ductile concrete.

Subject Corrosion and Protection in Reinforced Concrete Containing

Blended Cements and/or Waste Products Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. D.A.Koleva, Dr. msc Ye Guang,

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology

Short description Corrosion of steel re-bars is one of the main causes for reinforced structures deterioration. Various methods and techniques are available and applied in practice for corrosion prevention and/or protection. In order to minimize repair and maintenance costs, and thus to significantly improve the service life of a reinforced concrete structure in an aggressive environment, preventive measures can be taken and successfully applied. One of the possibilities is Cathodic Prevention, applied either within the construction of a structure or at a later stage before corrosion initiation. This research project will combine the following main aspects:

- investigating chloride-induced corrosion initiation in reinforced concrete, containing blended cements (e.g. BFS, fly ash, etc.) and/or waste products (“red mud” as partial replacement of the cement fraction);

- application and monitoring of Cathodic Prevention for reinforced concrete, containing blended cements in comparison to OPC CEM I with two starting points (immediately after concrete casting and after 28 days).

The main research interests here are related to materials’ behaviour and to the practical application of the technique. Thus, the research will focus on: determining if the achieved steel polarization (i.e. steel protection) is sufficient, using lower then normally applied current densities (in the range of 0.5 to 1 mA/m2); studying the influence of electrical current flow on the concrete bulk microstructure at early hydration rate. The final outcome will be the establishment of a cost-effective and “materials’ friendly” corrosion prevention technique, which has all potential for direct practical application.

Subject Hydration Chemistry and Microstructure of Blended Cement System Researcher To be decided Contact DUT Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description There is now a range of additives (i.e. blast furnace slag, fly ash)

commonly used to enhance the properties of concretes and, in some cases, result in reduced materials costs. The suitability of such

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materials depends on their reactivity, their cost and their influence on the properties of the resulting concrete. All influence the internal chemistry of the cement system, i.e. pH, mineral balances, and their generally slower reaction leads to a longer equilibration time as reaction products of the additive re-equilibrate with cement hydration products. Many researches have shown that the durability of cement pastes is strongly influenced by internal chemistry and paste microstructure. Continuous or interconnected porosity often links the interior of the paste to the outside world so that aggressive chemical species can penetrate and degrade the paste internally having consequences for paste durability. The effect of the blending agents identified above on microstructure is to cause a reduction in the degree of interconnected porosity. Through numerical modeling and experimental testing the objective of this particular project will focus on the hydration chemistry of blended cement system and their consequence on the microstructure features. With the help of computer technology, the proposed theoretical model should be able to predict cement paste properties and the development of paste microstructures taken into account the type of blending agents, the compositions and the curing condition. The simulation results should be validated against experiments.

Subject Concrete Design by Multi-scale Modelling. Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description In recent years, the performance requirements of concrete structures are

continuously challenged. The increasingly stringent performance criteria have stimulated fundamental research in concrete technology and structural engineering and have meanwhile brought this on a higher level. It has led to the development of advanced software for the design of concrete structures. Meanwhile the durability of concrete structures is becoming a very issue to ensure the service life constructions. Design for 100 years service life buildings is put in front of structural design engineer. This requires the ability to model and through modeling to predict the behaviour of lasting processes over time. The predictions will be more accurate once real processes on nano- and micro-scale can be captured in the structural modeling. This can only be done by using multi-scale modeling. With the help of present multi-scale models of cementitious materials, this research aims to develop a computer based model in order to design concrete with desired properties.

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Subject The Fire Behaviour of HPC and SCC Containing Fly Ash as Filler at

Elevated Temperature Researcher To be decided Contact DUT Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description Due to the high strength, high workability and high durability, High

Performance Concrete (HPC) is widely used in various buildings and structures, such as bridges, highways, tunnels and high-rise buildings. Self-Compacting Concrete (SCC) is considered as a new generation of HPC with the advantage of no vibration during construction. Meanwhile, fillers, like fly ash, limestone powder or silicate fume are normally added in the HPC or SCC mixtures in order to obtain good workability or reduce the cost of construction. Unfortunately, even with significant advances in science and technology, risks to buildings and structures due to fire are increasing rather than decreasing. In the past, researches have shown that SCC made with limestone powder as filler have same fire risk as HPC. However, the performance of SCC made with fly ash as filler is not clear. This research focuses on the investigation of fire behaviour (chemical-physical reaction) of HPC/SCC containing fly ash as filler at elevated. Through experiments and modeling, this project will answer the question on: i) how does the water vapour pressure built up inside concrete when fly ash is used. ii) what is the mechanism behind when moisture escape from inside of concrete at elevated temperature. Finally, the criterion for preventing fire spalling of HPC/SCC containing fly ash as filler has to be proposed.

