GAMBIT: Specifying Boundary Conditions

fluentnoob · May 26, 2009, 13:25

Hey everyone.

I am trying to model the flow around a cylindrical body. I have the cylinder inside a cuboidal volume and I have attached a boundary layer and meshed the whole volume. Now, I have to specify the boundary conditions. I have specified the cylinder hull as a WALL and the left face of the cuboid as velocity inlet.

Could you please help me out as to what the right face of the cylinder will be (outflow / pressure outlet / pressure far field(what is this?))?
And also, what would the roof and the floor of the cuboid be? (walls?) They are actually free slip walls. How do I define this in gambit?

I am modeling this cylinder in deep water. Could you guys please help me out with this?

Thanks a lot!

prasad.ichal · May 28, 2009, 08:06

Do you know pressures? You can calculate the pressure at the required depth from the water surface. Then you may try using 'pressure outlet' at all the boundaries with direction as per the adjacent boundary cell. I won't advise using 'outflow' at the downstream boundary as the flow across the cylinder will lead to wakes and there may a certain numerical diffusion error be taking place from the outflow boundary.

Pressure far-field is used only when the fluid density is calculated from the ideal-gas law as in the compressible flow problems. It can not be applied to your case.

May 26, 2009, 13:25	GAMBIT: Specifying Boundary Conditions	#1
fluentnoob Member DT Join Date: May 2009 Location: Lisbon Posts: 37 Rep Power: 16	Hey everyone. I am trying to model the flow around a cylindrical body. I have the cylinder inside a cuboidal volume and I have attached a boundary layer and meshed the whole volume. Now, I have to specify the boundary conditions. I have specified the cylinder hull as a WALL and the left face of the cuboid as velocity inlet. Could you please help me out as to what the right face of the cylinder will be (outflow / pressure outlet / pressure far field(what is this?))? And also, what would the roof and the floor of the cuboid be? (walls?) They are actually free slip walls. How do I define this in gambit? I am modeling this cylinder in deep water. Could you guys please help me out with this? Thanks a lot!

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May 28, 2009, 08:06		#2
prasad.ichal New Member Prasad Dudhgaonkar Join Date: Mar 2009 Location: Chennai Posts: 9 Rep Power: 17	Do you know pressures? You can calculate the pressure at the required depth from the water surface. Then you may try using 'pressure outlet' at all the boundaries with direction as per the adjacent boundary cell. I won't advise using 'outflow' at the downstream boundary as the flow across the cylinder will lead to wakes and there may a certain numerical diffusion error be taking place from the outflow boundary. Pressure far-field is used only when the fluid density is calculated from the ideal-gas law as in the compressible flow problems. It can not be applied to your case.