畢業了——課題代碼開源（三）使用Palabos的自由表面流模型仿複雜多孔介質中的液滴滲透

簡介

對於多相流模擬，Palabos中也是實現了很多，比如shanchen模型做的瑞麗-泰勒不平衡和兩相混合器，還有helee模型做的雙液滴碰撞，怎麼說呢，我都跑過，但是，由於我的體系是氣體和水，密度比極大，爲了能順利畢業，最終我選擇了palabos裏的自由表面流動模型來進行模擬，是通過原始案例中的潰壩，改造而成的，忽略了氣相，只考慮液滴在複雜多孔介質中的滲透時，每一時間步的界面位置。選擇這個模型的主要原因，因爲改起來簡單，模型封裝的很徹底，接觸角不需要我再查文獻設置，很多的邊界條件都被封裝爲一個單一的枚舉值，通過該枚舉值進行調用，很適合堆數據。

代碼

#include "palabos3D.h"
#include "palabos3D.hh"

using namespace plb;

#define DESCRIPTOR descriptors::ForcedD3Q19Descriptor

typedef double T;

// Smagorinsky constant for LES model.
// const T cSmago = 0.14;

T lx;
T ly;
T lz;

const T rhoEmpty = T(1);
const T rho = T(1000);
    
plint writeImagesIter   = 400;
plint getStatisticsIter = 20;

plint maxIter;
plint N;
plint nx, ny, nz;
T delta_t, delta_x;
Array<T,3> externalForce;
T nuPhys, nuLB, tau, omega, surfaceTensionPhys, surfaceTensionLB, contactAngle;

std::string fNameIn,fNameOut;

void readGeometry(std::string fNameIn, std::string fNameOut, MultiScalarField3D<int>& geometry)
{
    const plint nx = geometry.getNx();
    const plint ny = geometry.getNy();
    const plint nz = geometry.getNz();

    Box3D sliceBox(0,0, 0,ny-1, 0,nz-1);
    std::auto_ptr<MultiScalarField3D<int> > slice = generateMultiScalarField<int>(geometry, sliceBox);
    plb_ifstream geometryFile(fNameIn.c_str());
    for (plint iX=0; iX<nx; ++iX) {
        if (!geometryFile.is_open()) {
            pcout << "Error: could not open geometry file " << fNameIn << std::endl;
            exit(EXIT_FAILURE);
        }
        geometryFile >> *slice;
        copy(*slice, slice->getBoundingBox(), geometry, Box3D(iX,iX, 0,ny-1, 0,nz-1));
    }

    /*{
        VtkImageOutput3D<T> vtkOut("porousMediumOrigin", 1.0);
        vtkOut.writeData<float>(*copyConvert<int,T>(geometry, geometry.getBoundingBox()), "tag", 1.0);
    }*/

    /*{
        std::auto_ptr<MultiScalarField3D<T> > floatTags = copyConvert<int,T>(geometry, geometry.getBoundingBox());
        std::vector<T> isoLevels;
        isoLevels.push_back(0.5);
        typedef TriangleSet<T>::Triangle Triangle;
        std::vector<Triangle> triangles;
        Box3D domain = floatTags->getBoundingBox().enlarge(-1);
        domain.x0++;
        domain.x1--;
        isoSurfaceMarchingCube(triangles, *floatTags, isoLevels, domain);
        TriangleSet<T> set(triangles);
        std::string outDir = fNameOut + "/";
        set.writeBinarySTL(outDir + "porousMedium.stl");
    }*/
}

void setupParameters() {
    delta_x = 0.001 / N;
    lx = nx*delta_x;
    ly = ny*delta_x;
    lz = nz*delta_x;

    // Gravity in lattice units.
    T gLB = 9.8 * delta_t * delta_t/delta_x;
    externalForce  = Array<T,3>(0., 0., -gLB);
    tau            = (nuPhys*DESCRIPTOR<T>::invCs2*delta_t)/(delta_x*delta_x) + 0.5;
    omega          = 1./tau;    
    nuLB           = (tau-0.5)*DESCRIPTOR<T>::cs2; // Viscosity in lattice units.
    