Subject Modeling of Compressive Strength of Cement Paste Based on

Effective Contact Area of Hydrating Cement Particles Researcher To be decided Contact DUT Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Microlab, Faculty

of Civil Engineering and Geosciences, Delft University of Technology Short description The gradual evolution of the materials properties of cement-based

materials is the result of the continuous change of the microstructure with progress of the hydration process. Especially, the connectivity between solid phases is essential on the mechanical properties, for example, the compressive strength and elastic moduli of cementitious materials. From the engineering point of view, the compressive strength of a cementitious material is the capacity of cementitious material to withstand axially directed forces. When the limit of compressive strength is reached, the material is crushed. It is clear that the capacity of a cementitious material is a function of the degree of cement hydration. From material science point of view, the development of compressive strength of a hardening cementitious material can be regarded as the result of the microstructural evolution due to cement hydration. This research is trying to build up a theoretical numerical computer-based model for predicting the compressive strength of cement paste. Experimental results of mechanical properties are used to calibrate the model.

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Subject Experimental study and numerical simulation of the influence of

cement type on the autogenous shrinkage of cement paste Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. msc Ye Guang, Dr E. Schlangen

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology

Short description Autogenous shrinkage is a mechanism that can cause damage in concrete structures already before the structure has been used. Of course we would like to prevent this and therefore we would like to study the mechanism in detail. In the Microlab a device has been developed to measure autogenous shrinkage of cement paste. With this machine it is possible to study the influence of cement type (fineness and composition) and the water cement ratio on the autogenous shrinkage. If it is known for cement paste the behaviour of the concrete can be predicted. The aim of the project is to find a relation between cement composition, cement fineness and water cement ratio and the amount of autogenous shrinkage of cement paste experimentally and numerically. In order to do so, in this project a device that is available in the Microlab will be used. In the meantime a literature study has to be performed on the subject. Then various mixes have to be tested and the role of composition and fineness of cement and the water-cement ratio on the autogenous shrinkage has to be investigated. A numerical model in order to predict autogenous shrinkage of concrete will be delivered.

Subject Designing and applications of Fibre Concrete Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. Ye Guang, Dr E. Schlangen

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology

Short description Fibre Reinforced Concrete is already known for decades. It has a higher fracture energy and it results in smaller distributed cracks. Since a few years UHPFRC (Ultra high performance fibre reinforced concrete) is on the market. This material has a high tensile strength and very high ductility. The material is expensive but in structures where a very high strain capacity is needed the material could be very competitive. The reason is that no reinforcement steel is needed anymore. Different types of such materials are proposed in literature, with all their own properties. But the question is, which material should be used in which application? The aim of the project is to use finite element modelling to compare various types of UHPRFC. With the help of modelling various useful applications of these materials have to be worked out. Meanwhile, using lattice model to optimize a material structure in such a way that the ductility of concrete increases. Finally, this material has to be making in the lab and to test the properties. The project will start with getting acquainted with the software tool. Next step is to study the materials behaviour of the different concretes and the models to simulate this behaviour. Then an inventory has to be made of different structures where a material with high strain capacity could be beneficial. For these applications simulations have to be performed to show what the new materials can do.

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Subject Inverse modelling of chloride ingress in cracked concrete to obtain

crack-width and crack-length Researcher To be decided Contact TU Delft Professor dr. ir K. van Breugel, Dr. Ye Guang, Dr E. Schlangen

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology

Short description Chloride ingress in concrete is of major concern, because chlorides induce corrosion of the reinforcement and with that effects the durability of concrete structures directly. Chloride ingress in cracked concrete goes even faster. The outcome of this project should be a relation between crack width (and length) and the chloride diffusion coefficient. In the specimens that are used it is, however, very difficult to measure the exact crack width and crack length. In this project it is intended to develop a procedure to fit back the dimensions of the crack from the measured chloride profiles by inverse modelling. For this existing diffusion and permeability models can be used. The aim of the project is to develop an inverse modelling procedure to obtain crack dimensions from measured chloride profiles. The project should start with a literature study on the subject. Next step is to investigate the existing test data that are available and to set up a model to simulate the chloride profiles in cracked concrete. The model should be able to reproduce crack dimensions in order to find a relation between chloride ingress in a crack and the length and width of the crack.

