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low drag coefficient

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Old   August 8, 2008, 00:42
Default low drag coefficient
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i am running a simulation of turbulent flow past a stationary cylinder and the calculated drag forces are lower than the expected values. Does anyone know some common reasons for this to occur?

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Old   August 8, 2008, 02:12
Default Re: low drag coefficient
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have u given the reference values proper and ve u selected all the surface for drag calculation? Which is the package u r usin?which turbulence modelr u usin?
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Old   August 10, 2008, 21:37
Default Re: low drag coefficient
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i am using a k-epsilon turbulence model and i have set the reference value, these are set from the inlet is that the correct approach? Unsure on what you meant by seleced all the surface for drag calculation as i am using a Re of 10000 surface roughness doesn't have any effect?

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Old   August 14, 2008, 00:53
Default Re: low drag coefficient
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At the inlet you have to impose the proper values for the Turbulence parameters.Calculate the Turbulent kinetic for the given inlet boundary condition and Impose the same. And dissipation rate should be imposed as zero at the inlet.

This gives a better CFD prediction for Drag.This has given drag values close to theoritical values for ship hull hydrodynamics.
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