Merge branch 'porous-media-showcase' into 'master'

Add showcase for simulation of flow through porous media

See merge request walberla/walberla!441

apps/showcases/CMakeLists.txt

@@ -6,3 +6,6 @@ add_subdirectory( PegIntoSphereBed )
 if ( WALBERLA_BUILD_WITH_CODEGEN AND WALBERLA_BUILD_WITH_PYTHON )
 add_subdirectory( PhaseFieldAllenCahn )
 endif()
+if ( WALBERLA_BUILD_WITH_CODEGEN AND NOT WALBERLA_BUILD_WITH_OPENMP)
+   add_subdirectory( PorousMedia )
+endif()

apps/showcases/PorousMedia/CMakeLists.txt

+waLBerla_link_files_to_builddir( *.prm )
+waLBerla_link_files_to_builddir( *.txt )
+
+waLBerla_add_executable (
+        NAME PackedBedCreation
+        FILES PackedBedCreation.cpp
+        DEPENDS blockforest core field geometry timeloop pe pe_coupling vtk)
+
+waLBerla_generate_target_from_python(
+        NAME GeneratedLatticeModel
+        FILE PorousMediaCumulantLBMKernel.py
+        OUT_FILES LbCodeGen_LatticeModel.cpp LbCodeGen_LatticeModel.h)
+
+waLBerla_add_executable (
+        NAME PorousMedia
+        FILES PorousMediaCumulantLBMKernel.py PorousMedia.cpp
+        DEPENDS blockforest core field lbm geometry timeloop pe pe_coupling GeneratedLatticeModel )
+

