I set a wave simulation input file of Flow3D with a 0.7m Height wave incidence(i.e. wave amplitude is 0.35m),and the water depth is 2.0m in the area,the Finish time is set to 200s.then I render a probe data of free surface elevation from the result, I got a wave line of the water depth at this probe point, but the water depth of this point has a little decrease with the increase of time, in begeinning, the water depth is 2.0m and the wave heigh is about 0.6m, but in the end of the time, about 180s, the water depth is just about 1.2m, what's the reason of that?

where is the relative location of the probe point in the domain? is it very close to the downstream boundary? what kind of boundary conditions did you use in the simulation? if you use the outflow boundary condition at downstream in v9.3.*, did you check the box "Allow fluid to enter at outflow boundary"?

what about the elevation versus time at some point that is very close to the wave boundary?

The probe point is in the center of the domain, and I check the"Allow fluid to enter at outflow boundary", too. Could you sent me a email ,so I can post a image and sent you.

Regards!

so have your checked the point that is somewhat close to the wave boundary?

please try extending the domain in the downstream direction and applying the split lagrangian VOF method, to see if there is any difference.