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Hello

I am considering the effects of mesh resolution on the simulated velocity fields and I have a query regarding scaling VELOCITY DIFFUSIVITY to mesh resolution. I don’t want to go the mesh convergence route since I want to be able to compare the effects of increased bathy resolution + better resolution of the coastline on the simulated velocities (and hence particle transport). I attach my cas file – it’s a simple tides only case, with TURBULENCE MODEL=1 for constant viscosity throughout.

For most direct comparison I vary my timestep for comparable CFL between the simulations with different mesh sizes, but how do I best scale my VELOCITY DIFFUSIVITY parameter between the simulations, please (assuming I need to)? I think I’m OK with other parameters within the model scaling with mesh resolution (as that’s kind of the point) but the CFL criterion certainly needs to be the same, and I suspect the diffusivity relative to mesh resolution to ensure I’m resolving flows at the same scales…

With thanks in advance
Sophie

Hi Sophie

I would say as you're using constant viscosity, there is no relation with the mesh resolution.
It could be the case if you use other turbulence models.


Changing bathy resolution and coastline leads you to changing the mesh and then it's become impossible to ensure the same CFL...

If you make a test with the mesh convergence you will have an overview of the only mesh size effect without changing mesh structure (as the coastline and the bathymetry will be the same).
In your case you couldn't ensure a perfect scale effect

Hope this helps