Average velocity of two different planes

niqbal · April 19, 2010, 10:34

Hi Foam Users,
I have done some MD simulations in OpenFOAM.The simulation is of water flow in a nanoChannel. At the center of the channel I had taken a slice along the z-axis and draw a velocity profile along the vertical line (y-axis). The velocity profile is atomistic. I want to take a couple of slices and want to take the profile of average velocity at those planes. Is there some way to combine the the velocity profiles and take the average of these profiles in paraview directly? or is there any other suitable way to do it? I am attaching screen shots also. The velocity profiles are at the same vertical line but at two different slices along the z-axis. I want to have the average of these velocity profiles.
Thanks in Advance.

slice1.jpg

velocity_profile1.jpg

velocity_profile2.jpg

chegdan · October 22, 2010, 16:35

I'm curious about this one as well. I would like to either obtain and average velocity profile from many slices or over a whole 3d domain. Anyone do this before?

Tobi · December 20, 2010, 06:59

What do the same with my temperatur profil.

I just can average my Inlet and outlet with "patchAverage T inlet/outlet" but i want to get the average temperature in some other planes. I heard that it is possible to make that with paraview but i don 't know how this works and which filter i have to use.

Some ideas ?

misge98 · December 28, 2010, 01:14

I am trying to simulate twin screw pump by using ANSYS-FLUENT and I used dynamic mesh but I have a problem when I preview mesh motion and I got negative volume. before that I used ANSA for intial meshing of the model I think I have to smoothing the mesh but I couldn't, please can you suggest me how can I have to solve it and if you know any other refference on screw pump simulation please tell me.

Thank you!!!

Tobi · January 3, 2011, 15:02

I solved it.

You have to do the following steps:

1. open paraview
2. load your file or paraFoam etc.

3. set a slice and apply
4. use the filter -> integrateVariables and apply
5. use the filter -> calculator and apply
6. attribute mode: cell data
7. set a name and then use U/Area for average the velocity over that area ... T/Area for temperatur and so on and apply
8. activate integrateVariables and use "showing -> calculator" and change it to cell data.

The name "result" is the average velocity or so on... you can change the name "result" in the calculator...

thats it ...

bye tobi

shadabdyn · June 17, 2017, 16:12

Dear Tobi,

I have followed the above steps to calculate the average velocity on the slice but I have one confusion i.e by dividing the velocity by area the result will be of dimension [LT]^-1 which clearly is not the dimension of velocity but according to you the result is giving average velocity.
How is that possible?

Thanks & Regards
Shadab Mohammed

Tobi · June 19, 2017, 06:08

IntegrateVariable will multiply the quantity by the area or volume of the face/cell. Thats why you have to divide by the complete area/volume at the end again.
You can also make some simple tests to see that this holds or not. E.g. hotRoom tutorial -> uniform field (like T) at time = 0 - slice it, integrateVariable -> T gets 15000 K which could not be correct. Using caluclator filter and divide by the area lead to the average temperature of 300 K again (of course it is the new field).

Hope that it gets clear now. The evaluation should be like (for integrated values):
$\phi_A = \sum_i^n \phi_i A_i$
$\phi_V = \sum_i^n \phi_i V_i$

April 19, 2010, 10:34	Average velocity of two different planes	#1
niqbal New Member Naveed Iqbal Join Date: Oct 2009 Location: Germany Posts: 19 Rep Power: 16	Hi Foam Users, I have done some MD simulations in OpenFOAM.The simulation is of water flow in a nanoChannel. At the center of the channel I had taken a slice along the z-axis and draw a velocity profile along the vertical line (y-axis). The velocity profile is atomistic. I want to take a couple of slices and want to take the profile of average velocity at those planes. Is there some way to combine the the velocity profiles and take the average of these profiles in paraview directly? or is there any other suitable way to do it? I am attaching screen shots also. The velocity profiles are at the same vertical line but at two different slices along the z-axis. I want to have the average of these velocity profiles. Thanks in Advance. slice1.jpg velocity_profile1.jpg velocity_profile2.jpg

October 22, 2010, 16:35	average velocity profile in 3D space	#2
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	I'm curious about this one as well. I would like to either obtain and average velocity profile from many slices or over a whole 3d domain. Anyone do this before?

December 28, 2010, 01:14	hi friends	#4
misge98 New Member Abusha Join Date: Dec 2010 Posts: 2 Rep Power: 0	I am trying to simulate twin screw pump by using ANSYS-FLUENT and I used dynamic mesh but I have a problem when I preview mesh motion and I got negative volume. before that I used ANSA for intial meshing of the model I think I have to smoothing the mesh but I couldn't, please can you suggest me how can I have to solve it and if you know any other refference on screw pump simulation please tell me. Thank you!!!

January 3, 2011, 15:02		#5
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	I solved it. You have to do the following steps: 1. open paraview 2. load your file or paraFoam etc. 3. set a slice and apply 4. use the filter -> integrateVariables and apply 5. use the filter -> calculator and apply 6. attribute mode: cell data 7. set a name and then use U/Area for average the velocity over that area ... T/Area for temperatur and so on and apply 8. activate integrateVariables and use "showing -> calculator" and change it to cell data. The name "result" is the average velocity or so on... you can change the name "result" in the calculator... thats it ... bye tobi pavelow, indy07cz and shadabdyn like this.

June 19, 2017, 06:08		#7
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	IntegrateVariable will multiply the quantity by the area or volume of the face/cell. Thats why you have to divide by the complete area/volume at the end again. You can also make some simple tests to see that this holds or not. E.g. hotRoom tutorial -> uniform field (like T) at time = 0 - slice it, integrateVariable -> T gets 15000 K which could not be correct. Using caluclator filter and divide by the area lead to the average temperature of 300 K again (of course it is the new field). Hope that it gets clear now. The evaluation should be like (for integrated values): $\phi_A = \sum_i^n \phi_i A_i$ $\phi_V = \sum_i^n \phi_i V_i$ Shadab_Ilahi likes this. __________________ Keep foaming, Tobias Holzmann

December 20, 2010, 06:59		#3
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	What do the same with my temperatur profil. I just can average my Inlet and outlet with "patchAverage T inlet/outlet" but i want to get the average temperature in some other planes. I heard that it is possible to make that with paraview but i don 't know how this works and which filter i have to use. Some ideas ?

June 17, 2017, 16:12		#6
shadabdyn New Member shadab ilahi Join Date: Aug 2016 Posts: 11 Rep Power: 9	Dear Tobi, I have followed the above steps to calculate the average velocity on the slice but I have one confusion i.e by dividing the velocity by area the result will be of dimension [LT]^-1 which clearly is not the dimension of velocity but according to you the result is giving average velocity. How is that possible? Thanks & Regards Shadab Mohammed

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