|March 14, 2011, 03:14||
Conceptual doubt about laminar/turbulent flows
Join Date: Mar 2010
Location: Bangalore, India
Posts: 136Rep Power: 8
I have a very basic conceptual doubt about how we runa laminar or turbulent simulations.
1. Is there a definite way by which we can say a flow is laminar/turbulent or in transition ? Is it not dependent heavily on the geometry shape and it is more difficult to define weather a flow is laminar or turbulent for bodies with complicated geometry (like flow over a terrain or flow over an oil rig where there is no single fixed reference length).
2. If we know for sure that a flow is laminar but we run it as a turbulent simulation, will not the artificial numerical turbulence die on it's own ?
In other words what are the pits falls of our choice.
Thanks in advance to anyone who enlighten me with these doubts.
|March 16, 2011, 06:25||
Join Date: Feb 2011
Posts: 5Rep Power: 7
I have the same question with you and I would like to just present my own thinking,
(1). Generally in macroscale, the difference between laminar and turbulence flow is Re around 2300. But during CFD analysis, we usually encounter problems with various Re or special geometries where no Re could be calculated. At this time i tend to use turbulence.
(2). I was told by someone that using turbulence model in a laminar flow problem only increases the calculation time. Yes there are much possibilities of numerical diffussion, but as long as the result converge..
Of couse, we should test with calculating both models in the same boundary.
|March 16, 2011, 10:19||
how to create turbulent flow
Join Date: Sep 2010
Posts: 3Rep Power: 8
i'm new to cfd..therefore,i'm having a problem to define the variable to run turbulent flow..
it is very appreciate to those can help me with this..
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