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-   -   how to use symetry in my rectangle geometry? (http://www.cfd-online.com/Forums/fluent/42685-how-use-symetry-my-rectangle-geometry.html)

harry October 29, 2006 09:57

how to use symetry in my rectangle geometry?
 
i have a rectangle geometry with velocity inlet at the inlet(face 1) and outflow at the outlet(face 2) ,the other faces(faces 3,4,5,6) are wall. i want to use only 1/4 of my geometry by using symetry. how to do this? give me the procedure step by step best regards

Jason October 30, 2006 09:08

Re: how to use symetry in my rectangle geometry?
 
Cut the geometry into 1/4 and apply symmetry BCs...

harry October 30, 2006 14:03

Re: how to use symetry in my rectangle geometry?
 
how to apply this symetry? i use axis or surfaces? expain me please more best regards

Jason October 30, 2006 15:40

Re: how to use symetry in my rectangle geometry?
 
What exactly are you trying to do? If it's simply a 1/4 model symmetry then split the geometry into 1/4 and use symmetry planes on the appropriate walls. If you're trying to do 1/4 model periodic (a periodic system will allow "swirl" where a symmetric system won't) then you have to use interface BCs on the two internal faces and define them as a periodic interface in Fluent.

Good luck, Jason

harry October 31, 2006 16:26

Re: how to use symetry in my rectangle geometry?
 
it is simply 1/4 volume model symmetry but jason how to designate these symmetry planes? i have a rectangle geometry with velocity inlet at the inlet(face 1) and outflow at the outlet(face 2) ,the other faces(faces 3,4,5,6) are wall. i want to use only 1/4 of my geometry by using symetry. how to do this? give me the procedure step by step best regards

Jason November 1, 2006 06:45

Re: how to use symetry in my rectangle geometry?
 
If you have the full domain, then you have to split it and delete the portions you don't want. Now that you've got the correct domain, mesh the geometry. Then apply wall BCs to two of the faces and symmetry BCs to the other two faces. Since you've applied inlet and outflow BCs I'm assuming you know how to apply BCs. If there are BCs that aren't showing up in the list, make sure you've picked Fluent 5/6 in the solver menu at the top of the screen.

I highly recommend the Gambit tutorials. I know some universities make the documentation difficult to find, but do a Google search and you'll find lots of tutorials.

Good luck, Jason

harry November 1, 2006 11:17

Re: how to use symetry in my rectangle geometry?
 
what faces I must take them as symetry? longitudinal and transversal?is it true i have read the manuel but no success best regards

Jason November 1, 2006 12:09

Re: how to use symetry in my rectangle geometry?
 
Ok... how about an example...

I have a rectangular duct... it has a square inlet and outlet that are 2m on each side and the duct is 5m long. The origin is located at the center of the inlet and the axial direction of the duct is located along the X-Axis (therefore the inlet plane is located at X=0 and the outlet is at X=5m). I only want to model 1/4 of the geometry, so instead of modeling a 2x2x5m duct, I model a 1x1x5m block where the block is placed in the +Y+Z quadrant. I define the faces at Y=1m and Z=1m as walls. I define the faces at Y=0m and Z=0m as symmetry (because if you mirror these faces about the symmetry condition they will fill in the original 2x2x5m domain which was centered about the origin). I define the face at X=0 as my inlet and X=5m as my outlet.

Symmetry BC should always be parallel to the flow stream (the definition of a symmetry condition does not allow flow through it, so if you had flow moving towards the symmetry BC you can picture that a mirror image of the flow would be coming at it and this would cause the flow to turn and move perpendicular to the Symmetry BC).

Good luck, Jason

harry November 2, 2006 10:57

Re: how to use symetry in my rectangle geometry?
 
thankyou jason


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