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-   -   Rotor 37 problem (http://www.cfd-online.com/Forums/openfoam-solving/125706-rotor-37-problem.html)

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,

Thanks for your reply
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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