Surface Elevation Rise when using DDT
I've recently been looking at large scale 3D wave simulations at low resolution (dp = 1.0 metre). I am using the Relaxation Zone method and have used the RZ examples as a base to build on, which includes the Density Diffusion Term. I have noticed that although the drift correction maintains an approximately constant number of particles in the domain, the water level continues to rise (figure attached). I noted that without the DDT, this rise essentially disappears however surface elevation measurements become less accurate. I have tried 2D simulations with increased resolutions however the magnitude of the water level rise just reduces with more particles. This appears to be a problem only near the surface. Is there any way to prevent this phenomenon while still using the DDT? My starting water level is 16 metres, I am limited to 1 metre dp due to the size of my domain.