Some problems are fully laminar and the other initiate as laminar and establish as turbulent flow. Other problems are turbulent with lower Reynolds number than Critical Reynolds number such as corrugated surface. so , How can i select between laminar and turbulent viscous model based on flow type although it may convert from laminar to turbulent or may be turbulent with low Reynolds number than Critical Reynolds number.
if the possibilities is their than divide in to parts
steady and unsteady analysis of our work
Dear Alatyar,
Generally, in broader terms the single phase fluid flow can be divided in to two parts namely, external flow and internal flow. Based on this the flow properties like Reynolds number can be calculate. For an example, if you willing to investigate the flow across the bluff bodies which is basically the external flow so for this case you calculate the Re and based on that laminar and turbulent case consider. On the other side if you willing to find the transition region then its a classical research problem you may choose any specific geometry and conduct experimental investigation. Besides, I also suggest to read some basic books & article related to external & internal flow and transition.
Regards
Mr. Shukla
In FLUENT, when I select Laminar viscous model , the governing equation of momentum conservation will be in the terms of laminar viscosity.While selecting Turbulent viscous model, the governing equation of momentum conservation will be in the terms of turbulent viscosity in addition to the selecting turbulent model (for example K-epsilon model) conservation of turbulence kinetic energy and energy dissipation will be considered.
So if the problem is laminar and I select laminar viscous model , the momentum conservation equation will be right.
and if the problem is turbulent and I select turbulent viscous model , the momentum conservation equation will be right in turbulent region only while in laminar region this equation will be wrong.
finally I accept with you at the third type problem (problems are turbulent with lower Reynolds number than Critical Reynolds number such as corrugated surface) as I should conduct experimental investigation to know the critical Reynolds number and hence the flow type; laminar or turbulent.
Do I specify the two different zones by selecting "laminar zone" in "cell zone condition" and selecting the "turbulence model" in "viscous model" selection.
Are you investigate the conversion of flow from laminar to turbulent in a channel or something like this ? I suggest could you specify some more details about your problem as it need to justify properly. However, as per understanding from your question if Re number is same throughout the domain then you need not to define two different cell zone i.e the flow is laminar or turbulent depend on the Re based on that you chose flow condition.
I hadn't reached to any thing with "laminar zone" (divergent solution ) as I modeled a flow over flat plate (as an example)
FLUENT solver has a two transition model ; transition SST model and transition k-kl-omega model, Nearly that is what i want.
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