[jessica_ict]

Dear all,
I have a problem with deep water simulation.
Wavelength would become larger as wave propagation.
Could someone tell me how to solve the problem?

The following are my file:

waveProperties:

seaLevel	0.00;

// A list of the relaxation zones in the simulation. The parameters are given
// in <name>Coeffs below.
relaxationNames (inlet outlet);

initializationName outlet;

inletCoeffs
{
    // Wave type to be used at boundary "inlet" and in relaxation zone "inlet"
    waveType    stokesSecond;  
    
    // Ramp time of 2 s
    Tsoft       1.2;

    // Water depth at the boundary and in the relaxation zone
    depth       0.900000;

    // Wave period
    period      1.20;

    // Phase shift in the wave
    phi         0.000000;

    // Wave number vector, k. 
    direction  (1.0 0.0 0.0);

    // Wave height
    height      0.06;
    debug       false;
    
    // Specifications on the relaxation zone shape and relaxation scheme
    relaxationZone
    {
        relaxationScheme Spatial;
        relaxationShape  Rectangular;
        beachType        Empty;
    
        relaxType   INLET;
        startX      (0.0  0.0 -0.9);
        endX        (6.0  0.9  0.3);
        orientation      (1.0 0.0 0.0);
    }
};

outletCoeffs
{
    waveType    potentialCurrent;
    U           (0 0 0);
    Tsoft      	1.2;

    relaxationZone
    {
        relaxationScheme Spatial;
        relaxationShape  Rectangular;
        beachType        Empty;    

        relaxType   OUTLET;
        startX      (29.0  0.0 -0.9);
        endX        (35.0  0.9  0.3);
        orientation      (1.0 0.0 0.0);
    }
};

controlDict:

application interFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         60;

deltaT          0.001;

writeControl    adjustableRunTime;

writeInterval   0.1;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  yes;

maxCo           0.25;

maxAlphaCo      0.25;

maxDeltaT       0.001;

fvSolution

solvers
{
    "alpha.water.*"
    {
        nAlphaCorr      1;
        nAlphaSubCycles 1;
        alphaOuterCorrectors yes;
        cAlpha          1;

        MULESCorr       yes;
        nLimiterIter    3;

        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-8;
        relTol          0;
    }

    pcorr GAMG
    {
        tolerance        1e-7;
        relTol           0.0;

        smoother         DIC;//GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        nFinestSweeps    2;

        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator     faceAreaPair;
        mergeLevels      1;
    };

    pcorrFinal GAMG
    {
        tolerance        1e-7;
        relTol           0.0;

        smoother         DIC;//GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        nFinestSweeps    2;

        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator     faceAreaPair;
        mergeLevels      1;
    };

    p_rgh GAMG
    {
        tolerance        1e-7;
        relTol           0.0;

        smoother         DIC;//GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        nFinestSweeps    2;

        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator     faceAreaPair;
        mergeLevels      1;
    };

    p_rghFinal GAMG
    {
        tolerance        1e-8;
        relTol           0.0;

        smoother         DIC;//GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        nFinestSweeps    2;

        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator     faceAreaPair;
        mergeLevels      1;
    };

    U PBiCG
    {
        preconditioner   DILU;
        tolerance        1e-09;
        relTol           0;
    };

    UFinal PBiCG
    {
        preconditioner   DILU;
        tolerance        1e-09;
        relTol           0;
    };

    gamma PBiCG
    {
        preconditioner   DILU;
        tolerance        1e-07;
        relTol           0;
    };
}


PIMPLE 
{ 
    momentumPredictor yes;
    nOuterCorrectors 1; 
    nCorrectors     3;
    nNonOrthogonalCorrectors 1;
}

relaxationFactors
{
    fields
    {
    }
    equations
    {
        ".*" 1;
    }
}

fvScheme

ddtSchemes
{
    default Euler;
}

gradSchemes
{
//    default	cellLimited fourth 1;
    default         Gauss linear;
    grad(U)         Gauss linear;
    grad(alpha1)     Gauss linear;
}

divSchemes
{
//    default	    Gauss linear;
    div(rhoPhi,U)  Gauss limitedLinearV 1;
//    div(phi,gamma)  Gauss vanLeer;
//    div(rho*phi,U)  Gauss MUSCL;
//    div((muEff*dev(T(grad(U))))) Gauss linear;
    div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
    div(phi,alpha)  Gauss MUSCL;
    div(phirb,alpha) Gauss interfaceCompression;
//    div(rhoPhi,U)   Gauss limitedLinearV 1;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p_rgh;
    pcorr;
    alpha.water;
}

domain
x:35m z:1.2m
dx:0.005m dz:0.0025

wave condition
period:1.2 sec
wave height:0.06m
water depth:0.9m
This is deep water condition!
There are 24 cells per wave height and about 439 cells per wavelength.

I tried two versions of OpenFOAM (1712plus and extend 4.0), different types of mesh and different timesteps.

The result of different timesteps, version and mesh type shown below:

[larry k]

Quick answer: You need to check your numerical schemes for example, from my experience, CrankNicolson works best than euler

[ngj]

Also, if you compare the conditions with stream function wave theory, then you will see that stream function wave theory is roughly 1% longer, so after 13 wave lengths it amounts to a noticeable effect.



Kind regards


Niels

[jessica_ict]

@ngj
Dear Niels,
Thanks for your quick reply.
I found that the result is much more approach to Stokes 5th wave, not Stokes 2nd waves.
Would you please tell me why the wave condition is appropriate to choose Stokes 2nd Wave, but the result is more approach to Stokes 5th wave?
Thank you very much!