4. Integrated Water Resources Engineering (including energy and environmental issues)

City along the river

With the current increase of the discharge in the rivers and the rise of the sea level the current flood defences have to be improved. The floods of 1993 and 1995 have jolt the government awake and gave them the awareness that the current situation must be changed. However the current landscape completion makes it impossible to adjust the traditional dikes and alternative solutions are needed. Improving the flood defence is no longer only a water management and hydraulic problem, but it has also become a problem of spatial completion and design. Within this theme this dilemma will be investigated. Prof.drs.ir. J.K. Vrijling, ir. K.G. Bezuyen, ir. W. Molenaar, ir. B. Stalenberg

Multiple spatial use: city along the Meuse

Since human mankind settlements were founded along rivers due to strategic point of view. This occurred also along the Meuse. The settlements were founded in gravel valley, such as Maastricht, or on high grounds such as sand ridges more downstream. These settlements have grown into big cities where a large part is founded on lower grounds and where the city has moved towards the river. The city fronts of several cities along the Meuse cause bottle necks in the flow profile of the river. Due to the rising water levels flood problems will occur. A simple heightening of the flood defence is not possible. This will give the challenge to generate innovative solutions for the typical landscape in the Meuse valley. Insight is necessary of the flow area of the Meuse and its cities. The emphasis lies in the design

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of the urban adjustment in such a way that the safety is not decreased. The application of multi spatial use must not be excluded. Prof.drs.ir. J.K. Vrijling, ir. K.G. Bezuyen, ir. W. Molenaar, ir. B. Stalenberg

The floating city

The Water Management Commission 21ste century has pointed out that the society has to change their opinion about the water issue. We should not defend against water, but live with it! That is their motto. One wishes a water system with no fighting against water but embracing it. The natural system will be followed and water will be seen as an ally by filling the spatial use. Living on water and along water is an important part of this philosophy. Several concepts have been developed, which need further technical elaboration. One of these concepts is the floating city. Prof.drs.ir. J.K. Vrijling, ir. K.G. Bezuyen, ir. W. Molenaar, ir. B. Stalenberg

The floating port

Research is done on the feasibility of a floating commercial port at some distance from the mainland. An important aspect of the port as a whole is flexibility, the configuration should be relatively easily adaptable to the ever changing demands of the port authorities. Besides that, the whole complex is literally in motion, perhaps even permanently, due to wave and current forces. Underneath a (incomplete) list of subjects that should be addressed creatively in order to be able to realize a floating port:

Modular construction of a floating port terminal Modular construction of a floating breakwater Modular construction of a (floating) hinterland connection The construction and the transport of elements of the floating port The fixed points of the floating port - Stiff variant The fixed points of the floating port - Flexible variant The hinterland connection of the floating port - Floating variant The hinterland connection of the floating port - Bridge or jetty variant

Think of alternatives or come up with (an) innovative construction(s) and work these out in more detail in the framework of the floating port. Assuming the presence of a floating port there inevitably are some effects or questions that need looking into, or answering in relation to the structures designed:

What is the optimal size and shape of a floating port, what type of loads and what type of

vessels can be handled? What is, in the light of the logistic chain as a whole, the best 'system' to transfer cargo between

the mainland and the floating port? What are the morphological effects of large floating bodies? What is the environmental impact, conduct an MER or EIA. What are the necessary mitigating measures and demands that are required specifically for a

large floating structure? Are multiple functional uses of the floating elements possible? What are the costs of the construction, maintenance and possible future adaptations compared

to the traditional port expansions? Depending on the chosen subject or the question to be answered, one will cooperate with other groups both within and outside of the Hydraulic Engineering department.

Prof.drs.ir. J.K. Vrijling, ir. W.F. Molenaar

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Analysis of flood damage to buildings

An important cause of damage and loss of life due to floods is the collapse of buildings. In this research, a method is developed for the analysis of damage to buildings due to floods. Firstly, load factors that can lead to damage are investigated, e.g. flow velocity, water depth, waves and debris impacts. Consequently, the strength of buildings and failure mechanisms can be identified. The aim is to develop a generic method that can be used for different flood types (flash flood, tsunami, polder flood) and building types. Available information from damage to buildings during historical floods has to be collected. Possibly, scale model test will have to be executed. This research is executed in cooperation with Canadian partners (University of British Columbia - Vancouver). Possibly, part of the study can be done in Canada, some funding is available. This project is especially suitable for a student in hydraulic engineering constructions (constructieve waterbouwkunde) program. The project could also be suitable for two students (one hydraulic engineering and one building / structural engineering). Prof. J.K. Vrijling,ir. Bas Jonkman

Review of technical and financial aspects of PAC's

The increasing price of conventional energy production and the growing amount of alternative (wind) energy production gives new arguments to create a so called "Pomp Accumulatie Centrale or PAC" (i.e. a pumped storage plant), because such a PAC can buffer the energy between market demands and supply (nowadays at a European scale).