apps/showcases/PorousMedia/PackedBedCreation.cpp

+//======================================================================================================================
+//
+//  This file is part of waLBerla. waLBerla is free software: you can
+//  redistribute it and/or modify it under the terms of the GNU General Public
+//  License as published by the Free Software Foundation, either version 3 of
+//  the License, or (at your option) any later version.
+//
+//  waLBerla is distributed in the hope that it will be useful, but WITHOUT
+//  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+//  for more details.
+//
+//  You should have received a copy of the GNU General Public License along
+//  with waLBerla (see COPYING.txt). If not, see <http://www.gnu.org/licenses/>.
+//
+//! \file PackedBedCreation.cpp
+//! \author Christoph Schwarzmeier <christoph.schwarzmeier@fau.de>
+//
+//======================================================================================================================
+
+//======================================================================================================================
+// This showcase creates a packed bed consisting of spherical particles by simulating a sedimentation process using
+// rigid body dynamics. It must be given a parameter file as command-line argument, such as "PackedBedCreation.prm". The
+// resulting porous medium is periodic in two directions and the location of the spherical particles are written to a
+// file in which the particle positions are denoted relative to the particles' diameter.
+// In the simulation, the spherical particles fall into a "box" due to a gravitational acceleration. The box is periodic
+// in the side-directions (x- and y-directions) but bound by a solid plane at the bottom (in z-direction). The spheres
+// are initially generated on top of the domain in a structured order with slight random disturbances. Once the
+// particles have settled (according to their velocity), all particles with center point closer than three particle
+// diameters to the bottom plane are removed. This is intended to reduce the influence of the bottom plane on the
+// geometry creation of the packed bed. Finally, the packed bed is shifted upwards such that it is placed in the center
+// of the domain.
+//======================================================================================================================
+
+
+#include "blockforest/all.h"
+
+#include "core/Environment.h"
+#include "core/grid_generator/all.h"
+#include "core/mpi/MPITextFile.h"
+#include "core/timing/RemainingTimeLogger.h"
+
+#include "pe/basic.h"
+#include "pe/synchronization/SyncShadowOwners.h"
+#include "pe/utility/DestroyBody.h"
+#include "pe/vtk/SphereVtkOutput.h"
+
+#include "vtk/VTKOutput.h"
+
+#include <string>
+#include <tuple>
+
+namespace walberla
+{
+///////////
+// USING //
+///////////
+
+using BodyTypeTuple = std::tuple< pe::Plane, pe::Sphere >; // must contain all body types used in this simulation
+
+///////////////
+// UTILITIES //
+///////////////
+
+// write the particles' locations (non-dimensionalized with particle diameter) to file
+void writePorousGeometry(BlockForest& blockForest, BlockDataID bodyStorageID, uint_t particleDiameter,
+                         const std::string& filename);
+
+// get the absolute maximum velocity of all particles
+real_t getParticleMaxVel(BlockForest& blockForest, const BlockDataID& bodyStorageID);
+
+////////////////
+// PARAMETERS //
+////////////////
+
+// data structure class for storing basic parameters
+struct Setup
+{
+   Vector3< uint_t > numBlocks;  // number of blocks (= processes) in x,y,z, direction
+   Vector3< uint_t > domainSize; // domain size in x,y,z direction
+
+   uint_t particleDiameter; // cells per diameter of the particles
+
+   uint_t numInitialParticles; // number of initially created particles (some spheres at the bottom will be removed)
+   uint_t maxTimesteps;        // maximum number of PE timesteps (if convergence criterion is not fulfilled)
+   real_t convVelocity; // velocity at which the particles are considered stationary and the simulation is converged
+
+   uint_t maxIterations;                       // number of maximum iterations of the physics engine (PE) contact solver
+   real_t relaxationParameter;                 // relaxation parameter of the PE contact solver
+   Vector3< real_t > globalLinearAcceleration; // global linear acceleration (= force) of the PE contact solver
