CFD Online Discussion Forums - Oscillating behaviour when mesh gets too small

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;

}