In the late 80-ties there were already feasybility studies undertaken (like Plan Lievense), but although they give positive results, they have never been built, maybe because of the risk that the dike-ring may collapse and give a kind of mini tsunami at the Dutch coast.

But this disadvantage has already been solved by the so called inverse "Valmeer" or bath tube solution, where instead of a high waterlevel and dikes, the level inside the dike-ring is lowered for about 40 meters. Maybe a combi-solution of new and old is also possible.

Now there is a new challenge for students, first to optimize the technical solutions and second to check the feasibility with the present prices for energy generation and storage.

ir. A. van der Toorn, ir. J. van Duivendijk

Design of deep-freeze quaywall

The trend in ports is to build more flexible in relation to changes in the lay-out ,ships e.o.. A deep-freeze quay wall could be a solution to increase the flexiblity in the ports. The aim of this masterthesis is to develop different designs in relation to the use of the quay wall including an economic comparison of the developed design alternatives.

Prof.drs.ir. J.K. Vrijling & ir. J.G. de Gijt

Horizontally installed slurry wall

Nowadays slurrywalls are installed vertically in sections, thus introducing connection troubles from panel to panel. These connections may pose problems in regard to soiltightness. A possible alternative as a construction method could be a continuously made slurrywall constructed horizontally. The aim

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of this thesis to investigate the feasibility of this type of construction and make a costs comparison with the existing vertical panel method.

Prof.drs.ir. J.K. Vrijling & ir. J.G. de Gijt

Comparative investigation of several design recommendations for quaywalls with limited and high retaining height

Several design recommendations are availalble today like EAU, CUR166, Handbook Quaywalls etc.. The aim of thesis is to inventarise the available design recommendations world wide. First an inventarisation has to be made followed by comparative computations for a quaywall with a limited- and one with a high retaining height. After evaluation of the results of these computations recommendations have to be presented for harmonising the designrules also in relation to Eurocodes.

Prof.drs.ir. J.K. Vrijling & ir. J.G. de Gijt

Design of wooden quaywall

These days most of the quyawalls are constructed of steel and concrete or a combination of these materials. The aim of this investigation is to design a wooden quaywall and make a comparison with existing sctructures of concrete and steel. Within this study the enviromental aspects have to be taken into due account. An economic evaluation is part of this study as well.

Prof.drs.ir. J.K. Vrijling & ir. J.G. de Gijt

The traditional rolling gate, which can be found in many maritime locks, requires a lot of space bides the lock (chamber). By giving it a curvature it is possible to move it away in a more sideway direction reducing the space required up to only 40% of the straight gate. To this date this type of gate has not been used in the Netherlands. A first possibility would be the new lock in IJmuiden. An interesting feasibility study in cooperation with Bouwdienst Rijkswaterstaat (Ministry of Public Works).

Prof.drs.ir. J.K. Vrijling, ir. W.F. Molenaar, ir. A van der Toorn, ir. S. de Koning (BD-RWS)

Shiplift using a tumbling chamber

For recreational craft (pleziervaart), i.e. voor smaller locks, the combination of shiplift and the old tradional portage (overtoom), resulting in the tumbling chamber, seems interesting. Elaboration of this inventive idea into a structural design and proving its feasibility is a challenging Master thesis subject. Prof.drs.ir. J.K. Vrijling, ir. W.F. Molenaar, ir. A. van der Toorn

Durability of concrete and reinforcement in breakwater caissons

Caissons are designed for serviceability and ultimate limit state conditions. For the serviceability limit state (SLS) a careful check on crack width, more specific on crack initiation and (further) development, is required. Cracked concrete will suffer from corrosion because salt water can reach the reinforcement. When the corrosion process has started it is a matter of time for reinforcement and/or structural failure. Possibly SLS will be governing and not ultimate limit state (ULS). Questions to be answered:

• How fast does corrosion develop after cracking of the concrete; • What would be the best design criterion from durability and risk point of view; • Would it be feasible to prestress breakwater caissons.

