Handling Vessel Data

Slide 1 of 14www.orcina.com OrcaFlex User Group, 2010

Handling Vessel Data

Introduction

• The vessel object is complicated

– Different calculation options

– Different data types

required from varied

sources

• Guidance on how to import the different data types required



Overview of Vessel Data

3 main methods for importing diffraction data:

• Manual: Copy/paste (not advised!!)

• Semi-automatic: Marked-up text file

• Fully Automatic: AQWA and WAMIT

This data is manually set



Units and Conventions

• OrcaFlex has its own units and conventions system. Diffraction data may have different units or conventions

• AQWA / WAMIT import: data automatically converted to match OrcaFlex units and conventions at time of import

• For marked-up text files:– If units and conventions are specified then

OrcaFlex converts these as above

– If units and conventions are not given then the data is imported unconverted



RAO Data Import

• Either Displacement or Load form

• AQWA / WAMIT files:

– read by OrcaFlex (‘Import Hydrodynamic Data’ button)

– either .lis (AQWA) or .out (WAMIT) file (note that

WAMIT .sif file is not supported)

• Otherwise you need a ‘marked-up text file’,

with appropriate header for data type:

– *** OrcaFlex Displacement RAO Start ***

– *** OrcaFlex Load RAO Start ***

• Use ‘Check RAOs’ button for sanity check



Wave Drift (QTF) Data Import

• Again can be imported either:

– From a full AQWA/WAMIT import

– Or from a marked-up text file

• Previous releases required non-dimensional

QTF data

• In v9.4 QTF data must be dimensional:

– Units are specified in the marked-up text file

– Old binary (.dat) OrcaFlex files will be

automatically converted



Stiffness, Added Mass & Damping

• Again, data is either:

– Imported directly from AQWA/WAMIT

– Or from a marked-up text file

• OrcaFlex requires dimensional data. Source

data often non-dimensional or different units:

– AQWA / WAMIT handle automatically at import

– Marked-up files. Conversion is done with scaling

factors in the marked-up file. Examples for

MOSES, ARIANE/HYDROSTAR and WADAM in

v9.4 help



Structure

• Much less data is required here

• Mass and mass moments of inertia:– AQWA / WAMIT automatically set if available

– For a marked-up text file, these need to be manually added

• CoG:– OrcaFlex uses this as a common reference origin

for AQWA / WAMIT import so must be manually set

– For a marked-up text file, this is not set and needs to be manually added



Hydrodynamic & Wind Damping

• This data is not automatically imported (but

much less data required here)

• So copy/paste or manual entry

• Loads due to relative flow past the vessel

• Data sources:

– OCIMF (Tanker vessel forms, with minimal topsides)

– Wind tunnel tests (both above and below waterline)

– Semi-analytical or CFD methods



Drawing

Visual only, no impact on calculations or results

Import from .x file in

shaded views

Copy/paste or

manual entry



Things to look out for…(1)

AQWA / WAMIT:

• Set CoG location in OrcaFlex before import

• Symmetry convention must be set manually

• Equilibrium position:

– Must be set manually for WAMIT import

– Z-position imported for AQWA but not heel/trim

• Import file should have single vessel data

• Some AQWA / WAMIT files not in format

OrcaFlex expects. OrcaFlex warns and may

not import



Things to look out for…(2)

Marked-up text files:

• Some data needs to be set manually:

• With forward speed, Moses/Ariane present

encounter frequency. OrcaFlex needs zero-

forward speed data

• Hydrostar recently introduced a WAMIT

output format.

RAO, QTF and Phase Origins Stiffness Matrix

Symmetry Convention Equilibrium Position



Marked-Up Text File Example(s) …(1)

There are examples of how to mark-up the data

for some common diffraction packages in the

OrcaFlex help, see:

System Modelling – Data and Results | Vessel Types |

Importing …. (there are a few different pages covering

the different data types)

A typical generic file is shown in the next slide



Marked-Up Text File Example(s) …(2)



Summary

• If you have data from AQWA or WAMIT data

then simply import these directly

• If you have data from another package then

used marked-up text files:

– These can be imported individually on each

vessel type data form

– Or you can merge all the individual text files into

one large text file and import directly through the

‘Import Hydrodynamic Data…’ button

Documents

Handling Vessel Data