+   real_t dt;                                  // temporal resolution of the PE contact solver
+
+   std::string porousGeometryFile; // filename of the output file that defines the packed bed
+   uint_t vtkInterval;             // frequency at which vtk output is written
+
+   void printSetup()
+   {
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(numBlocks);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(particleDiameter);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(domainSize);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(numInitialParticles);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(maxTimesteps);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(convVelocity);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(maxIterations);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(relaxationParameter);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(globalLinearAcceleration);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(dt);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(porousGeometryFile);
+      WALBERLA_LOG_DEVEL_VAR_ON_ROOT(vtkInterval);
+   }
+}; // struct Setup
+
+//////////
+// MAIN //
+//////////
+
+int main(int argc, char** argv)
+{
+   Environment walberlaEnv(argc, argv);
+
+   if (argc < 2) { WALBERLA_ABORT("Please specify a parameter file as input argument."); }
+
+   Setup setup;
+
+   ///////////////////////////
+   // SIMULATION PROPERTIES //
+   ///////////////////////////
+
+   // get parameters from config file
+   auto domainParameters  = walberlaEnv.config()->getOneBlock("DomainParameters");
+   setup.numBlocks        = domainParameters.getParameter< Vector3< uint_t > >("numBlocks");
+   setup.particleDiameter = domainParameters.getParameter< uint_t >("particleDiameter");
+   setup.domainSize       = domainParameters.getParameter< Vector3< uint_t > >("relDomainSize");
+   setup.domainSize *= setup.particleDiameter;
+
+   auto simulationParameters = walberlaEnv.config()->getOneBlock("SimulationParameters");
+   setup.numInitialParticles = simulationParameters.getParameter< uint_t >("numInitialParticles");
+   setup.maxTimesteps        = simulationParameters.getParameter< uint_t >("maxTimesteps");
+   setup.convVelocity        = simulationParameters.getParameter< real_t >("convVelocity");
+
+   auto contactSolverParameters = walberlaEnv.config()->getOneBlock("ContactSolverParameters");
+   setup.maxIterations          = contactSolverParameters.getParameter< uint_t >("maxIterations");
+   setup.relaxationParameter    = contactSolverParameters.getParameter< real_t >("relaxationParameter");
+   setup.globalLinearAcceleration =
+      contactSolverParameters.getParameter< Vector3< real_t > >("globalLinearAcceleration");
+   setup.dt = contactSolverParameters.getParameter< real_t >("dt");
+
+   auto outputParameters    = walberlaEnv.config()->getOneBlock("OutputParameters");
+   setup.porousGeometryFile = outputParameters.getParameter< std::string >("porousGeometryFile");
+   setup.vtkInterval        = outputParameters.getParameter< uint_t >("vtkInterval");
+
+   if (setup.numBlocks[0] < uint_c(3) || setup.numBlocks[1] < uint_c(3))
+   {
+      WALBERLA_ABORT("The number of blocks in x- and y-direction must not be smaller than 3. This is a strict "
+                     "requirement of the PE when using periodic boundaries in these directions.");
+   }
+
+   setup.printSetup();
+
+   //////////////////////
+   // SIMULATION SETUP //
+   //////////////////////
+
+   // axis-aligned bounding box (AABB) that represents the final domain
+   const auto domainAABB = AABB(real_c(0), real_c(0), real_c(0), real_c(setup.domainSize[0]),
+                                real_c(setup.domainSize[1]), real_c(2) * real_c(setup.domainSize[2]));
+
+   // AABB in which the particles are initially positioned before falling down (above domainAABB)
+   const auto genAABB =
+      AABB(real_c(setup.domainSize[0]), real_c(setup.domainSize[1]), real_c(2) * real_c(setup.domainSize[2]), real_c(0),
+           real_c(0), real_c(0.5) * real_c(setup.domainSize[2]));
+
+   // create blockforest with periodicity in side-directions
+   auto forest = blockforest::createBlockForest(domainAABB, setup.numBlocks, Vector3< bool >(true, true, false));
+
+   // generate IDs of specified PE body types
+   pe::SetBodyTypeIDs< BodyTypeTuple >::execute();
+
+   // add global body storage for PE bodies
