Boudnary conditions in couple of Navier-stokes and thermal advection-diffussion

[POSThu]

Hi, all

I am trying to simulate the non-isothermal airflow field in a room; however, the simulation is always diverged. I think the reason may be related to the boundary conditions. I used

setLocalVelocityBoundary<T,NSDESCRIPTOR>(NSLattice, NSomega, superGeometry, 3);
setLocalPressureBoundary<T,NSDESCRIPTOR>(NSLattice, NSomega, superGeometry, 5);
setAdvectionDiffusionTemperatureBoundary<T,TDESCRIPTOR>(ADLattice, Tomega, superGeometry, 3);

, but the temerature around the pressure outlet is always low, and the air inflow the room from the pressure outlet.
I have read some paper, and the regularized boundary approach for pressure and velocity boundary conditions has been used. I wonder how to use that? I didnot see some function like setRegularizedvelocityBoudnary, but there are RegularizedVelocityBM and RegularizedPressureBM, how to use those? Could anyone give me a example? Thanks a lot.

Best Regards,
mengqiang

[mgaedtke]

Hi mengqiang,

the setLocal*Boundary functions are in deed using the regularized boundary formulations. For additional stability, I would suggest using the interpolation versions of those.

For pressure outlets, I recommend to use the local convection boundary for the according temperature field. Make sure to execute the coupling operation on those material numbers as well.

Also check your relaxation time and lattice velocity to be in the stable regime. In Timm Krüger’s book on LBM, there is a chapter on how to choose these parameters consistently.

Best regards,
Max

[Author]

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