Added basic fluidized bed showcase, demonstrating the fluid-particle /...

Added basic fluidized bed showcase, demonstrating the fluid-particle / lbm-mesapd coupling functionalities for an application

apps/showcases/CMakeLists.txt

 add_subdirectory( BidisperseFluidizedBed )
 add_subdirectory( CombinedResolvedUnresolved )
+add_subdirectory( FluidizedBed )
 add_subdirectory( HeatConduction )
 add_subdirectory( Mixer )
 add_subdirectory( PegIntoSphereBed )

apps/showcases/FluidizedBed/CMakeLists.txt

+waLBerla_link_files_to_builddir( "*.prm" )
+
+waLBerla_add_executable ( NAME FluidizedBed FILES FluidizedBed.cpp
+                          DEPENDS blockforest boundary core domain_decomposition field lbm lbm_mesapd_coupling mesa_pd postprocessing timeloop vtk )

apps/showcases/FluidizedBed/input.prm

+PhysicalSetup // all to be specified in SI units!
+{
+    xSize 0.05; // = width
+    ySize 0.02; // = depth
+    zSize 0.10; // = height
+
+    periodicInX true;
+    periodicInY true;
+
+    runtime 10.0;
+
+    uInflow 0.01;
+    gravitationalAcceleration 9.81;
+
+    kinematicViscosityFluid 1e-5;
+    densityFluid 1000.;
+
+    particleDiameter 0.002;
+    densityParticle 1100.;
+    dynamicFrictionCoefficient 0.15;
+    coefficientOfRestitution 0.6;
+
+    particleGenerationSpacing 0.00401;
+}
+
+NumericalSetup
+{
+    dx 0.0002; // in m
+    uInflow 0.01; // in LBM units, should be smaller than 0.1, this then determines dt
+
+    // product of number of blocks should be equal to number of used processes
+    numXBlocks 2;
+    numYBlocks 2;
+    numZBlocks 2;
+
+    useLubricationForces true;
+    numberOfParticleSubCycles 10;
+}
+
+Output
+{
+    infoSpacing 0.01; // in s
+
+    vtkSpacingParticles 0.1; // in s
+    vtkSpacingFluid 0.1; // in s
+    vtkFolder vtk_out;
+}