+   shared_ptr< pe::BodyStorage > globalBodyStorage = make_shared< pe::BodyStorage >();
+
+   // add block-local body storage
+   const auto bodyStorageID = forest->addBlockData(pe::createStorageDataHandling< BodyTypeTuple >(), "bodyStorage");
+
+   // add data-handling for coarse collision detection
+   const auto ccdID =
+      forest->addBlockData(pe::ccd::createHashGridsDataHandling(globalBodyStorage, bodyStorageID), "ccd");
+
+   // add data handling for fine collision detection
+   const auto fcdID = forest->addBlockData(
+      pe::fcd::createGenericFCDDataHandling< BodyTypeTuple, pe::fcd::AnalyticCollideFunctor >(), "fcd");
+
+   // add PE contact solver and set its parameters
+   const auto cr = make_shared< pe::cr::HCSITS >(globalBodyStorage, forest, bodyStorageID, ccdID, fcdID, nullptr);
+   cr->setMaxIterations(setup.maxIterations);
+   cr->setRelaxationModel(
+      pe::cr::HardContactSemiImplicitTimesteppingSolvers::ApproximateInelasticCoulombContactByDecoupling);
+   cr->setRelaxationParameter(setup.relaxationParameter);
+   cr->setGlobalLinearAcceleration(setup.globalLinearAcceleration);
+
+   // create a structure of regularly aligned spherical particles with slight random offsets using a loop; the loop
+   // starts from a certain position and iterates over a pre-defined spacing
+
+   // point at which particle generation starts
+   const Vector3< real_t > genPoint(real_c(0.55) * real_c(setup.particleDiameter),
+                                    real_c(0.55) * real_c(setup.particleDiameter),
+                                    real_c(setup.domainSize[2]) - real_c(0.55) * real_c(setup.particleDiameter));
+
+   uint_t numParticles = uint_t(0);                                     // number of created particles
+   const real_t spacing(real_c(1.25) * real_c(setup.particleDiameter)); // spacing between the particles
+
+   for (auto it = grid_generator::SCIterator(genAABB, genPoint, spacing); it != grid_generator::SCIterator(); ++it)
+   {
+      // create slight random disturbances in the positions of the created particles
+      Vector3< real_t > rndPosDist(real_c(0.1) * math::realRandom< real_t >(-spacing, spacing),
+                                   real_c(0.1) * math::realRandom< real_t >(-spacing, spacing),
+                                   real_c(0.1) * math::realRandom< real_t >(-spacing, spacing));
+
+      // create a sphere particle with default material (iron, cf. src/pe/Materials.h)
+      pe::createSphere(*globalBodyStorage, *forest, bodyStorageID, 0, *it + rndPosDist,
+                       real_c(setup.particleDiameter) * real_c(0.5));
+      ++numParticles;
+      if (numParticles >= setup.numInitialParticles) { break; }
+   }
+
+   // create the bottom plane
+   pe::createPlane(*globalBodyStorage, 1, Vector3< real_t >(0, 0, 1), domainAABB.minCorner());
+
+   // communicate the created particles between processes
+   pe::syncShadowOwners< BodyTypeTuple >(*forest, bodyStorageID);
+
+   // add vtk output for the particles
+   const auto vtkOutput = make_shared< pe::SphereVtkOutput >(bodyStorageID, *forest);
+   const auto vtkWriter = vtk::createVTKOutput_PointData(vtkOutput, "spheres");
+
+   // add vtk output for the domain decomposition
+   vtk::writeDomainDecomposition(forest);
+
+   ///////////////
+   // TIME LOOP //
+   ///////////////
+
+   for (uint_t timestep = uint_c(0); timestep < setup.maxTimesteps; ++timestep)
+   {
+      // check for convergence every 500 time steps
+      if (timestep % uint_c(500) == uint_c(0) && timestep > uint_c(0))
+      {
+         // get the absolute maximum velocity of all particles
+         const auto particleMaxVel = getParticleMaxVel(*forest, bodyStorageID);
+         WALBERLA_LOG_INFO_ON_ROOT("Time step: " << timestep
+                                                 << "\t\tMaximum velocity of all particles: " << particleMaxVel);
+
+         if (particleMaxVel < setup.convVelocity)
+         {
+            WALBERLA_LOG_INFO_ON_ROOT("Converged after " << timestep << " timesteps.")
+            break;
+         }
+      }
+      // perform a PE timestep
+      cr->timestep(setup.dt);
+
+      pe::syncShadowOwners< BodyTypeTuple >(*forest, bodyStorageID); // communicate
+
+      if (timestep % setup.vtkInterval == uint_c(0)) { vtkWriter->write(); }
+   }
+
+   pe::syncShadowOwners< BodyTypeTuple >(*forest, bodyStorageID); // communicate
+
+   ////////////////////
+   // POSTPROCESSING //
+   ////////////////////
+
+   // write settled packed bed to vtk output
