# Laminar simulation with Simple Algorithms and Coupled Algorithms.

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 April 26, 2013, 18:46 Laminar simulation with Simple Algorithms and Coupled Algorithms. #1 New Member   Yanming LIU Join Date: Jan 2013 Location: NJ Posts: 5 Rep Power: 6 Hello, everyone I am doing the laminar simulation of channel flow. I use pressure-based Simple Algorithms and Coupled Algorithms to simulate the flow (Reynolds number is 1000 and 2000) respectively. But there is velocity fluctuation in the case of Re=2000, Simple Algorithms. The flow in all the other three cases seems stable, including the case Re=2000, Coupled Algorithms. Why? Is this a sign of flow transition? I know it is difficult to simulate the transition with Fluent if you do not know the transition point. But how to explain this phenomenon? Thanks.

 April 30, 2013, 09:55 #2 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 13 If you are saying coupled algorithms are more stable, then this is not exactly a news! The transition typically is handled better by transition turbulence models or even Low Re models, have you tried them? OJ

 April 30, 2013, 10:54 #3 New Member   Yanming LIU Join Date: Jan 2013 Location: NJ Posts: 5 Rep Power: 6 Are there some turbulent transition model in Fluent? What's your meaning of Low Re model? Thanks for your answer.

 April 30, 2013, 11:02 #4 Senior Member   Join Date: Aug 2011 Posts: 315 Rep Power: 14 There are two transition models, transitional sst model and k-kl model. The low reynolds model needs to be activated via the TUI, something like /define/models/viscous/turbulen-expert You should check the user's guide yourself. However, personally I insist that the way of p-v coupling should not alter the physics of the flow, be it laminar, transitional or turbulent. You should try reducing the URF for the case of Re=2000 with Simple algorithm.

 April 30, 2013, 11:15 #5 New Member   Yanming LIU Join Date: Jan 2013 Location: NJ Posts: 5 Rep Power: 6 Thanks. I will try them right now.

 Tags algorithm, laminar, transition

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