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Prof.drs.ir. J.K. Vrijling, ir. W.F. Molenaar, ir. A. van der Toorn

The Observational method as a means to cost and risk reduction.

In the Netherlands it is customary to finalize the design all parts up to any details before any construction takes place. This leads to the situation that any information such as measuring data on deformation, forces, bending moments etc that is gathered during construction does not contribute to improvement of the design or reducing the risk; this can be regarded as a waste. E.g. for a deep excavation for a building pit (Metro stations, North-Southline), de displacement of the retaining wall or the measured strut forces might give information that might lead to additional struts or on the contrary reducing the number of strut levels, than assumed in design; saving on cost or reducing the risk. This concept can be used in general e.g. the number of piles under the settlement free plate for the HSL, long Quay walls, Piers, etc. Isn't it time to use the Observational method in the Netherlands ? Prof.drs.ir. J.K. Vrijling, ir. R.B.Jongejan, dr. ir. K.J. Bakker

Settlement related to soil retaining walls

The common used relations to predict settlements related to soil retaining walls are derived by Prof Peck and published in 1969. Since then a number of new methods have been developed for the design of Soil Retaining walls. The subgrade reaction models among these did not have the option to predict surface settlements, whereas the first Finite Element models that enabled to predict the settlements, predicted a too wide and too shallow settlement profile due to the insufficiencies of the simple Mohr-Coulomb model. However since than material modelling has flourished and the newer constitutive models, such as the Hardening Soil model, including small strain analysis give much better predictions. In the proposed study one might do research on 1) the applicability of the empirical Peck relation for Dutch soil profiles; including an evaluation and analysis of measured data. 2) The role of arching on wall friction in the process, and 3) an evaluation of the best constitutive model(s) to be used for this type of analysis. 4) A case study on how to predict the settlements, discounting for the effect on existing buildings nearby. Prof.drs.ir. J.K. Vrijling, Dr.Ir K.J. Bakker In g. H.J. Everts

Axial and lateral behaviour of tubular-pile structures

It is observed from engineering practice that in design of tubular piled structures, e.g. for guiding structures, scale effects might play a role. For the smaller diameter piles it is common to design these for ultimate limit state criteria, whereas, due to the longer elastic behaviour that is observed for the larger diameters, it is realized that for these Serviceability limit state criteria have to be used in order to limit the deformation in practice; so for these the final strain at failure will never occur. It is realized that this ought to have its influence in the process to derive an optimum design. Other effects that need to be considered are buckling of the tube and eventually propping of the soil core. These effects might be researched using 2D axi symmetric or 3D Finite Element analysis. Prof.drs.ir. J.K. Vrijling, Dr. ir. K.J. Bakker Horizontal loading on Quay walls An important part of the loading of a caisson breakwater, or a caisson quay wall is the horizontal loading due to the back fill behind the caisson. For a preliminary design of the bearing capacity of the subsoil, it is customary to use the classical empirical equations by Brinch-Hansen, modified for the angle deviation of the vertical loading by Meyerhoff. In literature, different solutions are known, sometimes only slightly different if the deviation from the vertical loading is small. However, the more the horizontal loading becomes important, the more these slight differences may lead to different results. An alternative is to use numerical analysis, e.g. Plaxis in order to evaluate the applicability of these empirical models, for this type of structure. Ultimately also 3D effects in the design might be

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analysed. Prof.drs.ir. J.K. Vrijling, Dr. ir. K.J. Bakker, ir . J. G. de Gijt

3D Analysis of Quay structures with a relief floor using embedded elements In the Rotterdam Harbour various different types of Quay walls have been constructed in the past years. One of these is a combined wall with a relief floor that reduces the soil loading on the deeper parts of the wall below the quay. One of the characteristics of this type of structure is the use of long MV type of stress anchors used to give anchor to the large horizontal forces on the structure due to the soil retainment. In modern 3D Finite Element analysis; e.g. Plaxis, a new development is the introduction of so-called embedded piles, which go straight through the mesh used for the analysis of the soil deformations. Special interfaces elements/relations are used to discount for the interaction with the soil. This study is aimed on an evaluation of the applicability of this type of elements for the design of the aforementioned quay-walls. Prof.drs.ir. J.K. Vrijling, Dr. ir. K.J. Bakker, ir . J. G. de Gijt

