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J October 27, 2008 10:20

Velocity plot
Hello people! Listen up...I have a problem...consider the case of a flow in a tube, and consider a core flow with a reversal flow near the boundaries of the tube. I would like to plot this situation...if I do the vector plot honestly sucks (especially if you use this in a publication), so what I want to do is a contour plot. If I take "velocity" as variable CFX, I think, is plotting the magnitude so no way of seeing the reversal...if I plot just one component, like z-component of the velocity I should see some flow with positive velocity and some flow with negative velocity...but is not working...seems to be that CFX is cutting the negative velocity putting 0. Have you any idea on how to solve this problem?

Thanks in advance


LKF October 27, 2008 11:20

Re: Velocity plot
Try switching between Hybrid and Conservative values. It may solve your problem?

J October 27, 2008 11:42

Re: Velocity plot
I tried but didn't help since this feature is just to adjust the value near the boundaries. Consider that in my case the negative velocity has to be negative in the middle of the duct, not near the boundaries... But thanks for your help ;) J

CycLone October 27, 2008 11:48

Re: Velocity plot
Post should not clip the negative values, unless you have specified a range for your contour plot manually. If you are plotting the velocity component (Velocity u, Velocity v, Velocity w), it can go negative. However, as you have pointed out, the velocity magnitude (Velocity) is always positive.

Check your range. Set it to local or manually specify the contour range to ensure you negative velocities are plotted.


J October 27, 2008 11:57

Re: Velocity plot
Thanks! I'll try that and I'll let you know. Thanks again for your help. J

LKF October 27, 2008 13:13

Re: Velocity plot
Your original post defined "a core flow with a reversal flow near the boundaries of the tube" which is why I suggested the Hybrid/Conservative values. I assumed your negative Vel w values were near the wall.

Good luck.

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