# reverse flow

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 May 24, 2005, 01:54 reverse flow #1 kiao Guest   Posts: n/a I am a total newbie so please understand... Trying to simulate sprays. So I set up a simple box 1mx0.6m 2D domain as sprays don't travel that far with a surface opening at the top at 0.1m. Inlet velocity =1m/s entering at the surface opening. I set turbulence model k=1.0, e=0.5 This works fine, and then I try vel = 20m/s and get reverse flow. Do I have to extend the domain or change to unsteady flow to simulate the spray.

 May 24, 2005, 03:47 Re: reverse flow #2 kawthar Guest   Posts: n/a I think before to make unsteady flow, try to extend the domain in the downstream and for precison change the options of k-e model. You use now k=1 (Default value by fluent) so try to use (I and Dh ). For I use an estimate value from the expression in doc of fluent ( Imax=10%) and Dh = 2* Length in you case 2m. And let us know if it will be OK

 May 24, 2005, 22:44 Re: reverse flow #3 kiao Guest   Posts: n/a extended the domain Dh (Hydraulic Diameter?) = 2. That actually made it worse than the original k-e settings. It converges at k=1, e=0.05. Whenever I reduce the opening i get reverse flow. Is it because the flow is entering an open flow field causing reverse flow which rebounds off the adjacent wall (wall parallel to the opening) geometery --------ooo-------- I I I I I I I I I I I I -------------------

 May 26, 2005, 14:06 Re: reverse flow #4 us Guest   Posts: n/a I hope you know to set different Dh depending on the hydraulic dia of pipe inlet/outlet. for example, in your case, spray hole dia is, 0.1m or so. Means, you can't define Dh=2 there. -US

 May 26, 2005, 14:08 Re: reverse flow #5 us Guest   Posts: n/a Also, I is aproaximately 4% for Re=50000. So, adjust that value accordingly.

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