# Turbulence model for lower Reynolds number in transient analysis

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 October 25, 2017, 06:14 Turbulence model for lower Reynolds number in transient analysis #1 Member   Dr Gurubasavaraju Join Date: Dec 2014 Location: Bengaluru India Posts: 77 Rep Power: 11 Hi all, Could anyone please help me understand below questions. 1. How to choose turbulence models for laminar, transient analysis? 2. Which is best turbulence model for Reynolds number of around 200 (two hundred)? 3. Is SST compatible for Reynolds number of less than 500? 4. What are the consequences if we use turbulence model for lower Reynolds number.

 October 25, 2017, 07:27 #2 Senior Member   Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 13 Why would you use a turbulence model for a laminar flow type? Is your problem truely laminar as your Reynolds number might implicate? lcarasik likes this.

 October 25, 2017, 07:29 #3 Member   Dr Gurubasavaraju Join Date: Dec 2014 Location: Bengaluru India Posts: 77 Rep Power: 11 Sorry, It supposed to be Unsteady, transient flow.

 October 25, 2017, 07:41 #4 Senior Member   Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 13 Is it single or multiphase? Can you describe what you want to model/simulate? From your Reynolds number alone i would suggest to simulate without any turbulence model.

October 25, 2017, 08:14
#5
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Dr Gurubasavaraju
Join Date: Dec 2014
Location: Bengaluru India
Posts: 77
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Not exactly a multiphase flow. But one portion region is non-newtonain and other is Newtonian (see attachment).
The simulation is on the flow of magnetorheological fluid in a damper. The flow of fluid is due to the motion of the piston head.
fluid flow inside the damper will be random.
Attached Images
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 October 25, 2017, 08:38 #6 Senior Member   Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 13 SST k-omega is usually i good choice, but check the requirements.

 October 25, 2017, 08:43 #7 Member   Dr Gurubasavaraju Join Date: Dec 2014 Location: Bengaluru India Posts: 77 Rep Power: 11 yea, I just wanted to understand, whether the turbulence model can be used only based on the Reynolds number or some other factors are also need to be considered while choosing.

October 25, 2017, 10:18
#8
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Filippo Maria Denaro
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Quote:
 Originally Posted by gbrajtm yea, I just wanted to understand, whether the turbulence model can be used only based on the Reynolds number or some other factors are also need to be considered while choosing.
You have to consider the physics of your problem and the Reynolds number can give only some information. Depending on the velocity and lenght scales used in defining the Re number, you can have turbulence at low Re number (Re_tau=180 was a well known test for turbulence in channel flow) while you can have laminar condition along a flat plate at higher Re_x numbers.

 October 25, 2017, 11:34 #9 Member   Dr Gurubasavaraju Join Date: Dec 2014 Location: Bengaluru India Posts: 77 Rep Power: 11 Thank you very much.

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