CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Freesurface piercing foil numerical wiggles in gamma isosurface (http://www.cfd-online.com/Forums/openfoam-solving/59716-freesurface-piercing-foil-numerical-wiggles-gamma-isosurface.html)

egp April 7, 2007 10:15

Hi, I am running rasInterFo
 
Hi,

I am running rasInterFoam for a free-surface piercing NACA 0024 hydrofoil at Fr = 0.55. Overall, the solution looks quite good with nice resolution of the bow wave, the wave profile, and the spilling breaking wave.

So, what's the issue? I've run both coarse (~0.3M cells) and fine (~2M cells) hex meshes, and have some non-physical small amplitude waves in the gamma field which are seen on the gamma=0.5 iso-surface (i.e., the free surface).

Anyone have suggestions on fvSchemes settings to eliminate this problem? I am using standard rasInterFoam settings,

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default Euler;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
div(rho*phi,U) Gauss upwind;
div(phi,gamma) Gauss limitedLinear01 1;
div(phirb,gamma) Gauss limitedLinear01 1;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
interpolate(HbyA) linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
pd;
pcorr;
gamma;
}


// ************************************************** *********************** //

To get an idea of what I am seeing, I've put a couple of animations (naca0024...) for download at:

http://homepage.mac.com/egpaterson/FileSharing2.html

Thanks,

Eric

hjasak April 8, 2007 18:18

Try: div(phi,gamma) Gaus
 
Try:


div(phi,gamma) Gauss Gamma01 1;
div(phirb,gamma) Gauss Gamma01 1;


Hrv

egp April 9, 2007 19:02

Hrv, I tried the Gamma01 sc
 
Hrv,

I tried the Gamma01 scheme, although I did restart from the exisiting solution. However, it had no noticable impact.

We'll have to do some more digging to understand this better.

Eric

joakim April 11, 2007 03:13

Hi Eric I have had the same
 
Hi Eric

I have had the same problems using interFoam. The only way I have found to eliminate the overshoots is to use

div(rho*phi,U) Gauss upwind;
div(phi,gamma) Gauss upwind;


Regards

/Joakim

egp April 12, 2007 11:02

Hi Joakim, Thanks, as you c
 
Hi Joakim,

Thanks, as you can see from the image which compares upwind vs. limitedLinear01 on gamma http://www.cfd-online.com/OpenFOAM_D...ges/1/4182.jpg, the upwind scheme took care of the problem as would be expected with a first order scheme. However, it also smoothed the diverging wave in the wake. I'm going to test out the other TVD schemes.

Eric

egp April 12, 2007 11:17

Here's the 3D view http://www.
 
Here's the 3D view http://www.cfd-online.com/OpenFOAM_D...ges/1/4184.jpg.

Eric

carleykoko May 1, 2007 16:26

Hello, I am continuing to w
 
Hello,

I am continuing to work on this case. I would like to get a 2nd-order scheme working without the non-physical waves that were smoothed out by upwind.

Currently I am working with rasInterFoam, FR=0.55, coarse (~246,000 cell) grid. This is the same case Eric posted about above, all is the same except my fvSchemes dict which is below:


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default Euler;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
div(rho*phi,U) Gauss MUSCL;
div(phi,gamma) Gauss MUSCL;
div(phirb,gamma) Gauss MUSCL;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
interpolate(HbyA) MUSCL;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
pd;
pcorr;
gamma;
}


// ************************************************** *********************** //

Has anyone had any experience/problems implementing MUSCL?

I've run the following to attempt to get the solution started:
(1) water/air density ratio: 1000:100
CFL=0.1
ran OK for 75 time steps

(2) 1000:10
CFL=0.1
Did not work in that pcorr iterations were >5000 and/or deltaT was less than 1e-33 or CFL greater than 1.0

(3) changed to CFL=0.05, 0.04, 0.03
crashed in a similar manner

(4) changed the water/air density ratio to 1000:100 again and CFL=0.1: Runs OK!

(5) changed density ratio to 1000:50
CFL=0.1
runs OK

(6) changed density ratio to 1000:1
CFL=0.1, 0.05, 0.025, 0.0125, 0.00625
crashed as above

My next thought is to try ratio of 1000:10.

Any thoughts/comments/suggestions would be greatly appreciated.

Thank you,
Ryan Carley

eugene May 2, 2007 08:49

Have you tried OF1.4 with the
 
Have you tried OF1.4 with the MULES scheme for gamma yet?

You categorically cannot run Gamma with a scheme that is not strictly bounded between 0 and 1, e.g. MULES or gamma01

eugene May 2, 2007 08:59

Belay that, just check the OF1
 
Belay that, just check the OF1.4 tutorials for what schemes to use on gamma.


All times are GMT -4. The time now is 05:42.