Free surface for non-hydrostatic model?

[shriyafruitwala]

Hi all,

I am trying to simulate internal tides generated by barotropic tidal flow over complex topography in a closed domain. To do this, I would need a free surface to allow for the waves to propagate. I also want to resolve the mixing excited by these waves, so this would be in a non-hydrostatic regime. Would it be possible to allow for a free surface in the non-hydrostatic model with an immersed boundary? Thanks!!

[glwagner]

Hi @shriyafruitwala, I am wondering --- is there any way to formulate your problem by prescribing a vertical velocity at the top of the domain? If that is the case, it may be possible to use @jagoosw's open boundary implementation for this.

I also believe that linear free surface dynamics would be relatively straightforward to implement, since we can simply use the implementation in the hydrostatic model. There is a little code reshuffling required however and I also have to think if there would be an issues in computing the vertical velocity tendency on the top surface (eg k = Nz + 1) which is necessary for this. @simone-silvestri and @jm-c may have thought about this.

[shriyafruitwala]

Thanks for getting back to me! I think that would work in a pinch, but it would probably be cleaner to have the free surface capability.

[glwagner]

Well, I agree it would be simpler for users. I'm not exactly sure what adding a linear free surface to the NonhydrostaticModel would look like, eg how it interacts with the pressure correction. Perhaps @jmc knows.

I also wonder if BackgroundFields might be used to accomplish something similar to what I suggested without requiring an open boundary condition.