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Back flow problem in gas cyclone

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Old   August 31, 2012, 04:27
Default Back flow problem in gas cyclone
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Hi.
I'm working on Stairmand high efficiency cyclone model. I have a problem that I am getting back flow in the central region, from vortex finder. I am using unsteady RSM model with standard wall function (I have also tried the enhanced wall treatment option); with velocity inlet for inlet, outflow for flow outlet, and walls for dustbin and other walls as the Boundary Conditions. For pressure-velocity coupling I am using SIMPLE (I have also used SIMPLEC). For others it is PRESTO, QUICK, 2nd order, 2nd order. For RSM it is 1st order. I'm using Fluent v14, and I have meshed using GAMBIT as well as ICEM CFD, but I am getting the same results. The tangential velocity profile is fine. My problem is the back flow at the outlet (vortex finder). I am still struggling with single phase flow (no Discrete Phase Model introduced yet).

Can anybody please help me to get rid out of it. I have also tried to extended the outlet (vortex finder) length upto 5 times the diameter so that the flow is fully developed and there is no back flow, but still the results are same.

Do I need to work on some coding (in the form of .udf) to eliminate this?

I am stuck to this problem since last 3 months. Looking forward for your positive response.
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File Type: jpg Axial Velocity contour.jpg (76.5 KB, 30 views)
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