Normal velocity at the symmetry boundary

Seventy · October 20, 2009, 12:38

Hi, I am new to Fluent but have some background on fluid mechanics. I notice a problem in Fluent and don't know how to explain it. I have a 3D k-e model with a symmetry boundary. The velocity normal to this boundary should be zero according to the definition of symmetry, but the converged solution shows none-zero normal velocity exists on this surface. A similar case is the OUTFLOW boundary. By definition, OUTFLOW boundary should have zero normal flux, but I observed none-zero normal velocity gradient in a contour plot on the surface. Could anyone explain the reason please?

regards,
Steve

t.krishnamohan · October 26, 2009, 06:52

Steve,

When a boundary is defined as symmetric, the gradients of all the properties normal to it will be zero. You are misunderstanding the properties with its gradients.

October 20, 2009, 12:38	Normal velocity at the symmetry boundary	#1
Seventy New Member Join Date: Oct 2009 Posts: 1 Rep Power: 0	Hi, I am new to Fluent but have some background on fluid mechanics. I notice a problem in Fluent and don't know how to explain it. I have a 3D k-e model with a symmetry boundary. The velocity normal to this boundary should be zero according to the definition of symmetry, but the converged solution shows none-zero normal velocity exists on this surface. A similar case is the OUTFLOW boundary. By definition, OUTFLOW boundary should have zero normal flux, but I observed none-zero normal velocity gradient in a contour plot on the surface. Could anyone explain the reason please? regards, Steve

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October 26, 2009, 06:52		#2
t.krishnamohan Member Krishna Join Date: Oct 2009 Posts: 34 Rep Power: 16	Steve, When a boundary is defined as symmetric, the gradients of all the properties normal to it will be zero. You are misunderstanding the properties with its gradients.