# Symmetry problem

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 December 9, 2010, 13:41 Symmetry problem #1 New Member   Sameer Tendulkar Join Date: May 2010 Posts: 11 Rep Power: 9 Sponsored Links I was trying to use symmetry to reduce simulation time taken by Flow 3d to simulate flow through t shaped microchannel. When i meshed only the right half of the microchannel geometry(see picture attached) as opposed to the full geometry (see picture attached ) i am getting different results. I have used the same mesh Density and same boundary conditions. Inlet BC: Q=1ml/min Outlet BC: P=1 atm SI Units are used for the simulation and the simulations were run until steady state condition. The output graphs for pressure show a difference of 50 pascals at the stagnation point. Is this okay? or did i miss out on some parameter for getting the difference in value. Thanks in advance. -Sameer

 January 17, 2011, 21:07 #2 New Member   Nikolaidis Giorgos Join Date: Jan 2011 Posts: 4 Rep Power: 8 i think that your flow is not simmetrical! think about a vortex. in some cases it looks symmetrical but it is not. the diference of 50 pascal is in the aqurancy that you whant?

January 17, 2011, 22:53
#3
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Sameer Tendulkar
Join Date: May 2010
Posts: 11
Rep Power: 9
50 pascal is the difference in the pressure values just near the outlet of the T junction for the two cases. I am not sure if that is okay or how much that would affect the final output?

I am currently running for symmetry in the plane of the t junction (as opposed to the perpendicular plane as shown in the fig).

Quote:
 Originally Posted by aginor i think that your flow is not simmetrical! think about a vortex. in some cases it looks symmetrical but it is not. the diference of 50 pascal is in the aqurancy that you whant?

 January 18, 2011, 04:52 #4 New Member   Johannes Köpf Join Date: May 2009 Location: Germany Posts: 29 Rep Power: 10 Hello, you are using the same inlet BC in both cases although the inlet surface area in the second case is only half of that of the first case? Doesn't this affect the volume flow rate? Regards, Johannes

January 19, 2011, 01:37
#5
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michael barkhudarov
Join Date: Mar 2009
Posts: 332
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Quote:
 Originally Posted by jk75 Hello, you are using the same inlet BC in both cases although the inlet surface area in the second case is only half of that of the first case? Doesn't this affect the volume flow rate? Regards, Johannes
Good point! The inlet flow rate needs to be cut in half when modeling a half of the domain.

 January 21, 2011, 15:11 #6 New Member   Sameer Tendulkar Join Date: May 2010 Posts: 11 Rep Power: 9 Hi Johannes and MuxaB, Thanks for the inputs. I will run it with the changed conditions. I appreciate your help. -Sameer

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