+   vtkWriter->write();
+
+   // delete particles the center point of which is below 3 * particleDiameter
+   for (auto blockIt = forest->begin(); blockIt != forest->end(); ++blockIt)
+   {
+      for (auto bodyIt = pe::LocalBodyIterator::begin(*blockIt, bodyStorageID); bodyIt != pe::LocalBodyIterator::end();
+           ++bodyIt)
+      {
+         if (bodyIt->getPosition()[2] < real_c(setup.particleDiameter) * real_c(3)) { bodyIt->markForDeletion(); }
+      }
+   }
+
+   pe::syncShadowOwners< BodyTypeTuple >(*forest, bodyStorageID); // communicate
+
+   // write packed bed after removal of bottom particles to vtk output
+   vtkWriter->write();
+
+   // find position of the lowest and highest particle (closest to bottom and top, respectively) to get the center of
+   // the packed bed
+   real_t lowestPosition  = real_c(domainAABB.maxCorner()[2]); // initialize with the opposite maximum value
+   real_t highestPosition = real_c(domainAABB.minCorner()[2]);
+   for (auto blockIt = forest->begin(); blockIt != forest->end(); ++blockIt)
+   {
+      for (auto bodyIt = pe::LocalBodyIterator::begin(*blockIt, bodyStorageID); bodyIt != pe::LocalBodyIterator::end();
+           ++bodyIt)
+      {
+         real_t zPos = bodyIt->getPosition()[2];
+         if (zPos < lowestPosition) { lowestPosition = zPos; }
+         if (zPos > highestPosition) { highestPosition = zPos; }
+      }
+   }
+
+   // communicate lowest and highest particle positions to all participating processes
+   mpi::allReduceInplace< real_t >(lowestPosition, mpi::MIN);
+   mpi::allReduceInplace< real_t >(highestPosition, mpi::MAX);
+
+   // shift packed bed such that the packed bed's center in z-direction lays in the domain's center in z-direction
+   for (auto blockIt = forest->begin(); blockIt != forest->end(); ++blockIt)
+   {
+      for (auto bodyIt = pe::LocalBodyIterator::begin(*blockIt, bodyStorageID); bodyIt != pe::LocalBodyIterator::end();
+           ++bodyIt)
+      {
+         bodyIt->translate(real_c(0), real_c(0),
+                           real_c(setup.domainSize[2]) * real_c(0.5) -
+                              (lowestPosition + (highestPosition - lowestPosition) * real_c(0.5)));
+      }
+   }
+   pe::syncShadowOwners< BodyTypeTuple >(*forest, bodyStorageID); // communicate
+
+   // write final packed bed to vtk output
+   vtkWriter->write();
+
+   // write particle positions (relative to particle diameter) to file
+   writePorousGeometry(*forest, bodyStorageID, setup.particleDiameter, setup.porousGeometryFile);
+
+   return EXIT_SUCCESS;
+}
+
+void writePorousGeometry(BlockForest& blockForest, BlockDataID bodyStorageID, uint_t particleDiameter,
+                         const std::string& filename)
+{
+   std::string bodyStats;
+
+   // create file header
+   WALBERLA_ROOT_SECTION() { bodyStats += std::string("x/Dp\t") + std::string("y/Dp\t") + std::string("z/Dp\n"); }
+
+   // write to file from each process
+   for (auto blockIt = blockForest.begin(); blockIt != blockForest.end(); ++blockIt)
+   {
+      for (auto bodyIt = pe::LocalBodyIterator::begin(*blockIt, bodyStorageID); bodyIt != pe::LocalBodyIterator::end();
+           ++bodyIt)
+      {
+         Vector3< real_t > bodyPos = bodyIt->getPosition();
+         bodyPos /= real_c(particleDiameter);
+         bodyStats +=
+            std::to_string(bodyPos[0]) + "\t" + std::to_string(bodyPos[1]) + "\t" + std::to_string(bodyPos[2]) + "\n";
+      }
+   }
+
+   // write text file
+   mpi::writeMPITextFile(filename, bodyStats);
+}
+
+real_t getParticleMaxVel(BlockForest& blockForest, const BlockDataID& bodyStorageID)
+{
+   real_t maxVel = real_c(0);
+
+   for (auto blockIt = blockForest.begin(); blockIt != blockForest.end(); ++blockIt)
+   {
+      for (auto bodyIt = pe::LocalBodyIterator::begin(*blockIt, bodyStorageID); bodyIt != pe::LocalBodyIterator::end();
+           ++bodyIt)
+      {
+         const Vector3< real_t > bodyVel = bodyIt->getLinearVel();
+         real_t bodyVelAbsMax;
+         if (math::abs(bodyVel.max()) > math::abs(bodyVel.min())) { bodyVelAbsMax = math::abs(bodyVel.max()); }
+         else
+         {
+            bodyVelAbsMax = math::abs(bodyVel.min());
+         }
+         if (bodyVelAbsMax > maxVel) { maxVel = bodyVelAbsMax; }
+      }
+   }
+
+   mpi::allReduceInplace< real_t >(maxVel, mpi::MAX);
+   return maxVel;
+}
+} // namespace walberla
+
+int main(int argc, char** argv) { return walberla::main(argc, argv); }
\ No newline at end of file

