CFD Simulations for Ships with Rotating Propeller - Self ...sgc2016.star-global-conference.com/sites/default/files/public_pdf... · STAR Global Conference 2016, March 7th-9th, Prague,

STAR Global Conference 2016, March 7th-9th, Prague, Czech Republic.

CFD Simulations for Ships with Rotating Propeller- Self propulsion, Cavitation & Ship radiated noise -

NMRI, Tokyo JAPANN.Sakamoto and H.Kamiirisa

1

http://www.aukevisser.nl/inter-2/id427.htm


2

Table of Contents

１．Background and objective２．Overview of CFD solver３．Test cases４．Computational setup５．Results and discussion６．Concluding remarks


3

1. Background

Propulsive performance of commercial vessels→ EEDI regulations (IMO)→ Design exploration in… Hull form Energy saving device Propeller

Powering estimationby CFD→ Complex geometry/physics Grid generation Propeller-hull interaction

over

over

Class NK Annual Fall Seminar (2012)

Kawakita et al. (2012) Japan Shipbuilding Digest (2013)


4

1. Objective: Propulsive performance

1：CFD analyses in… Resistance and self-propulsion Propeller open water

2：Validation in… Self-propulsion factors (SPFs) Local flow field in model scale

3：Estimate… Effect of energy saving device Accuracy of the present methods


5

1. Background

Propeller cavitation and noise→Marine environmental protection

Regulations→ICES CRR No.209 (1995)→IMO MEPC.1/Circ.833 on 2014.→For commercial ships, yet non-mandatory→Regulate SPL (ICES)→Regulate Kpi (IMO): Kp1≤3kPa, Kp2≤2kPa for CB<0.65Kp1≤5kPa, Kp2≤3kPa for CB>0.65

ICES

Kamiirisa and Goto (2005)

Merchant ship in St.Lawrence at 1 mile

(http://ocr.org/portfolio/shipping-noise/)

merchant-ship-passing-at-1-mile.mp4


6

1. Objective: Propeller cavitation and noise

1：CFD analyses in… Propeller performance Propeller cavitation

2：Validation in… Cavitation pattern Near field cavitation noise in model and full scale Feasibility of empirical formula with CFD

3：Understand… Present capability of CFD to ship radiated noise


7

2. Overview of CFD solver

STAR-CCM+® 10.06 (double-precision ver.) k-ω SST (all turbulent), DES for cavitation in fine grid

- Low Rn near wall treatment (y+~1) Cavitation model by Schnerr and Sauer (2001)

- NO hydrostatic component at this time VoF for interface capturing Overset for propeller rotation SIMPLE for v-p coupling MPI parallelization 2nd order in space Propeller rotation in… →3deg(self-propulsion), 1deg(cavitation) per time-step.


8

3. Test cases: Propulsive performance

Japan Bulk Carrier (JBC)Hull (model scale)

Lpp(m) 7.0

B (m) 1.125

d (m) 0.4125

CB 0.858

Propeller (MPNO.687)

Dp (m) 0.203

aE 0.500

P/D 0.750

Z 5

Blade section AU

Geometries and exp. data open to public at

http://www.t2015.nmri.go.jp/jbc.html

Energy saving duct at stern

Resistance and self-propulsion data

Local flow measurement by PIV

→ without/with propeller rotation!

http://www.t2015.nmri.go.jp/jbc.html


9

3. Test cases: Propeller cavitation and noise

Propellers for “TS Seiun-1st”

CP HSP2

Dp (m) 0.221 0.220

aE 0.650 0.700

P/D 0.950 0.944

Z 5

Blade section Mod. MAU Mod. SRI-B- Decreased pitch

- Tip-unloaded

HSP2 retrofitted after CP to reduce hull vibration

Both model and full scale measurement data

available.


10

4. Computational setup: Propulsive performance

Flow condition (based on CFDWS Tokyo 2015)(Fn, Rn)=(0.0, 7.46E+06), np(rps)=7.8(w.o. duct), 7.5(with duct)

Grid→trimmed cell, overset→”linear” scheme for calculatinginterpolation coefficients fromdonors to receptors.→”flux correction” activated.

Stator(hull) 2.02M

Rotator(prop.) 3.95M

Total 5.97M


11

4. Computational setup: Propeller cavitation and noise

Flow condition (based on Kudo et al. 1989)

Grid (sliding/overset)

np(rps) Rn(kempf) KT σn

CP20.0

6.5E+05 0.207 3.06

HSP2 7.0E+05 0.201 2.99

0.7Dp

(Hasuike et al. 2010)

Local refinement to resolve sheet and tip-vortex cavitation

Approx. 19M cells in total.


12

5. Results: Propulsive performance

Effect of the duct to resistance and SPFs

Ctmx10-3 Exp. CFD

w.o. duct 4.289 4.160

with duct 4.263 4.131

KT-identity method for self-propulsion analysis

• Relative difference very well predicted!→Contribute for further design explorations.


13


Thrust distribution (θ=0o, 24o, 48o), back side

• Pitch distribution can be increased up to r/R~0.6 for the propeller WITH duct. →np may decrease yet yields the same thrust.


14


Vortical structure

• Tip and hub vortices are the same.

• Flow separation at the bottom of the duct

→ wake gain→ valid in full scale?• Difference in vortices

behind the propeller→ effect of np?


15

Cavitation pattern (Void fraction=0.1)

5. Results: Propeller cavitation

• Sheet cavitation well resolved, TVC needs more resolution.• Phase & amplitude difference in Kp and Vc due to skew.

Nuclei radius=1.0e-6(m)

Nuclei density=1.0e+14(1/m3)

←Click to animate

CPHSP2_DESfine_ovs.avi

CPHSP2_DESfine_ovs.avi


16

Validation in cavitation extent

5. Results: Propeller cavitation

port starboard port starboard

Exp.data: Kurobe et al. (1983)

θ=0° θ=20° θ=40° θ=60° θ=0° θ=20° θ=40° θ=60°


17

Overview of the validation data (SR183 Final report)

5. Results: Propeller cavitation noise

Wire mesh wake

in model scale

B&K 8103

B&K 8103 Levkovskii’s scaling law (model to full)

Brown’s formula for empirical method

K: empirical const. (=163)

B: # of blade, Dp: prop.dia., AD: blade area

n=163rpm in full scale

σns= σnm

Geo-sym hydrophone location

Compute Ac/AD by CFD!


18

Direct estimation from CFD solution


Tonal noise well resolved.Relative difference between CP and HSP2 captured well in tonal noise.(∵Wake and sheet cavitation patterns are well reproduced.)Broadband noise are fair.(∵Bubble growth and collapse cannot be well resolved.)

Model scale

Full scale


19

Indirect estimation from CFD(model scale)+Brown’s formula


Brown’s formula gives appropriate upper-bound.(∵Ac/AD well predicted.)


20

Propulsive performance• Still needs diagnostics in POT (both exp. and CFD)• Relative difference in SPFs very well predicted with and

without duct configurations.• Local physics helps for design exploration.

Propeller cavitation noise• Sheet cavitation pattern well predicted.• Quantification of cavitation extent feasible by CFD.• Tonal noise well predicted.• Broadband noise fair, yet empirical formula is still useful

together with CFD.

6. Concluding remarks

Documents

CFD Simulations for Ships with Rotating Propeller - Self ...sgc2016.star-global-conference.com/sites/default/files/public_pdf... · STAR Global Conference 2016, March 7th-9th, Prague,