An open source CFD solver,OpenFOAM®
, has been used to create a numerical wave tank.
The study is based on the interFoam solver, i.e. a solver for incompressible multiphase
flow problems. The solver uses the finite volume method for the spatial discretization of
equations and applies the VOF approach for the free surface modeling.
Initially a convergence study was carried out. The study was based on the propagation of
fifth order Stokes waves in deep water condition. To this end two separate applications,
waveWriter and errorCalculator, were created. With the former the initial conditions for
the velocities and pressure of fifth order Stokes wave can been specified directly for interFoam.
The errorCalculator is a post-processing tool that estimate the computational
errors at each time step. The study revealed that the model exhibits only first order
convergence. The loss of one order is due to the waveWriter setting only first order initial
Wave generation and absorption in the wave tank are performed by the relaxation method.
For this purpose the existing interFoam solver has been partially modified in order for
replacing the computational solutions with desired analytical ones inside the relaxation
zones. In this manner the modified solver is able to generate and dissipate different wave
types in the numerical wave tank. It is shown that outgoing waves are absorbed efficiently
by extending the damping relaxation zone to at least three wavelengths, while
one wavelength extension is required for the wave-generating zone.
To validate the numerical wave tank, the Whalin shoaling test was considered. Unfortunately,
inadequacies in the then existing version of interFoam, (version 1.6.x), in the
handling of the pressure force balance on non-orthogonal and distorted meshes, hindered
and finally stopped the validation test process. Subsequently it was found that the newer
version OpenFOAM-1.7.x, can be used promisingly for the validation of wave tank by
Whalin test and this has been defined as a recommended future work.
Master of Science Thesis
- Numerical Wave Tank
- Nonlinear waves
- Free surface flow
- Relaxation Method
- Wave Generation and Absorption