# reversed flow

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 September 16, 2004, 01:01 reversed flow #1 Raj Guest   Posts: n/a Hi all, I am simulating a 2D axisymmetrical co-axial burner. The boundary conditions are mass flow rate at the inlets (both for oxygen and fuel) and outflow at the outlet. But i get the message as "reverse flow in faces" and "turbulency viscosity limited to viscosity ratio" while iterating and process was completed in 26 iterations. Can anyone help me out. TIA

 September 16, 2004, 09:54 Re: reversed flow #2 Twiti Guest   Posts: n/a Try to impose proper boundary condition at the inlet an outlet, and increase the upper limit of the turbulency viscosity. According to my own experiences, you can try a less mass flow rate at the inlets, and increase them to the values you want after you got an initial solution.

 September 16, 2004, 22:39 Re: reversed flow #3 Ng Khai Ching Guest   Posts: n/a Hi: I am developing the 3D compressible unstructured code. When I try to run it in a diffuser, backflow occurs at pressure outlet. Could you pls advise on how to treat backflow? Which variables we need to fix or extrapolate? Pls help. Thanks. -khai ching-

 September 17, 2004, 02:08 Re: reversed flow #4 nabeel Guest   Posts: n/a hi, in my experience u try outflow condition at oultlet.or give some uniform area at outlet boundary to stabilise flow. nabeel

 September 17, 2004, 02:27 Re: reversed flow #5 Ng Khai Ching Guest   Posts: n/a Hi: In fact, there should be no backflow at the pressure outlet in the converged solution. But, backflow occurs during the iteration. As mentioned in FLUENT user guide, backflow total temperature is specified. Apart from the total temperature, what other variables we need to fix/extrapolate to avoid backflow in the subsequent iterations? pls advise. -khai ching-

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