[highhopes]

Dear respected members of the CFD community,

Recently I attended a talk about computational investigation of a viscous flow in a conduit. The speaker said they had to switch to turbulence modeling because the flow "became" turbulent around a turn. I asked them how they came to the conclusion that there was a transition and they said it was a computational finding. I could not ask any further because of time constraints but I had to take the answer with a pinch of salt because the decision sounded a little too casual to me.

Here I would like to ask you if there is actually a way of deciding whether a laminar flow gets turbulent anywhere downstream? I would love to hear your thoughts on this.

Thank you.

[LuckyTran]

I highly doubt it was purely a computational finding. I'll believe that when I see it. If that work was performed, it'd be groundbreaking.

I will accept that they used some other practical judgement such as checking the duct Reynolds number and finding out that it was greater than 2300, or something of this level of simplicity.

Even DNS doesn't magically yield that a pipe flow is turbulent at Re=2350, we have to resort to stochastic methods to get this result.

[FMDenaro]

Originally Posted by highhopes

Dear respected members of the CFD community,

Recently I attended a talk about computational investigation of a viscous flow in a conduit. The speaker said they had to switch to turbulence modeling because the flow "became" turbulent around a turn. I asked them how they came to the conclusion that there was a transition and they said it was a computational finding. I could not ask any further because of time constraints but I had to take the answer with a pinch of salt because the decision sounded a little too casual to me.

Here I would like to ask you if there is actually a way of deciding whether a laminar flow gets turbulent anywhere downstream? I would love to hear your thoughts on this.

Thank you.

Generally, what you are asking for is the capability of CFD in simulating a transitional flow, that is a condition in which laminar, transitional and turbulent regime coexist.

This kind of problem can be afforded only with a DNS formulation, LES with a wall resolved grid and a good SGS model could be also a good candidate.

[highhopes]

Thank you very much for your answers. I had also figured this sort of simulation would be close to impossible considering the low computational resources.
Also thank you very much letting me know that, even expensive, there are ways to locate transition from laminar to turbulent flow via computations.