CFD Online Discussion Forums - Drag Coefficient Verification around Cylinder

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Please give more of the setup details, e.g., Reynolds number, turbulence model (if any), etc.

Hi Glenn,

Yes, I am checking it now with 1000 time-steps/cycle.
I have previously used 100 and 200 time-steps/cycle.

My model is 2d with an added one-element thickness in z-direction.
Axially, it covers a distance of 3c (from inlet to object) to 8c (from object to outlet). Laterally, 7c to upper and lower boundary.
The total element now is around 200,000.
I will increase it further.

Cheers,
bbhv

Sounds like your domain might be too small. 3c from the inlet is pretty small, especially considering the high-pressure front surface that blunt object causes.

Try increasing your domain in every direction and creating a coarse mesh in the extended regions so that the simulation is not significantly longer.

Quote:

Originally Posted by MFerris
;88669

I am trying to do a basic verification of drag coefficient around several basic shapes starting with a simple cylinder. I'm using the force values calculated in CFX to calculate the coefficient of drag. The Cd is quite low compared to data from various text. Yplus values are well below 1. Domain is very large compared to cylinder. I've simulated over several Reynold's numbers (Cd varies with Re). I've been working with ANSYS/CFX tech support for several days and they're scratching their heads as well. Has anyone performed a simple verification of external flow around a cylinder with satisfactory results? Cd should be around 1.2 for Re of 10^3 to 10^5. I get around .65 along with the ANSYS support folks.

Hi,

I have the same problem. I get Cd=0.5 but exp value is 1.2 for 2D cylinder.

What should i do?

thanks