CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   SU2 (http://www.cfd-online.com/Forums/su2/)
-   -   What are the variables "conservative_"? (http://www.cfd-online.com/Forums/su2/125949-what-variables-conservative_.html)

shsreekanth November 5, 2013 02:41

What are the variables "conservative_"?
 
Hi,
I am using SU2 V2.0.7
1.When the result of turbulent flow over flat plate is opened in ParaView, I see that there are variables "conservative_1","conservative_2"...."conservative _5". What are these variables?
2.Where is velocity? This used to be there with SU2 V2.0.0
3.Which one is density?

Sreekanth

economon November 5, 2013 19:57

Hi Sreekanth,

The conservative variables for the governing flow equations (Euler, N-S, RANS) are the mass, momentum, and energy, i.e. U = ( density, density*velocity, density*energy)^T. Therefore, the density is the first conservative variable, and in order to get the velocity, you should divide the momentum components by the density. In 2-D, for example, the x-velocity would then be vel_x = Conservative_2/Conservative_1.

Cheers,
Tom

shsreekanth December 19, 2013 14:10

Conservatives
 
Hi,
Based on the above explanation , I would have 4 conservatives for a 2D problem and 5 for 3D problem.
I did a 2D problem in SU2 with Physical_problem = Navier stokes and KIND_TURB_MODEL= SA
I get 5 conservative variables .
If its a 3D problem, I get 6 conservatives. Which is the extra conservative variable calculated?

liujmljm December 19, 2013 17:15

Quote:

Originally Posted by shsreekanth (Post 467089)
Hi,
Based on the above explanation , I would have 4 conservatives for a 2D problem and 5 for 3D problem.
I did a 2D problem in SU2 with Physical_problem = Navier stokes and KIND_TURB_MODEL= SA
I get 5 conservative variables .
If its a 3D problem, I get 6 conservatives. Which is the extra conservative variable calculated?

Dear, I suggest u should read some books on Fluid dynamics or CFD.
The extra conservative variable is eddy-viscosity variable in SA turbulent model.

Merry Xmas and happy new year.

Good Luck

shsreekanth December 20, 2013 04:08

Thanks
Merry X'mas and Happy new year

Nielson2 February 23, 2014 15:03

Missing functionabilities?
 
Hi all,

I would like to continue this thread, if I may, with a question with regard to the conservation variables.

Sreekanth mentioned that the velocity parameter has disappeared in version 3.0, while it was there in the second version. I noticed the same, which I found quite a shame. The transition also changed the output parameters of flow.vtk files. With v2.0 flow.vtk files, I was able to visualize the direction of flow or velocity with the usage of glyphs in Paraview. I haven't found a way to achieve the same with v3.0 flow.vtk files. Does anybody know how I can achieve this?

Moreover, the v3.0 flow.vtk files also seem to miss the streamline functionability in Paraview.

Do I have to convert the flow.vtk files to be able to use this functions? If yes, how can I do this?

Thanks in advance!

Niels

shsreekanth February 24, 2014 02:30

Hi,

To get the velocity vector , you have to use the filter 'calculator' in paraview. For 3D, the new variable should be "conservative2"/"conservative1"*iHat+"conservative3"/"conservative1"*jHat + "conservative4"/"conservative1"*kHat. This will give velocity vector (u,v,w) . After that, you can apply streamlines

I hope this is what you asked about.

Sreekanth

JinZhiyi February 24, 2014 13:01

Quote:

Originally Posted by liujmljm (Post 467101)
dear, i suggest u should read some books on fluid dynamics or cfd.
The extra conservative variable is eddy-viscosity variable in sa turbulent model.

Merry xmas and happy new year.

Good luck

大哥您可是真犀利```

Nielson2 February 24, 2014 15:16

Quote:

Originally Posted by shsreekanth (Post 476409)
Hi,

To get the velocity vector , you have to use the filter 'calculator' in paraview. For 3D, the new variable should be "conservative2"/"conservative1"*iHat+"conservative3"/"conservative1"*jHat + "conservative4"/"conservative1"*kHat. This will give velocity vector (u,v,w) . After that, you can apply streamlines

I hope this is what you asked about.

Sreekanth

Thanks! That was indeed what I was looking for!

shsreekanth February 24, 2014 16:05

Hi,

Also, all these variables are scaled. So to get the actual value of velocity, you must multiply it with the value of reference velocity.


All times are GMT -4. The time now is 07:08.