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-   -   test case for navier stokes (http://www.cfd-online.com/Forums/main/97475-test-case-navier-stokes.html)

panou February 17, 2012 17:26

test case for navier stokes
 
Could you tell me which test cases with analytical solution exist for validation or verification of navier-stokes equations (compressible flow)?
Also, where will i found the complete setup of them?

I know the laminar boundary layer, but due to large computational cost i want another case.

Thanks

leflix February 22, 2012 17:25

Quote:

Originally Posted by panou (Post 345013)
Could you tell me which test cases with analytical solution exist for validation or verification of navier-stokes equations (compressible flow)?

Thanks

Up to my knowledge there is no analytical solution of compressible NS equations, but try this: http://www.springerlink.com/content/khk855n125555p7r/

for incompressible flow you have several analytical solutions in 2D
Poiseuille, couette

cfdnewbie February 23, 2012 05:09

If you have access to the code and could add a source term, there's an infinite number of analytical solutions for the NS equation with source term.... as far as I know, that's the only method to validate and verifiy your code thoroughly.

leflix February 23, 2012 06:31

Quote:

Originally Posted by cfdnewbie (Post 345869)
If you have access to the code and could add a source term, there's an infinite number of analytical solutions for the NS equation with source term.... as far as I know, that's the only method to validate and verifiy your code thoroughly.

Hi cfdnewbie,

An analytical solution for compressible NS equations means you have the functions:

u(x,y,z,t)
v(x,y,z,t)
w(x,y,z,t)
p(x,y,z,t)
ro(x,y,z,t)
T(x,y,z,t)

for any x,y,z, and time t.

as far as I know it only exists in incompressible 2D poiseuille and couette flows.
There is also a 3D incompresible transcient solution.

But for sure there is not an infinite number of such solution as you say especially in compressible.
If we were able to determine analytical solution of compressible NS equations CFD would certainly not exist any longer !!!

If you have these 6 functions for any x,y,z,t then the nobel price is for you my friend !!!!

leflix February 23, 2012 06:39

cfdnewbie have you heard about the 7 problems of the millenium proposed by Clay Mathematical Institute?
The analytical solution of Navier-Stokes equations is the 6th of them !!
So if you are able to produce such solution you will also earn 1 million dollars
+ 1 million dollars of nobel price..
so go ahead you will be rich ;)

niaz February 23, 2012 08:06

why you don't choose experimental test cases?

agd February 23, 2012 10:40

cfdnewbie is referring (I believe) to the method of manufactured solutions for validating the code. That may be your best approach for verifying your code.

cfdnewbie February 23, 2012 11:44

Quote:

Originally Posted by agd (Post 345943)
cfdnewbie is referring (I believe) to the method of manufactured solutions for validating the code. That may be your best approach for verifying your code.

Yes, thank you, I am indeed. It's the standard method used widely for code verification, and the emphasis is on Navier Stokes WITH source term, as mentioned in my first post. I wouldnt trust a code not verified that way with a rigorous test suite.

So no 1 mio for me, it's just what everybody else in code development is doing ( or should be doing)!

sbaffini February 24, 2012 17:08

By the way, the Clay prize is not for someone providing solutions to the N-S equations. It is for someone proving (or disproving) that the 3D incompressible form of the equations has a solution and that it is unique for given initial and boundary conditions + some conditions on the functional spaces all these functions belongs to.
Far more interesting...

FMDenaro February 25, 2012 18:25

Quote:

Originally Posted by sbaffini (Post 346196)
By the way, the Clay prize is not for someone providing solutions to the N-S equations. It is for someone proving (or disproving) that the 3D incompressible form of the equations has a solution and that it is unique for given initial and boundary conditions + some conditions on the functional spaces all these functions belongs to.
Far more interesting...

that's right, exact particular solutions of NS exist ...

as far the test-case for compressible flows is concerned, I can suggest to try the compressible Poiselle flow or some particular 1d cases:
http://www.waset.org/journals/waset/v43/v43-27.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/p010705.pdf


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