    surfaceTensionLB = (rhoEmpty / rho) * (delta_t*delta_t) / (delta_x*delta_x*delta_x) * surfaceTensionPhys;
}

bool insideFluid(T x, T y, T z)
{
    Array<T,3> pos(x, y, z);
    Array<T,3> center(nx/2.0, ny/2.0, 0);
    T r = norm(pos-center);
    if (r <= nz/25) {
        return true;
    }
    return false;
}

int initialFluidFlags(plint iX, plint iY, plint iZ) {
    if (insideFluid(iX, iY, iZ)) {
        return freeSurfaceFlag::fluid;
    }
    else {
        return freeSurfaceFlag::empty;
    }
}

void porousMediaSetup(FreeSurfaceFields3D<T,DESCRIPTOR>& fields,
        MultiScalarField3D<int>& geometry)
{
    //integrateProcessingFunctional(new ShortenBounceBack3D<T,DESCRIPTOR>, fields.lattice.getBoundingBox(), fields.freeSurfaceArgs, 0);
    // Set all outer-wall cells to "wall" (here, bulk-cells are also set to "wall", but it
    // doesn't matter, because they are overwritten on the next line).
    setToConstant(fields.flag, fields.flag.getBoundingBox(), (int)freeSurfaceFlag::wall);
    setToFunction(fields.flag, fields.flag.getBoundingBox().enlarge(-1), initialFluidFlags);

    setToConstant(fields.flag, geometry, 1,
                   fields.flag.getBoundingBox().enlarge(-1), (int)freeSurfaceFlag::wall);

    /*setToConstant(fields.flag, Box3D(6*nx/13, 7*nx/13, 6*ny/13, 7*ny/13, 0, 0), (int)freeSurfaceFlag::fluid);
    setToConstant(fields.flag, Box3D(5*nx/11, 6*nx/11, 5*ny/11, 6*ny/11, 1, nx/11), (int)freeSurfaceFlag::fluid);*/

    setToConstant(fields.flag, Box3D(9*nx/19, 10*nx/19, 9*ny/19, 10*ny/19, 0, nz/38), (int)freeSurfaceFlag::fluid);

    //pcout << "5" << std::endl;
    fields.periodicityToggle(2,false);
    fields.periodicityToggle(1,false);
    fields.periodicityToggle(0,false);

    fields.defaultInitialize();

    /*VtkImageOutput3D<T> vtkOut("porousMedium", 1.0);
        vtkOut.writeData<float>(*copyConvert<int,T>(fields.flag, fields.flag.getBoundingBox()), "tag", 1.0);*/
}

void writeResults(MultiBlockLattice3D<T,DESCRIPTOR>& lattice, MultiScalarField3D<T>& volumeFraction, plint iT)
{
    static const plint nx = lattice.getNx();
    static const plint ny = lattice.getNy();
    static const plint nz = lattice.getNz();

    const plint imSize = 600;
    Box3D slice(0, nx-1, ny/2, ny/2, 0, nz-1);
    ImageWriter<T> imageWriter("leeloo");
    imageWriter.writeScaledGif(createFileName("u", iT, 6),
                               *computeVelocityNorm(lattice, slice),
                               imSize, imSize); 

    imageWriter.writeScaledGif(createFileName("rho", iT, 6),
                               *computeDensity(lattice, slice),
                               imSize, imSize);
                   
    imageWriter.writeScaledGif(createFileName("volumeFraction", iT, 6), *extractSubDomain(volumeFraction, slice),
                               imSize, imSize);

    // Use a marching-cube algorithm to reconstruct the free surface and write an STL file.
    /*std::vector<T> isoLevels;
    isoLevels.push_back((T) 0.5);
    typedef TriangleSet<T>::Triangle Triangle;
    std::vector<Triangle> triangles;
    isoSurfaceMarchingCube(triangles, volumeFraction, isoLevels, volumeFraction.getBoundingBox());
    TriangleSet<T>(triangles).writeBinarySTL(createFileName(fNameOut+"/interface", iT, 6)+".stl");*/

