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 S.N.Paul October 29, 2013 13:31

Rotor 37 problem

Hello,

I am doing a rotor 37 simulation of a single blade passage with periodic BC using openfoam 2.2, i am not able to figure out which solver to use. Currently i m using rhoPorousMRFSimpleFoam.
I am not able to get any results, negligible flow is going inside the main domain .Can anyone guide me how to do this. I read somewhere that you have to develop a compressor map by changing the back pressure. How to do that ??

rpm of rotor is = 12465
My boundary conditions are:
-------------------------------------------------------------------------
p

Code:

```dimensions      [ 1 -1 -2 0 0 0 0 ]; internalField  uniform  349300; boundaryField {     Blade     {         type            zeroGradient;     }     Inlet     {                      type            totalPressure;       p0              uniform 342000;           value          uniform  349300;         U              U;         phi            phi;         gamma          1.40;         rho            rho;         psi            none;     }     Outlet     {       type                fixedValue;       value              uniform  349300;     }     Shroud     {         type          zeroGradient;     }     Hub     {         type          zeroGradient;     }   periodic_upper     {         type            cyclic;     }     periodic_lower     {         type            cyclic;     } }```
--------------------------------------------------------------------------
U
Code:

```dimensions      [ 0 1 -1 0 0 0 0 ]; internalField  uniform (1 1 0); boundaryField {     Blade     {         type            fixedValue;         value          uniform (0 0 0);     }     Inlet     {       type            pressureDirectedInletVelocity;       inletDirection  uniform (0.9975 0.0704 0);       value          uniform (0 0 0);     }     Outlet     {         type            inletOutlet;         inletValue      \$internalField;         value          \$internalField;     }     Shroud     {         type            fixedValue;         value          uniform (0 0 0);     }     Hub     {         type          fixedValue;         value          uniform (0 0 0);     }   periodic_upper     {         type            cyclic;     }     periodic_lower     {         type            cyclic;     } }```
-------------------------------------------------------------------------
T
Code:

```dimensions      [ 0 0 0 1 0 0 0 ]; internalField  uniform 482.94; boundaryField {     Blade     {         type            zeroGradient;     }     Inlet     {         type            totalTemperature;         T0              uniform 500.5;         value          uniform 500.5;         gamma          1.4;         phi            phi;         psi            thermo:psi;     }     Outlet     {         type            zeroGradient;     }       Shroud     {         type            zeroGradient;     }     Hub     {         type          zeroGradient;     }   periodic_upper     {         type            cyclic;     }     periodic_lower     {         type            cyclic;     } }```
--------------------------------------------------------------------------

Thanks a lot !!

 wyldckat November 1, 2013 20:08

Greetings Paul and welcome to the forum!

I've gotten the private message you sent me.
Quote:
 Originally Posted by S.N.Paul (Post 459698) I am doing a rotor 37 simulation of a single blade passage with periodic BC using openfoam 2.2, i am not able to figure out which solver to use. Currently i m using rhoPorousMRFSimpleFoam.
I have no clue what a "rotor 37" is. Do you have any good online links on this topic?

Quote:
 Originally Posted by S.N.Paul (Post 459698) I am not able to get any results, negligible flow is going inside the main domain .Can anyone guide me how to do this. I read somewhere that you have to develop a compressor map by changing the back pressure. How to do that ??
Honestly, I think you're trying to solve waaaay too many problems in a single step.
My advice: step back and take a simpler look into the problem you're trying to solve. In other words: use the strategy to divide and conquer.

So, the basic questions are:
1. In essence, what exactly are you trying to simulate? I ask this from a point of view of ignoring all of the specific details.
2. What results to you need to extract from the simulation?
Best regards,
Bruno

 S.N.Paul November 2, 2013 14:07

Hello Bruno,

The NASA rotor 37 is an isolated transonic axial compressor rotor with 36 blades.
So instead of the whole rotor, i am simulating a single blade with periodic boundary conditions. So my domain consists of (inlet, outlet, hub shroud and a single blade)

I have the results from some other software, i just want to validate them using openfoam using the same BC.
So now any suggestions !!

 wyldckat November 2, 2013 16:36

Hi Paul,

:eek: Transonic? That's a big jump, at least for me, given my level of experience on this.

The best I can do is to suggest the following (and since you're using OpenFOAM 2.2):
1. The tutorial "incompressible/SRFSimpleFoam/mixer" has got a very simple geometry, with a 1/4th part of a mixer. It's designed for SRF, but it can be easily be modified to MRF and it's 3D.
2. Then there is is the tutorial "incompressible/simpleFoam/mixerVessel2D", which exemplifies how to set-up an MRF case, but it's 2D.
3. As for a solver, there are a few options that come to mind, but these are somewhat basic:
• rhoPimpleFoam
• rhoCentralFoam
• sonicFoam
A description for each one is given here: http://www.openfoam.com/features/standard-solvers.php
In theory, it shouldn't be necessary to use a solver whose name has got MRF in its name, but I'm not certain if all of them are "fvOptions" ready :(
4. As for your boundary conditions, now I'm getting a clearer picture:
1. The U field seems to have a wrong BC for it. It should be something like this:
Code:

```    outlet     {         type            inletOutlet;         inletValue      uniform (0 0 0);         value          uniform (0 0 0);     }```
2. The pressure BC... I have no idea if the "waveTransmissive" BC should or should not be used on the outlet. You can find out some more information about each boundary condition from here: http://www.openfoam.org/docs/cpp/
Beyond this, I can only hope that someone more experienced on this can answer.

Best regards,
Bruno

 Mahdi2010 November 26, 2013 06:44

I think you might finally end up with "sonicFoam" because NASA rotor 37
is a transonic rotor and you need to consider compressibility and turbulence for that. "sonicFoam" provides these issues for you, however you need to make a decision whether you should have mesh motion or not. in this case "sonicDyMFoam" could be a try.

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