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How to visualize Wakes in simulations

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Old   October 13, 2019, 06:06
Default How to visualize Wakes in simulations
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chandra shekhar pant
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Dear Foamers,


I have done a bunch of simulations using openfoam for flow over a 3-D blade and kind of propellor simulations. I am not sure how to see and visualize the wake ?
Some doubts:
1. Is plotting vorticity same as that of wakes
2. What should be the color scale of the vorticity

3. If I am not able to see the wakes/vorticity then the simulations/grid is wrong
4. If vorticity is same as that of wake. How to plot it?


Many questions may not make sense, sorry for that.


Many thanks!
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Old   October 14, 2019, 05:44
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Kmeti Rao
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Quick answer,

To visualize the flow in the wake or upstream, use Q criteria, which can be executed using 'postProcess -func Q'
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Old   October 14, 2019, 06:12
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Carlo_P
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Hey Chandra,
in OpenFOAM you can use the Q-criterion.
You have to run solver -postProcess -func Q -latestTime -
Then in paraview you can create a threshold.
The value above with consider the wale is not the same for each simulation, you have to play a little on it.
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Old   October 14, 2019, 08:18
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Many thanks Kmeti Rao and Carlo for your help. Before writing this post/thread I already tried to use -func vorticity and -func Q etc but could not achieve the desired result. Just thinking may be the simulations/grid is not correct. I am not sure how to put this problem now.


Thanks again!
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Old   October 15, 2019, 02:42
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Kmeti Rao
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Hi Chandra Shekar,

did you check it with different values of Q as Carlo mentioned?

Quote:
Then in paraview you can create a threshold.
The value above with consider the wake is not the same for each simulation, you have to play a little on it.
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Old   October 15, 2019, 08:55
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chandra shekhar pant
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Sincerely speaking I don't understand that.
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Old   October 15, 2019, 09:34
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Which part didn't you understand?


After simulation,you run simpleFoam -postProcess Q
then

paraFoam
then create a threshold
then put as minimum 0.5 or other values.
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Old   October 15, 2019, 10:13
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chandra shekhar pant
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Hello Carlo,



I am extremely thankful for your patience and help. Sorry for being naive, I am actually looking the wakes around a propeller and to see that firstly I make a slice of the propeller and then select the internal mesh, and then visualize the velocity etc. I don't know if this makes sense or not.

By the way I think by threshold you mean Threshold filter in which max and min values are there? Again Sorry.


Thanks a lot for your time and kind patience.
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