[ewissmach]

I am currently running simulations for a submerged breakwater in FLOW-3D HYDRO. To find wave attenuation, I have probes before and after the structure that record free surface elevation. Since I have a wave outflow x-max boundary condition with a wave dampening zone, I expected the surface elevation to stabilize and remain at consistent values; however, my plots are showing that the overall surface elevation is increasing towards the end of my simulation. Does anyone know what would cause this error?

[Flow Science Australasia]

Have you tried going to Numerics --> Additional Options --> Eliminate net volume influx at wave boundaries?

More info from the documentation:

"During one wave period for all oscillatory waves, including Linear, Stokes and cnoidal waves, more fluid moves into the domain at the wave boundary than out of the domain. This is because fluid has a higher elevation when moving in than when moving out. Moreover, for Stokes and cnoidal waves, fluid moves faster at the wave crest than at the trough. This may result in a net increase of fluid volume in the domain over time in certain circumstances. As an option, users can choose to automatically compensate for the net fluid volume influx induced by the wave motion at the boundary by going to Numerics ‣ Wave boundary condition and checking Eliminate net volume flux."

[ewissmach]

Thank you very much! I appreciate the explanation as well. I will try that change in initial settings.