CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Oscillating behaviour when mesh gets too small

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   January 9, 2014, 06:04
Default Oscillating behaviour when mesh gets too small
  #1
New Member
 
James B
Join Date: Oct 2013
Posts: 4
Rep Power: 3
james91 is on a distinguished road
Dear Foamers


I am simulating detonations with a 2nd order approximate Riemann Solver. The results are smooth when I have a relative coarse mesh size of 1 mm but when I refine my mesh the solver starts to oscillate in every variable (see figure), would you have any idea on how to solve this problem or where it comes from ? (Maybe adapting the FVScheme and add more dissipation)?
The mesh is a 1D shocktube (1 cell with upper and lower BC symmetry conditions imposed)

Thank you very much!!

Here is the FvScheme from DDTFoam

Code:
ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
    grad(scalarSlope)    cellMDLimited Gauss linear 1;
    grad(USlope)    cellMDLimited Gauss linear 1;
}

divSchemes
{
    default         none;

    div(tauShear)            Gauss linear;
    div(tauMC)                Gauss linear;
    div((tauShear&U))        Gauss linear;
    div((p*U))            Gauss linear;

    div((U+((sL*Xi)*-grad(c)))) Gauss linear;
    div((sL*grad(b)))         Gauss linear;
    div(U)                 Gauss linear;
    div((sL*-grad(c)))         Gauss linear;
    
    div(phiSt,c)        Gauss vanLeer01;    
    div(phiXi,Xi)    Gauss vanLeer;
    
    div(phi,k)              Gauss upwind;
    div(phi,epsilon)     Gauss upwind; 
    div(phi,omega)     Gauss upwind; 
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{

    default none;
    
    interpolate(tauMC) Gamma phi 1.0;
    interpolate(mu) Gamma phi 1.0;
    interpolate(muEff) Gamma phi 1.0;
    
    reconstruct(rho) limitedLinear 1.0;
    reconstruct(U)   limitedLinearV 1.0;
    reconstruct(T)   limitedLinear 1.0;

    interpolate(rho) linear;         // for CFL
    reconstruct(cSound) linear;     // for CFL
    
    interpolate(p) linear;           // for MinMax scheme    
    interpolate(Teff) linear;         // for MinMax scheme
    interpolate(tau) linear;          // for MinMax scheme

    interpolate(-grad(c)) linear;
    interpolate(grad((1-c))) linear;
    interpolate((((p*psiu)*sL)*Xi)) linear;
    interpolate((sL*((1|Xi)-Xi))) linear;
    interpolate(((rhoUnburned*sL)*Xi)) linear;
    interpolate((laplacian(interpolate(alphaEff),c)|mag(-grad(c)))) linear;
}

snGradSchemes
{
    default         corrected;
}
Attached Images
File Type: png oscillations.png (83.8 KB, 21 views)
james91 is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
SnappyHexMesh for internal Flow vishwa OpenFOAM Native Meshers: snappyHexMesh and Others 23 August 6, 2014 03:50
[ICEM] Unstructure Meshing Around Imported Plot3D Structured Mesh ICEM kawamatt2 ANSYS Meshing & Geometry 17 December 20, 2011 12:45
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55
Gambit: mesh size to small??? Ralf Schmidt FLUENT 1 January 28, 2006 02:26
unstructured vs. structured grids Frank Muldoon Main CFD Forum 1 January 5, 1999 11:09


All times are GMT -4. The time now is 22:04.