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-   -   Turbulence modelling in CFD (http://www.cfd-online.com/Forums/main/5108-turbulence-modelling-cfd.html)

Fabian September 2, 2002 21:13

Turbulence modelling in CFD
 
I am a final year undergraduate student at university, and am doing my thesis on the numerical modelling of a 2-Stroke Engine using CFD-ACE.

I have sucessfully modelled 3D laminar flow, and now am looking to model turbulent flow. The problem is that i don't have any values for K and D (epsilon), to input into the simulation.

I am seeking help from anyone who has even approximate values for K and D that i can use as a starting point for the turbulent modelling of this simulation.

Any help that could be offered would be greatly appreciated.

Cheers

vinod September 6, 2002 08:52

Re: Turbulence modelling in CFD
 
as far as i know the general practice to take K is 0.5* times the free stream kinetic energy. i.e 0.5* uinfty**2 but for D(epsilon) it can give some high value, say 30000 or so.


Tim September 10, 2002 10:12

Re: Turbulence modelling in CFD
 
For K & E value at inlet I use:

K = 1.5 * (I*Uin)^2

E = (k^1.5)/characteristic length

I is some turbulence intensity (varies from case to case) - try 0.05 for a start

Tim


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