Functional design of Soil retaining structures

Different functional requirements may play a role in the design of a soil retaining wall, e.g. for a bank protection this may be erosion or even aesthetics (deformations). For an excavation; a building pit, this may be safety, water retainment, either temporary or for the long run. In the proposed study the challenge is to: 1) Develop an unambiguous 'product model' for a retaining wall, based on the various different requirements that may play a role. 2) do research on the influence of parameter choice for the customary design models (or models of analysis), on the predictability of the Serviceability Limit state (deformation criteria). Engineering experience more or less indicated that the presently used design models overestimate deformations. 3) To do research on the applicability of improved constitutive models to derive a better prediction of deformations. Prof.drs.ir. J.K. Vrijling, Dr. ir. K.J. Bakker, Ing. H.J. Everts Soil parameters for the design of piled guidance structures For the design of guidance works it is customary to use the computer program TILLY/BOTS to analyse the dynamic behaviour of the structure. In practice it appears to be difficult to derive the representative parameters for the design. It is thought that in engineering practice this may lead to a (too) conservative design approach. The project will be in cooperation with the structural engineering division of Rijkswaterstaat. Prof.drs.ir. J.K. Vrijling, Dr. ir. K.J. Bakker, ir. Vrijburcht

Standards for the maintenance management of quaywalls in the Port of Rotterdam

Problem definition: Quaywalls are very important assets for the Port of Rotterdam, because they are the hart of the port, where transport modalities meet each other. The quays facilitate the berthing of ships, the transhipment, storing and transport of goods by road, railroad, inland vessels or pipelines. The total amount of quaywalls is about 75 (!)km. Quay walls ask for a huge investment of about 15-20 million Euros per berthing place and so need any after-care in the way of inspection and maintenance to reach their design life of 50 years or more. Fortunately quay walls are robust structures, though designed in two dimensions they actually bear their loads in a three dimensional way, so local overloading or weakness will mostly be compensated in combination with any extra settlements. Yet in the course of time there may be some serious loss of strength and stability possible, because of degradation mechanisms like corrosion, chloride penetration, scour, etc.

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In that cases the problem for the maintenance manager is how much degradation in combination with some overloading is acceptable, with regard to functional requirements and remaining lifetime. Scope of work: So the Port of Rotterdam needs a set of standards and a formalised receipt based on requirements of all relevant stakeholders to judge the ageing quaywalls and their decisive parts not only for safety, but also for serviceability, durability, etc. Prof. J.K. Vrijling, Prof. A.C.W.M. Vrouwenvelder, Ir. A. van der Toorn, Ir J.G. de Gijt

Design of the hydraulic infrastructure for a ‘blue’ energy plant at the mouth of the river Rhine. The assignment for this study is the design of an osmotic power plant with the adjacent hydraulic structures on the 2e Maasvlakte or near the sluices of the Haringvliet.

Starting point of the study is a feasibility study by Rijkswaterstaat on blue power in the Afsluitdijk.

The study should be performed under the guidance and at the office of Rijkswaterstaat Bouwdienst, department of Hydraulical Engineering and Environment in Utrecht.

More information via this link Blue energy plant Blackboard versie.pdf or: Ir. H. van Duivendijk (TU Delft, Energiewaterbouwkunde), Drs L.A. van Geldermalsen (Rijkswaterstaat Bouwdienst)

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5. Finance and risks PhD Project: Parisian Options Parisian options are exotic options where the payoff at maturity depends not just on the value of the underlying asset at maturity, but also at its values during the contract's life. For example a Parisian knock-out call option is an ordinary call option that knocks out if the value of the value of the asset is above some given barrier during some time period of given length. It is also interesting to consider early-exercise features for this option. PhD Project: Asian Options There are discrete time algorithms known to price Asian options in binomial trees. Is it possible to develop also fast discrete time algorithms for asset price models with jumps. PhD Project: Chaos Expansions in Finance In engineering applications chaos expansions can be used to analyze non-linear dynamic problems. This type of analysis could be useful to study uncertainties in parameters in given models.

6. Aerospace Engineering

PhD Research Proposals by the Design of Aircraft and Rotorcraft (DAR) group of the Faculty of Aerospace Engineering, Delft University of Technology The mission of DAR To advance the design of and design methodologies for complex systems, in particular air transport vehicles and their flight trajectories by exploration of -new technologies to obtain novel or improved solutions, -the advances in flight physics to improve the prediction and simulation of the behaviour of complex aeromechanical systems, especially rotorcraft and wind turbines, and -advanced mathematics and informatics to improve the quality and effectiveness of the design process. The knowledge and competences within DAR are grouped in three areas I. Design; the synthesis of technologies II. Flight mechanics/dynamics; the synthesis of models III. Methodologies/Multidisciplinary Analysis and Optimization (MAO): the systematic

(computational) support of design including Systems Engineering, Operations Research, Multi-disciplinary Design Optimisation and Knowledge Based Engineering

PhD topics 1) The development of a flight mechanics model for performance calculations on the Delft ornicopter

(a tail-rotor-less rotorcraft that uses forced flapping to propel its blades about the hub and to provide yaw control).

