UDS Boundary Conditions
 

I have a UDS that I defined using Macros, it is essentially a Poisson Solver with no inlet diffusion (mass flux off, diffusion Coefficient = 1). There are 2 velocity Inlets (bottom and left hand side) and 2 pressure outlets. The velocity inlet boundary conditions are set to an expression Static Pressure / 1[Pa] i.e the boundary of the UDS is the equivalent of the pressure solved here. The Pressure outlet is set to a 0 flux condition.

Unfortunately there appears to be significant issues in the formation of the boundaries which impact on my results. I have tried different ways to initialise and even using the UDS with inlet diffusion on but the behaviour does not perform as one would expect.



Because the Poisson solver performs as expected around the airfoil I can rule out an issue with the formation of my source term for the UDS and have narrowed this down to being a boundary problem.

your problem is unclear.

do you use parallel solver? take it into account,
increase iteration number
decrease under-relaxation factor for UDS
simplify model: put constant value as boundary condition (in inlet)