[lienien]

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.

[oj.bulmer]

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

[lienien]

Are there some turbulent transition model in Fluent? What's your meaning of Low Re model? Thanks for your answer.

[blackmask]

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.

[lienien]

Thanks. I will try them right now.