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-   -   Symmetry problem (http://www.cfd-online.com/Forums/flow-3d/82949-symmetry-problem.html)

 sameer10dulkar December 9, 2010 13:41

Symmetry problem

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.

-Sameer
http://img96.imageshack.us/img96/222/71724505.jpghttp://img205.imageshack.us/img205/1...mmetrymesh.jpg

 aginor January 17, 2011 21:07

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?

 sameer10dulkar January 17, 2011 22:53

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 (Post 290869) 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?

 jk75 January 18, 2011 04:52

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

 MuxaB January 19, 2011 01:37

Quote:
 Originally Posted by jk75 (Post 290909) 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.

 sameer10dulkar January 21, 2011 15:11

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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