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Laminar simulation with Simple Algorithms and Coupled Algorithms.

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Old   April 26, 2013, 18:46
Question Laminar simulation with Simple Algorithms and Coupled Algorithms.
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Yanming LIU
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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.
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Old   April 30, 2013, 09:55
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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?

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Old   April 30, 2013, 10:54
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Are there some turbulent transition model in Fluent? What's your meaning of Low Re model? Thanks for your answer.
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Old   April 30, 2013, 11:02
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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.
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Old   April 30, 2013, 11:15
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Thanks. I will try them right now.
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