[brownmj]

Hello foamers!

I am running a single propeller blade using SRFSimpleFoam and periodic boundary conditions (cyclicAMI). My question has to do with the initial conditions of the flow. As far as I can tell, the only way to specify the initial conditions (for velocity, that is) is in the 0/Urel file, where all the velocities are, of course, relative.

For my inlet, far-field boundaries, I can use type=SRFVelocity and set relative=no in order to specify a uniform axial velocity (in the absolute reference frame). HOWEVER, I cannot figure out a way to input a uniform axial velocity in the absolute reference frame for the internalField. All I can do is set the RELATIVE velocity to (1 0 0), meaning that the initial condition for the flow is to be rotating with the propeller blade.

So, of course I'm having problems getting a converged solution and I think it could be because my initial condition is so far off from the physical solution.

Does anyone have any tips on how to input an initial condition of uniform velocity in the absolute frame to SRFSimplefoam?

In the meanwhile, I am running a case with very low RE# (~300). Hopefully all the extra viscosity will help the inlet and farfield BC's to decelerate all that rotating flow, and then I can update the RE# to a higher one once I get convergence. Any thoughts on this plan?

I've included my Urel file below, thanks for reading!

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                               |
|   \\  /    A nd           | Web:      http://www.OpenFOAM.org               |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      Urel.orig;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions      [0 1 -1 0 0 0 0];
internalField  uniform (1 0 0);
boundaryField
{
    hub-6
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    farfield-5
    {
        type            SRFVelocity;
        inletValue      uniform (1 0 0);
        relative        no;
        value           uniform (1 0 0);
    }
    blade-4
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    periodic_sfc1-9
    {
        type            cyclicAMI;
    }
    periodic_sfc2-10
    {
        type            cyclicAMI;
    }
    outlet-8
    {
        type            zeroGradient;
    }
    inlet-7
    {
        type            SRFVelocity;
        inletValue     uniform (1 0 0);
        relative        no;
        value           uniform (1 0 0);
    }
}
 
// ************************************************************************* //

[brownmj]

Hi guys,

I just wanted to report back that I have fixed my own issue. Running 4000 times steps at a high viscosity was enough to get a somewhat converged solution. I then changed back to the desired viscosity and ran another 2000. Now, the forces are looking good compared to the experiment.

A colleague also has been teaching me about SwAK4Foam, and we have been trying to get those codes compiled on my machine so that I can use them to set up better initial conditions. However, as of Friday 3/1/14, the SWAK source doesn't seem to be compatible with OF 2.3.0.

[oldirtybrindley]

I am trying to simulate a Hydro-kinetic turbine blade. Could you share your case directory with me?

[Jiricbeng]

Hi brownmj,
would you mind uploading your files? I am struggling with similar issue.

[ashim]

Hi,

Good morning. I am trying to simulate the same case as Mike, one propeller blade with cyclic boundary at the two sides using SRFSimpleFoam. After few iterations the time step continuity error become high and stops the simulation with error message. I couldn't understand the reason behind it. I am trying solve it from the last two weeks. But no progress. I think I have messed up the boundary conditions and solver settings. Would you please help me providing hints / advice. Any kind of help is appreciated.

Ali

[kiddmax]

Hi Ali,

I have the same problem. Did you solve your issue?

Best regards
Ye

[ashim]

Hi Ye,

Still now, I couldn't solve the problem. I have figured out that pressure at some points is relatively high than others. The pressure calculation is not going in correct way. I am expecting some help from this forum. Can anyone please help me?

Best regards,

Ali

[kiddmax]

Hi Ali,

Thank you for your reply. I searched similar thread about SRFSimpleFoam, and what I conclude is that this solver maybe is not stable as MRFSimpleFoam. So I want to try MRFSimpleFoam and see what happens.

Kind regards,
Ye

[chakshu]

Hi Guys,


I know it has been a while on this post but any solution for the same problem? I am struggling with same issues, any kind of input is most welcomed.


I am trying to simulate a UAV propeller.


Thanks.
Regards.