Session: 08-05-02 Free Surface Flows II

Paper Number: 80255

80255 - Solitary Wave Propagation Using a Novel Single Fluid Finite Volume Method for Free Surface Gravity Waves 

Accurate prediction of wave loads from extreme waves on offshore jacket structures are important to ensure the structural integrity. Failure of a single element may lead to a total collapse of the structure, which makes it important to predict the local wave load distribution on each structural element. Accurate load predictions are also important for assessing the fatigue life of individual members in the structure. CFD models considering wave load predictions are often validated against the global loads on the structure, which are important for the total stability, but this does not show that the CFD model can predict the load on the individual structural elements.

The local wave load distribution on a structural element is highly dependent on the wave kinematics, and since the largest velocities are found at the wave crest, it is important to have an accurate prediction of the surface elevation and the velocities.

The popular open-source CFD code OpenFOAM-v1912 have two solution algorithms (interFoam and interIsoFoam), which are traditionally used for ocean wave simulations and wave load predictions. The existing solution methods are based on the assumptions of a continuous solution around the free surface, however the application of the models to ocean wave simulations do often not align with the underlying assumptions with the consequence of inaccurate and unphysical predictions even for propagation of a constant wave. 

We have introduced a new solution method that only models the flow in the water region and applies appropriate boundary conditions at the free surface. The resulting wave kinematics and wave propagation is accurate and the behavior of our model is in line with the underlying physics. Simulating a still water level in an inclined square box emphasizes the current fundamental deficiencies of interFoam and interIsoFoam and shows the ability of our numerical method to handle this simple, yet numerically challenging case. A test case with a solitary wave shows the performance of both the existing and new methods.

Presenting Author: Jesper Roland Kjærgaard Qwist Technical University of Denmark

Authors:

Jesper Roland Kjærgaard Qwist Technical University of Denmark
Erik Damgaard Christensen Technical University of Denmark