reversed flow

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 November 25, 2003, 11:48 reversed flow #1 amir Guest   Posts: n/a hi i recieved this message when fluent is trying to solve the problem " reversed flow ..... faces" do you know what's the problem?

 November 25, 2003, 17:02 Re: reversed flow #2 Paul Guest   Posts: n/a Hi I face the same problem. I am solving flow and energy equations for a air in hemi clyinder and fixing temperature profile on one wall. my outlet is outflow bounday condition. I get the warning 'reversed flow at face 2 at outflow'. I am still trying to figure out the reason for this problem. Amir, is your flow conditions similar to mine? Any help appreciated.

 November 26, 2003, 03:37 Re: reversed flow #3 Jeff Guest   Posts: n/a I don't know exactly where the problem come from, but it's sure you have a convergence problem. Check you made enough iterations and check your residuals. Another source of problem can be the your outlet is too near from your cylinder (in the case of Paul). The distance between your outlet and the cylinder should be at least 15 diameters. And try using a pressure outlet boundary condition. Regards. Jeff

 November 26, 2003, 03:52 Re: reversed flow #4 Louwrens Guest   Posts: n/a You're probably using pressure-outlet boundaries. On these you have to specify the backflow conditions for total pressure, temperature, turbulence etc, depending on the model. What you're getting is a message from fluent telling you that you don't just have outflow over your boundary but some inflow as well. Because the inflow conditions are calculated from the data you supplied, it might not be as accurate as when interpolated from the flowfield. Remember, it's never good practice to have reversed flow on the outflow boundary of your domain, rather move your boundary downstream...

 November 26, 2003, 07:46 Re: reversed flow #5 mateus Guest   Posts: n/a Hi! You can also make cells at outlet boundary very long and thin. This trick has a kind of damping function ang helps you get rid of reverse flow problem... Hope it helps MATEUS

 November 27, 2003, 07:25 Re: reversed flow #6 Trilok Guest   Posts: n/a what boundary condition u r using at the outlet??

 November 27, 2003, 13:10 Re: reversed flow #7 Paul Guest   Posts: n/a The boundary condition at the outlet is outflow. As jeff mentioned, i do face convergence problems whenever i get the reversed flow warnings.

 November 28, 2003, 04:45 Re: reversed flow #8 mateus Guest   Posts: n/a HI! Try it with pressure outlet. It's usually better for convergence. regards MATEUS

 November 30, 2003, 10:21 Re: reversed flow #9 amir Guest   Posts: n/a Hi My boundary conditions are the same as Paul.(out flow) thank yuo.

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