How to visualize Wakes in simulations

chandra shekhar pant · October 13, 2019, 06:06

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!

Krao · October 14, 2019, 05:44

Quick answer,

To visualize the flow in the wake or upstream, use Q criteria, which can be executed using 'postProcess -func Q'

Carlo_P · October 14, 2019, 06:12

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.

chandra shekhar pant · October 14, 2019, 08:18

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!

Krao · October 15, 2019, 02:42

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.

chandra shekhar pant · October 15, 2019, 08:55

Sincerely speaking I don't understand that.

Carlo_P · October 15, 2019, 09:34

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.

chandra shekhar pant · October 15, 2019, 10:13

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.

October 13, 2019, 06:06	How to visualize Wakes in simulations	#1
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 17	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!

October 15, 2019, 09:34		#7
Carlo_P Senior Member Carlo_P Join Date: May 2019 Location: Italy Posts: 176 Rep Power: 8	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. chandra shekhar pant likes this.

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October 14, 2019, 05:44		#2
Krao Senior Member Kmeti Rao Join Date: May 2019 Posts: 145 Rep Power: 8	Quick answer, To visualize the flow in the wake or upstream, use Q criteria, which can be executed using 'postProcess -func Q'

October 14, 2019, 06:12		#3
Carlo_P Senior Member Carlo_P Join Date: May 2019 Location: Italy Posts: 176 Rep Power: 8	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.

October 14, 2019, 08:18		#4
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 17	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!

October 15, 2019, 08:55		#6
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 17	Sincerely speaking I don't understand that.

October 15, 2019, 10:13		#8
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 17	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.