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sam July 19, 2003 04:15

How to resolve boundary condition problem?
Hello Fluent User,

I am doing numerical analysis in fluent for an incompressible flow and i have some problem assigning the boundary conditions to the computational domain. well i have applied the WALL boundary condition on the body and at inlet velocity inlet and at outlet pressure outlet condition is applied.Well now i don't know what boudary condition should be applied at the outer face of the domain, if i use the pressure far field condition it gives an error saying that "Divergence in AMG solver x-momentum failure".while my free stream flow direction is in z-direction. If i export the 3d mesh without applying any boudary condition on the outerface it take it as a wall so in fluent i have two wall boundary conditions which is not true.Please help me how can i solve this problem. Thanks in advance!

gelislim July 19, 2003 17:41

Re: How to resolve boundary condition problem?

Pressure far field bc is for compressible flows so it requires using ideal gas law as density specification method.If you dont use ideal gas law, it is normal to have the error you mentioned. So if you change the density specification method to ideal gas law,the problem will probably vanish. This time, however, another problem may lead you to an erroneus solution.The problem is that velocity inlet boundary condition is suitable for "only" incompressible flow.So I suggest you to choose your outer boundary far enough from the immersed body and use velocity inlet(if flow is incompressible) boundary condition at this boundary. Choosing the outer face so that flow "always come into the domain" will probably help convergence.

Good Luck

sam July 20, 2003 02:19

Re: How to resolve boundary condition problem?
Thanks for your help dear gelislim.

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