The DAR group is developing a new type of helicopter, a tail-rotor-less one. Advantages of the concept are: less power consumption, reduced weight and improved safety. A second generation scale model is being built within the group to verify the basic concept including the directional control in free flight. One of the next steps is the creation of a high fidelity flight mechanics model of the

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ornicopter to substantiate the performance and flight handling quality analysis. The model will be created in the DAR Flight Tool Box. This existing tool, mainly for fixed wing aircraft, will be extended within the PhD project with kinematic, aerodynamic and structural models. 2) Extended application of knowledge based engineering to bottom up costing in engineering The DAR group has created a basic framework for cost engineering. The framework combines a so-called multi-model generator (a KBE application) that implements a generative product model that generates essential information for accurate cost calculations. The first version focused on manufacturing times. A database of parametric manufacturing processes was used to evaluate the cost, expressed as time, of some typical aircraft components. In the next generation framework the manufacturing database will be extended and the tool will be required to generate both manufacturing times and costs. 3) Development of a high fidelity noise generation and propagation model for aircraft trajectory

design. DAR is working on two innovative fixed wing aircraft concepts, the Blended Wing Body and the Prandtl plane. The evaluation of the aircraft noise emissions should be done with realistic generation and propagation models. Current models assume noise source strength based on statistical data. This will not work for new aircraft configurations, and therefore a first principle model will be developed, coupled to a proper noise propagation model. Aerospace Management and Operations (AMO) PhDs with China Value Engineering is the main research competency within AMO with application to three main research programmes that would be of interest to China’s growth in the aviation industry:

a) Production and Supply Chain Management b) Air transportation: including Airlines, Airports and Air Traffic Management c) Service Support: including Maintenance, Reliability and Safety

Some examples of Value Engineering research projects of include: 1. Integration of manufacturing cost modelling into the aircraft development process: Manufacturing

cost modelling using the Genetic-Causal Methodology can be applied to materials, manufacture, assembly, and process support in order to drive value driven design. The design process is essentially driven by value added (whether in terms of product, operations or support costs) rather than only using decision making that satisfies hierarchical design requirements. The cost models use causal models with variables that are used in the design process so that for example the costing architectures and design architectures can be easily coupled.

2. Production and operations cost modelling for improved life cycle analysis, including development and build, and airline, airport, air traffic management and maintenance: Life cycle cost modelling using the Genetic-Causal Methodology can be applied to the through-life assessment of cost materials, manufacture, assembly, and process support in order to drive value driven design. This can highlight big opportunities for specific operations cost optimisation and reduction at an air transportation level (airline, airport, air traffic management and maintenance) while also feeding back into the design process to improve aircraft design for operations and cost effectiveness.

3. Strategic alignment of supply chain partners for improved value chain management: A collaborative decision making methodology has been developed which identifies 31 key alignment factors. These can be used to analyse where supply chain partners are well aligned, where there is non-alignment and ultimately where better alignment can make the biggest impact on their associated business and operations processes. The factors of alignment are modelled into an evaluation system that allows relevant analysis in terms of both current performance and improved alignment and impact. Operations process consideration also highlights where there will be the biggest impact from alignment as well as the areas of less collaboration impact but individual priority.

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4. Strategic alignment of air transportation stakeholders for improved operations processes: A collaborative decision making methodology has been developed which identifies 31 key alignment factors. These can be used to analyse where air transportation stakeholders are well aligned, where there is non-alignment and ultimately where better alignment can make the biggest impact on their associated business and operations processes. The factors of alignment for the airline, airport and air traffic management stakeholders are modelled into an evaluation system that allows relevant analysis in terms of both current performance and improved alignment and impact. Analysis of air transport operations also highlights where there will be the biggest impact from bilateral or trilateral alignment as well as the areas of less collaboration impact but individual priority.

