[steddy]

I'm trying to simulate an Ahmed body.
Overall, the simulation setup is identical to the of the Motorbike tutorial (k-w SST).

I only changed the following stuff:

- Turbulence variables (taken from this Simscale validation project):
flowVelocity: 63.7 m/s
k: 21.9
w: 29215

- I enlarged the wind tunnel

- I changed the ollowing conditions:

fvSchemes:

ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default         Gauss linear;
    grad(U)         cellLimited Gauss linear 1;
}

divSchemes
{
    default         none;
    div(phi,U)      Gauss linearUpwindV Gauss linear;
    div(phi,k)      Gauss linear;
    div(phi,omega)  Gauss linear;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}

fvSolution:

solvers
{
    p
    {
        solver          GAMG;
        smoother        GaussSeidel;
        tolerance       1e-7;
        relTol          0.001;
    }

    Phi
    {
        $p;
    }

    U
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-8;
        relTol          0.01;
        nSweeps         1;
    }

    k
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-8;
        relTol          0.01;
        nSweeps         1;
    }

    omega
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-8;
        relTol          0.01;
        nSweeps         1;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 0;
}

potentialFlow
{
    nNonOrthogonalCorrectors 10;
}

relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        U               0.7;
        k               0.7;
        omega           0.7;
    }
}

cache
{
    grad(U);
}

Take a look at the residuals graph. At ~1800 time steps, the simulation seems to have converged; however, the residuals suddenly go crazy.

These are the cutting planes for the Pressure and Velocity taken at about 2000 time steps (spoiler: nothing good. A few iterations later the simulation crashed).

Here there are the log.simpleFoam, log.snappyHexMesh files.
Mesh seems to be fine:

Overall number of cells of each type:
    hexahedra:     1756966
    prisms:        3473
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     30027
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            4   20
            5   83
            6   2629
            7   1044
            8   206
            9   24319
           10   20
           12   1570
           15   116
           18   20

[...]
Checking geometry...
    Overall domain bounding box (-2 0 -4.33681e-19) (9 3 5)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (1.62399e-15 -3.55151e-15 -2.00762e-17) OK.
    Max cell openness = 3.71841e-16 OK.
    Max aspect ratio = 18.9396 OK.
    Minimum face area = 9.28447e-07. Maximum face area = 0.00396961.  Face area magnitudes OK.
    Min volume = 1.68502e-09. Max volume = 0.000248606.  Total volume = 164.945.  Cell volumes OK.
    Mesh non-orthogonality Max: 64.0492 average: 4.45301
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 3.38809 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

Do you have any idea what is going on?