[a.aralnu]

I'm trying to do a steady state simulation of the flow over a 3D NACA2412 airfoil at Re = 400, 000. I'm using a structured D grid mesh around the airfoil which I made in ICEM CFD. I plan on using the solution to initialize an URANS simulation and then use this other solution to initialize an hybrid URANS-LES simulation (this is the reason why I'm using a 3D domain instead of 2D, to be able to capture the 3D characteristics of turbulence). I'm using Menter's k-w SST model to account for turbulence.

The problem I'm facing is I have divergence in continuity residuals whenever I use 2nd order schemes for U, k, w and Nu. Everything blows up at around 30-100 iterations. If I use 1st order schemes it converges up to a certain point, however when I check the solution the velocity and pressure fields look VERY bad and completly non-physical. I attached a picture of the velocity field both in zoom out and around the airfoil.

I've tinkered with different solvers and it doesn't seem to help. I've also tried different boundary conditions and the problem persists.

I've also tried different configurations of the mesh. All my meshes pass all the checks in checkMesh command (first attempts had cells with very high Aspect Ratio due to a very small first layer around airfoil but I fixed it). I believe my mesh is very good but I still can't get a good solution. I attached a picture of the overall mesh and the boundary layer inflation (looking for y+ = 2.5, 1st layer height = 5.3 x10 ^-5).

The checkMesh output is this:

Mesh stats
    points:           6177168
    faces:            18194892
    internal faces:   17860782
    cells:            6009279
    faces per cell:   6
    boundary patches: 6
    point zones:      0
    face zones:       1
    cell zones:       1

Overall number of cells of each type:
    hexahedra:     6009279
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    outlet              10246    10512    ok (non-closed singly connected)  
    inlet               13019    13344    ok (non-closed singly connected)  
    airfoil             13019    13296    ok (non-closed singly connected)  
    farfield            42112    43104    ok (non-closed singly connected)  
    periodic_1          127857   128691   ok (non-closed singly connected)  
    periodic_2          127857   128691   ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-7.84575217306 -8.00000004259 -2.975397706e-14) (32.1500015259 8.00000004482 3)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-1.28045831943e-17 -6.02975755126e-16 1.48804105861e-16) OK.
    Max cell openness = 1.38576603359e-15 OK.
    Max aspect ratio = 604.605564814 OK.
    Minimum face area = 1.91070015499e-07. Maximum face area = 0.100408280885.  Face area magnitudes OK.
    Min volume = 1.21959584361e-08. Max volume = 0.00640903919807.  Total volume = 1837.26653156.  Cell volumes OK.
    Mesh non-orthogonality Max: 34.1024120585 average: 5.48223143195
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.275168817637 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

The domain has the following dimensions:

Upstream radius = 8m
Downstream length = 32m
z direction span = 3m
airfoil chord = 1m

Initial conditions are:
k:

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0.0006;

boundaryField
{
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 0.0006;
        value           uniform 0.0006;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 0.0006;
    }
    airfoil
    {
        type            fixedValue;
        value           uniform 1e-20;
    }
    periodic_1
    {
        type            cyclic;
    }
    periodic_2
    {
        type            cyclic;
    }
    farfield
    {
        type            freestream;
        freestreamValue $internalField;
    }
}

w:

dimensions      [0 0 -1 0 0 0 0];

internalField   uniform 0.024495;

boundaryField
{
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 0.024495;
        value           uniform 0.024495;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 0.024495;
    }
    airfoil
    {
        type            omegaWallFunction;
        value           uniform 0.024495;
    }
    periodic_1
    {
        type            cyclic;
    }
    periodic_2
    {
        type            cyclic;
    }
    farfield
    {
        type            freestream;
        freestreamValue $internalField;
    }
}

U

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (4 0 0);

boundaryField
{
    outlet
    {
        type            inletOutlet;
        inletValue      uniform (4 0 0);
        value           uniform (4 0 0);
    }
    inlet
    {
        type            fixedValue;
        value           uniform (4 0 0);
    }
    airfoil
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    periodic_1
    {
        type            cyclic;
    }
    periodic_2
    {
        type            cyclic;
    }
    farfield
    {
        type            freestreamVelocity;
        freestreamValue $internalField;
    }
}

p:

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }
    inlet
    {
        type            zeroGradient;
    }
    airfoil
    {
        type            zeroGradient;
    }
    periodic_1
    {
        type            cyclic;
    }
    periodic_2
    {
        type            cyclic;
    }
    farfield
    {
        type            freestreamPressure;
        freestreamValue $internalField;
    }
}

Sorry for the long post but I'm becoming desperate, I've been trying to run this for a long time now.

If anyone is able to help or give me any ideas on what I can do to fix my problem I'll be eternally grateful!! Thank you in advance.

[ErenC]

Your max aspect ratio is 600, that's "pretty" high.