Space Systems Engineering: Prof. Gill Title Miniaturized Magnetically Levitated Reaction Ball for Attitude

Control

Contact TU Delft Prof.Dr. E.Gill, Dr Chris Verhoeven, Dr Jian Guo

Short description Reaction wheels are widely used on spacecraft as important attitude actuators. However the traditional reaction wheel suffers from many disadvantages such as friction and stiction, and the sensitivity to temperature. In the PhD study, a novel concept based on Reaction Balls shall be investigated. The proposed reaction ball is magnetically levitated on a basement where several actively controlled magnetic poles are available. The most important advantage of the reaction ball is that it can deliver high-precision momentum in any direction similar to the properties of the Control Moment Gyro (CMG) but avoiding the complicated mechanical structure and mechanisms. The reaction ball also has many other promising properties such as increased lifetime, increased output torque. The objective of this PhD work is to further develop the reaction ball concept and to engineer it through the development of a ground prototype. Some challenges, such as quick demagnetizing and re-orientation, the miniaturization, need to be studied, analyzed and solved during the PhD research.

Title Inter-Satellite Link for Small Satellite Formation Flying Mission Contact TU Delft Prof.Dr. E.Gill, Dr Jian Guo

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Short description TU Delft is cooperating with Chinese Tsinghua University on developing a joint small satellite formation flying mission called FAST (Formation for Atmospheric Science and Technology demonstration). One of the objectives of this mission is to demonstrate the inter-satellite communication in an open architecture, which requires a reliable inter-satellite link. The objective of this PhD project is to incorporate up-to-date technologies for allowing seamless interoperability and connectivity between multiple small satellites using Commercial-Off-The-Shelf (COTS) components. This project will investigate the performance of wireless protocols for inter-satellite application, and develop an inter-satellite communication platform that integrates RF devices with optimized protocol. The outcome of this project will also be applied to the fault-tolerant intra-satellite communication and benefit the research on fractionated space systems.

Title Research on Fractionated Space Systems Contact TU Delft Prof.Dr. E.Gill, Dr Jian Guo

Short description Using multiple, distributed small satellites to achieve the functional capabilities of a conventional monolithic big satellite is a trend for next generation space systems. However recently there is another concept, called Fractionated Spacecraft, attracts more and more attentions. The idea of the fractionated spacecraft is to reconstitute the functionality of a traditional satellite by a cluster of wirelessly interconnected spacecraft modules that fly in approximately the same orbit while flying freely in space. Unlike “traditional” distributed satellites, each fractionate module contributes a unique capability, which offers a level of flexibility and robustness in space. The objective of this PhD project is to further develop the idea of the fractionated spacecraft. There are several interesting research topics available, such as the wireless inter-modules communication and power transfer, the autonomous self-forming networks, the cooperation between modules. The PhD student is expected to collaborate with other students who are working on distributed computing and inter-satellite link, to demonstrate his outcome through a ground prototype.

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7. URBAN DELTAS

COMPARING URBANIZING DELTAS OF ASIA AND EUROPE The project is part of a larger research-program on URBAN DELTAS, which focuses on economic development, urban growth and urban transformations in delta-areas, combined with the necessity of improving flood-defense systems and taking into account the environmental values of the estuaries. New spatial and hydraulic concepts are necessary because of expected effects of climate-change (rising sea-level, increasing discharges of rivers, increasing rainfall), urban and economic development, and new insights and standards concerning the ecological values of wetlands and estuaries. The project investigates the possibilities for creating new relations and combinations of urban and regional design, hydraulic engineering, urban management and ecology, in order to define perspectives on a sustainable spatial development. The focus of the project COMPARING URBANIZING DELTAS IN ASIA AND EUROPE will be on urbanizing deltas and coastal areas in Asia (especially Indian and SE-Asian deltas) and Europe, especially the deltas of Northwest Europe. The research should pay attention to: - natural conditions of different urbanized deltas concerning geomorphology, coastal

morphology, etc.; - specific urban patterns in delta and coastal areas; - effects of climate-change in different urbanized deltas, especially concerning expected

changes of sea-level, discharges of rivers and rainfall; - societal and technical conditions in different urbanized deltas concerning urbanization-patterns

and -processes; - possibilities, opinions and standards in different urbanized deltas concerning hydraulic

engineering, risk and safety approach; - possible and desirable new solutions and approaches, combining aims concerning

urbanization, economic development, ecology and safety, taking into account expected effects of climate-change.

PhD- candidates should be familiar with urban design, urban planning and theories on sustainability of urban design and urban planning. Coordinator: Prof.dr.ir. V.J. (Han) Meyer; Chair Urban Design - Theory & Methods TU Delft, Faculty of Architecture