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-   -   Can RMS velocity even be smaller than mean velocity? (http://www.cfd-online.com/Forums/fluent/102123-can-rms-velocity-even-smaller-than-mean-velocity.html)

lgas222 May 22, 2012 22:57

Can RMS velocity even be smaller than mean velocity?
 
Dear all,

I'm using the mixture, k-e, air-water two phases model in FLUENT to simulate bubble column. I calculated with transient mode.

After calculation, I checked the results: RMS velocity magnitude and mean velocity magnitude. I found out that RMS value is even smaller than mean value. Does anyone know how can it be like this? Is there anything wrong?

Thanks a lot.

Far May 23, 2012 01:17

It can be. RMS is the root mean square of fluctuating components that is u',v' and w'.

lgas222 May 23, 2012 04:18

Quote:

Originally Posted by Far (Post 362585)
It can be. RMS is the root mean square of fluctuating components that is u',v' and w'.

Thanks for your reply.

I have one more question: is RMS calculated as ((x1^2+x2^2+x3^2+...+xn^2)/n)^0.5?

Far May 23, 2012 04:26

I guess so.

Far May 23, 2012 04:36

Some links are shared here, where you can find the discussion about the RMS velocity
http://www.cfd-online.com/Forums/flu...ity-ratio.html


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