    VtkImageOutput3D<T> vtkOut(createFileName("volumeFraction", iT, 6), 1.);
    vtkOut.writeData<float>(volumeFraction, "vf", 1.);
}

void writeStatistics(FreeSurfaceFields3D<T,DESCRIPTOR>& fields) {
    pcout << " -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- " << std::endl;
    T averageMass = freeSurfaceAverageMass<T,DESCRIPTOR>(fields.freeSurfaceArgs, fields.lattice.getBoundingBox());
    pcout << "Average Mass: " << averageMass  << std::endl;
    T averageDensity = freeSurfaceAverageDensity<T,DESCRIPTOR>(fields.freeSurfaceArgs, fields.lattice.getBoundingBox());
    pcout << "Average Density: " << std::setprecision(12) << averageDensity  << std::endl;

    T averageVolumeFraction = freeSurfaceAverageVolumeFraction<T,DESCRIPTOR>(fields.freeSurfaceArgs, fields.lattice.getBoundingBox());
    pcout << "Average Volume-Fraction: " << std::setprecision(12) << averageVolumeFraction  << std::endl;

    pcout << " -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- " << std::endl;
}

int main(int argc, char **argv)
{
    plbInit(&argc, &argv);
        
    if (global::argc() != 12) {
        pcout << "Error missing some input parameter\n";
    }

    try {
        global::argv(1).read(fNameOut);
        global::directories().setOutputDir(fNameOut+"/");

        global::argv(2).read(nuPhys);
        global::argv(3).read(surfaceTensionPhys);
        global::argv(4).read(contactAngle);
        global::argv(5).read(N);
        global::argv(6).read(delta_t);
        global::argv(7).read(maxIter);
        global::argv(8).read(nx);
        global::argv(9).read(ny);
        global::argv(10).read(nz);
        global::argv(11).read(fNameIn);
    }
    catch(PlbIOException& except) {
        pcout << except.what() << std::endl;
        pcout << "The parameters for this program are :\n";
        pcout << "1. Output directory name.\n";
        pcout << "2. kinematic viscosity in physical Units (m^2/s) .\n";
        pcout << "3. Surface tension in physical units (N/m).\n";
        pcout << "4. Contact angle (in degrees).\n";
        pcout << "5. number of lattice nodes for lz .\n";
        pcout << "6. delta_t .\n"; 
        pcout << "7. maxIter .\n";
        pcout << "Reasonable parameters on a parallel machine are: " << (std::string)global::argv(0) << "tmp 1.01e-6 0.0728 150.0 1000 1.e-8 80000 501 501 501 RawData.dat\n";
        exit (EXIT_FAILURE);
    }
    
    setupParameters();

    pcout << "Reading the geometry file." << std::endl;
    MultiScalarField3D<int> geometry(nx,ny,nz);
    readGeometry(fNameIn, fNameOut, geometry);
    MultiScalarField3D<int> inputgeometry(nx,ny,nz/2+1);
    copy(geometry, Box3D(0,nx-1,0,ny-1,0,nz/2), inputgeometry, inputgeometry.getBoundingBox());
    
    pcout << "delta_t= " << delta_t << std::endl;
    pcout << "delta_x= " << delta_x << std::endl;
    pcout << "delta_t*delta_t/delta_x= " << delta_t*delta_t/delta_x << std::endl;
    pcout << "externalForce= " << externalForce[2] << std::endl;
    pcout << "surfaceTensionLB= " << surfaceTensionLB << std::endl;
    pcout << "relaxation time= " << tau << std::endl;
    pcout << "omega= " << omega << std::endl;
    pcout << "kinematic viscosity physical units = " << nuPhys << std::endl;
    pcout << "kinematic viscosity lattice units= " << nuLB << std::endl;

    global::timer("initialization").start();

    //pcout << "1" << std::endl;

