Use of OpenFOAM in Modelling of wave-structure interactions

Lifen ChenSupervisors: Dr JunZang, Dr Andrew Hillis, Prof Andrew PlummerArchitecture and Civil Engineering departmentUniversity of Bath lc499@bath.ac.uk

Bath HPC symposium 4th, June, 2013Bath, UK

Background

Ocean waves: wind generated waves

Irregular waves

Intermediate and deep watersApproximations

Regular waves: sine/ cosine function

Background

Wave motion: Wave amplitude/elevation Water depth Wave length

Background

Background Computational Fluid Dynamic (CFD): OpenFOAM

Open Source C++ library

Suitable for use in wide ranges of problems

Parallel processing capability of OpenFOAMDefault

Domain decomposition

openMPI

Terminal commands decomposePar

mpirun --hostfile <machines> -np <nProcs> <foamExec> <otherArgs> -parallel > log &

reconstructPar

Cases

Computational domain:

30m × 2m × 1.01m (half domain)

8 cases: various wave parameters

Zang, J. and Taylor, P. H etal.(2010)

Steep wave and breaking wave impact on offshore wind turbine foundations—ringing revisited

25th IWWWFB, China

Computational Cost (Multi-cores)

Cells: 15712120Cores: 4 coresComputational time: 5 daysSize of output files: 90GB

Cases: ?Static mesh Dynamic mesh

Results

Has been applied in ocean engineering successfully.

Can predict wave loading on the fixed structure correctly.

In adaptions of the source code…

A series of trials: Boundary conditions mesh type and resolution wave parameters…..

Running in parallel (Aquila)OpenFOAM-2.1.0 vs. OpenFOAM-1.5

PC vs. Aquila

testing

1. Boundary conditions:

attempted: totoalPressure for output boundary PC: stable Aquila: dump after 7s

modified to: zeroGradient PC: stable Aquila: stable

2. Running the case PC: 4 cores Aquila: 4 processors

Running in parallel (Aquila)

t = 5s

t = 10s

t = 15s

t = 20s

t = 25s

Green line : PC results, red line: Aquila results

Future work Simulation interactions between waves and

floating bodies. dynamic mesh

Simulation interactions between waves and real WECs.

complex geometries and structures’ shape

Increase computational cost

Thank you!