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Meaningul drag output

Posted 23 janv. 2011, 17:02 UTC−5 Computational Fluid Dynamics (CFD), Studies & Solvers Version 4.2 1 Reply

Alex Lovallo
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This is a working stationary turbulent flow model.

I have created an integral solution set around the boundaries of the object id like to determine lift and drag for.

All posts i have read involve using -reacf(v) and -reacf(u) but these only return 0s for me.
In addition there is no preset drag selection as an expression as there was for laminar flow.

What I would like to do is compare a few shapes and select the one with the least drag and most lift. Can someone advise me on how to do this please? Once this model is working I will put the different geometries into it.

The model is attached

thanks so much!

Alex
1 Reply Last Post 13 déc. 2012, 22:09 UTC−5
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Hello Alex Lovallo

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Jeramy Stewart
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Posted: 1 decade ago 13 déc. 2012, 22:09 UTC−5
I have the same problem. I would like to determine the drag coefficient on a cylinder for higher reynolds numbers. I have basically just used the flow over a cylinder model and I am trying to get the drag coefficient for reynolds numbers going from 1 to 10,000,000. when I tried to solve it for Reynolds = 1000 (U_mean=0.02) I got an error and when I tried the turbulence model with Reynolds =1000 I got a drag coefficient of about 0. I bumped up the reynolds number (by increasing the velocity) to be sure that I am clearly in the turbulence range and I can only get drag coef of 0. I am using reacf(u) to get my drag (which has been working for the lower reynolds numbers), but I can not get anything other than drag coefficient of 0 for turbulent flow model.
I have the same problem. I would like to determine the drag coefficient on a cylinder for higher reynolds numbers. I have basically just used the flow over a cylinder model and I am trying to get the drag coefficient for reynolds numbers going from 1 to 10,000,000. when I tried to solve it for Reynolds = 1000 (U_mean=0.02) I got an error and when I tried the turbulence model with Reynolds =1000 I got a drag coefficient of about 0. I bumped up the reynolds number (by increasing the velocity) to be sure that I am clearly in the turbulence range and I can only get drag coef of 0. I am using reacf(u) to get my drag (which has been working for the lower reynolds numbers), but I can not get anything other than drag coefficient of 0 for turbulent flow model.

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