    SparseBlockStructure3D blockStructure(createRegularDistribution3D(nx, ny, nz/2+1));

    //pcout << "2" << std::endl;

    /*Dynamics<T,DESCRIPTOR>* dynamics
        = new SmagorinskyBGKdynamics<T,DESCRIPTOR>(omega, cSmago);*/
    Dynamics<T,DESCRIPTOR>* dynamics = new IncBGKdynamics<T,DESCRIPTOR>(omega);

    FreeSurfaceFields3D<T,DESCRIPTOR> fields( blockStructure, dynamics->clone(), rhoEmpty,
                                              surfaceTensionLB, contactAngle, externalForce );
    porousMediaSetup(fields, inputgeometry);

    std::vector<MultiBlock3D*> freeSurfaceArgs = aggregateFreeSurfaceParams(fields.lattice, fields.rhoBar, fields.j, fields.mass, fields.volumeFraction,
                    fields.flag, fields.normal, fields.helperLists, fields.curvature, fields.outsideDensity);
    
    Array<T,3> injectionVelocity((T)0.,(T)0.,(T)0.1);

    pcout << "Time spent for setting up lattices: "
          << global::timer("initialization").stop() << std::endl;
    T lastIterationTime = T();

    //pcout << "6" << std::endl;

    for (plint iT = 0; iT <= maxIter; ++iT) {
        global::timer("iteration").restart();
        
        T sum_of_mass_matrix = T();
        T lost_mass = T();
        if (iT % getStatisticsIter==0) {
            pcout << std::endl;
            pcout << "ITERATION = " << iT << std::endl;
            pcout << "Time of last iteration is " << lastIterationTime << " seconds" << std::endl;
            writeStatistics(fields);
            sum_of_mass_matrix = fields.lattice.getInternalStatistics().getSum(0);
            pcout << "Sum of mass matrix: " << sum_of_mass_matrix << std::endl;
            lost_mass = fields.lattice.getInternalStatistics().getSum(1);
            pcout << "Lost mass: " << lost_mass << std::endl;
            pcout << "Total mass: " << sum_of_mass_matrix + lost_mass << std::endl;
            pcout << "Interface cells: " << fields.lattice.getInternalStatistics().getIntSum(0) << std::endl;
        }

        if (iT % writeImagesIter == 0) {
            global::timer("images").start();
            writeResults(fields.lattice, fields.volumeFraction, iT);
            pcout << "Total time spent for writing images: "
                << global::timer("images").stop() << std::endl;
        }                           

        // This includes the collision-streaming cycle, plus all free-surface operations.
        fields.lattice.executeInternalProcessors();
        /*applyProcessingFunctional (
            new PouringLiquid3D<T,DESCRIPTOR>(dynamics->clone(), injectionVelocity), 
                                   Box3D(4*nx/9, 5*nx/9, 4*ny/9, 5*ny/9, 0, 0), freeSurfaceArgs );*/
        applyProcessingFunctional ( 
            new PouringLiquid3D<T,DESCRIPTOR>(dynamics->clone(), injectionVelocity), 
                                   Box3D(9*nx/19, 10*nx/19, 9*ny/19, 10*ny/19, 0, 0), freeSurfaceArgs );
        fields.lattice.evaluateStatistics();
        fields.lattice.incrementTime();

        lastIterationTime = global::timer("iteration").stop();
    }
}

說明

怎麼說呢，這應該算是一隻超級縫合怪，滲透案例的複雜結構讀入，對格子描述符的嘗試，與潰壩同案例文件夾下的vof兩相流模型中的部分設置，看模型源代碼找到的模型已封裝好的速度邊界條件的接口，嗯，這應該是我palabos中最費心的一個代碼了。當然了，雖然我拿着個畢業，但實際上我能寫的東西已經遠遠超過了當初寫這個代碼時的水平，分享了其實也不心疼。給小朋友們留一個可以參考的對象其實蠻好的，哈哈哈！
如果看不懂不要緊，以後我也會逐個解析案例。
無圖無真相

完