apps/showcases/PorousMedia/PackedBedCreation.prm

+//======================================================================================================================
+// Parameter, i.e., configuration file for the showcase "PackedBedCreation.cpp".
+//======================================================================================================================
+
+DomainParameters
+{
+   numBlocks < 4, 4, 1 >;
+   particleDiameter 36;
+   relDomainSize < 4, 4, 10 >; // values are multiplied with particleDiameter inside the code
+}
+
+SimulationParameters
+{
+   numInitialParticles 240; // this is not the final number since some particles are removed after they have settled
+   maxTimesteps 10000; // maximum PE timesteps (if convergence is not triggered)
+   convVelocity 5e-2; // velocity at which particles are considered stationary
+}
+
+ContactSolverParameters
+{
+   maxIterations 50;
+   relaxationParameter 0.7;
+   globalLinearAcceleration <0, 0, -0.2>;
+   dt 0.5;
+}
+
+OutputParameters
+{
+   porousGeometryFile packedBedGeometry.txt;
+   vtkInterval 10;
+}
\ No newline at end of file

apps/showcases/PorousMedia/PorousMedia.prm

+//======================================================================================================================
+// Parameter, i.e., configuration file for the showcase "PorousMedia.cpp".
+//======================================================================================================================
+DomainParameters
+{
+   packedBedGeometryFile samplePackedBed.txt; // file containing the positions of particles (relative to their diameter)
+
+   numCoarseBlocks < 4, 4, 20 >; // these blocks are refined on 3 levels (=> actual number of blocks increases)
+   cellsPerDiameter 40;          // on finest level
+   relDomainSize < 4, 4, 20 >;   // values are multiplied with cellsPerDiameter inside the code
+   radiusScale 0.985;            // factor for radially shrinking the particles
+}
+
+SimulationParameters
+{
+   omega 1.98;          // on finest level (omega on coarser levels is larger)
+   Re 150;              // particle Reynolds number
+   maxTimesteps 1000;   // maximum number of time steps to be performed
+   minTimesteps 0;      // minimum number of time steps to be performed; avoids premature convergence detection
+}
+
+OutputParameters
+{
+      // the file names for storing and loading the blockforest and fields are deduced from the setup:
+      // <cellsPerDiameter>_<refinementLevels>_<numCoarseBlocks[0]>_<numCoarseBlocks[1]>_<numCoarseBlocks[2]>.<fileEnding>
+   storeBlockForest false; // fileEnding: ".blockforest"
+   loadBlockForest false;
+
+      // PdfField: field containing the particle distribution functions of a time step
+   storePdfField false;    // fileEnding: ".pdfField"
+   loadPdfField false;
+
+      // AvgField: field containing the time-averaged velocity and density of all time steps
+   storeAvgField false;    // fileEnding: ".avgField"
+   loadAvgField false;
+   avgCounterLoaded 0;     // number of times the average computation was already performed in a loaded AvgField
+
+   fieldStoreInterval 100;  // time step interval for storing the PdfField and AvgField
+
+   vtkFluidField true;           // write the whole fluid field (velocity and density) to vtk output
+   vtkFluidFieldInterval 50;     // time step interval for writing the whole fluid field to vtk output
+   vtkFieldResolution 4;         // scale the fluid field vtk output with 1/<vtkFieldResolution>
+
+   vtkAvgFieldInterval 50;       // write the averaged quantities in the whole to vtk output
+
+   vtkFlagField true;            // write the flag field to vtk output
+   vtkDomainDecomposition true;  // write the domain decomposition to vtk output
+   vtkBodies true;               // write the particle positions to vtk output
+
+      // time step interval in which the pressure drop is computed as difference between avg. pressure of two planes:
+      // 1 diameter above porous medium - 1 diameter below porous medium
+   pressureDropInterval 50;
+
+      // coordinates at which the velocity and density is evaluated; values are multiplied with <cellsPerDiameter> inside
+      // the code and shifted by variable <bedShiftZ> (see PorousMedia.cpp)
+   evalP1 < 2, 2, 10.25 >;
+   evalP2 < 2, 2, 8.1875 >;
+   evalP3 < 2, 2, 5.7 >;
+
+      // time step interval in which the above points are evaluated:
+      // - density and velocities (incl. magnitude) are written to file
+      // - VTK output of xy planes at P1, P2 and P3 is written
+      // - VTK output of xz plane is written
+   evalInterval 10;
+   evalVtk true;     // above mentioned vtk output is written
+
+      // simulation is considered stationary, i.e., converged when the L2 norm of the relative difference between the
+      // current and the former time-averaged density, and velocity of all fluid cells is less than <convThreshold> in
+      // <evalInterval> checks
+   convThreshold 1e-3;
+
+   perfLogInterval 100; // time step interval in which the performance is logged
+}
\ No newline at end of file

apps/showcases/PorousMedia/PorousMediaCumulantLBMKernel.py

+import sympy as sp
+import pystencils as ps
+
+from lbmpy.stencils import get_stencil
+from lbmpy.creationfunctions import create_lb_collision_rule, create_lb_update_rule
+
+from lbmpy_walberla import RefinementScaling, generate_lattice_model
+from pystencils_walberla import CodeGeneration, generate_sweep, generate_pack_info_from_kernel
+
+stencil = get_stencil("D3Q19", ordering="walberla")
+omega = sp.Symbol('omega')
+layout = 'fzyx'
+pdf_field = ps.fields("pdfs(19): [3D]", layout=layout)
+
+optimizations = {'cse_global': True,
+                 'cse_pdfs': False,
+                 'split': True,
+                 'symbolic_field': pdf_field,
+                 'field_layout': layout,
+                 'pre_simplification': True
+                 }
+
+params = {'stencil': stencil,
+          'method': 'cumulant',
+          'relaxation_rate': omega,
+          'equilibrium_order': 4,
+          'maxwellian_moments': True,
+          'compressible': True,
+          }
+
+collision_rule = create_lb_collision_rule(optimization=optimizations, **params)
+update_rule = create_lb_update_rule(collision_rule=collision_rule, optimization=optimizations)
+
+refinement_scaling = RefinementScaling()
+refinement_scaling.add_standard_relaxation_rate_scaling(omega)
+
+with CodeGeneration() as ctx:
+   generate_lattice_model(ctx, "LbCodeGen_LatticeModel", collision_rule, refinement_scaling=refinement_scaling,
+                          field_layout=layout)

apps/showcases/PorousMedia/samplePackedBed.txt

+x/Dp	y/Dp	z/Dp
+1.153859	0.009232	7.504831
+0.547144	0.196281	9.091072
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