path: root/examples/laminar/cylinder2d/cylinder2d.cpp

/*  Lattice Boltzmann sample, written in C++, using the OpenLB
 *  library
 *
 *  Copyright (C) 2006-2014 Jonas Latt, Mathias J. Krause,
 *  Vojtech Cvrcek, Peter Weisbrod
 *  E-mail contact: info@openlb.net
 *  The most recent release of OpenLB can be downloaded at
 *  <http://www.openlb.net/>
 *
 *  This program 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 2
 *  of the License, or (at your option) any later version.
 *
 *  This program 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 this program; if not, write to the Free
 *  Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA  02110-1301, USA.
 */

/* cylinder2d.cpp:
 * This example examines a steady flow past a cylinder placed in a channel.
 * The cylinder is offset somewhat from the center of the flow to make the
 * steady-state symmetrical flow unstable. At the inlet, a Poiseuille profile is
 * imposed on the velocity, whereas the outlet implements a Dirichlet pressure
 * condition set by p = 0.
 * Inspired by "Benchmark Computations of Laminar Flow Around
 * a Cylinder" by M.Schäfer and S.Turek. For high resolution, low
 * latticeU, and enough time to converge, the results for pressure drop, drag
 * and lift lie within the estimated intervals for the exact results.
 * An unsteady flow with Karman vortex street can be created by changing the
 * Reynolds number to Re=100.
 */


#include "olb2D.h"
#ifndef OLB_PRECOMPILED // Unless precompiled version is used,
#include "olb2D.hh"   // include full template code
#endif
#include <vector>
#include <cmath>
#include <iostream>
#include <fstream>

using namespace olb;
using namespace olb::descriptors;
using namespace olb::graphics;
using namespace olb::util;
using namespace std;

typedef double T;
#define DESCRIPTOR D2Q9<>


// Parameters for the simulation setup
const int N = 10;       // resolution of the model
const T Re = 20.;       // Reynolds number
const T maxPhysT = 16.; // max. simulation time in s, SI unit
const T L = 0.1/N;      // latticeL
const T lengthX = 2.2;
const T lengthY = .41+L;
const T centerCylinderX = 0.2;
const T centerCylinderY = 0.2+L/2.;
const T radiusCylinder = 0.05;


// Stores geometry information in form of material numbers
void prepareGeometry( UnitConverter<T, DESCRIPTOR> const& converter,
                      SuperGeometry2D<T>& superGeometry )
{

  OstreamManager clout( std::cout,"prepareGeometry" );
  clout << "Prepare Geometry ..." << std::endl;

  Vector<T,2> extend( lengthX,lengthY );
  Vector<T,2> center( centerCylinderX,centerCylinderY );
  Vector<T,2> origin;
  IndicatorCircle2D<T> circle( center, radiusCylinder );

  superGeometry.rename( 0,2 );

  superGeometry.rename( 2,1,1,1 );

  // Set material number for inflow
  extend[0] = 2.*L;
  origin[0] = -L;
  IndicatorCuboid2D<T> inflow( extend, origin );
  superGeometry.rename( 2,3,1,inflow );
  // Set material number for outflow
  origin[0] = lengthX-L;
  IndicatorCuboid2D<T> outflow( extend, origin );
  superGeometry.rename( 2,4,1,outflow );
  // Set material number for cylinder
  superGeometry.rename( 1,5,circle );

  // Removes all not needed boundary voxels outside the surface
  superGeometry.clean();
  superGeometry.checkForErrors();

  superGeometry.print();

  clout << "Prepare Geometry ... OK" << std::endl;
}

// Set up the geometry of the simulation
void prepareLattice( SuperLattice2D<T,DESCRIPTOR>& sLattice,
                     UnitConverter<T, DESCRIPTOR> const& converter,
                     Dynamics<T, DESCRIPTOR>& bulkDynamics,
                     sOnLatticeBoundaryCondition2D<T,DESCRIPTOR>& sBoundaryCondition,
                     sOffLatticeBoundaryCondition2D<T,DESCRIPTOR>& offBc,
                     SuperGeometry2D<T>& superGeometry )
{

  OstreamManager clout( std::cout,"prepareLattice" );
  clout << "Prepare Lattice ..." << std::endl;

  const T omega = converter.getLatticeRelaxationFrequency();

  // Material=0 -->do nothing
  sLattice.defineDynamics( superGeometry, 0, &instances::getNoDynamics<T, DESCRIPTOR>() );

  // Material=1 -->bulk dynamics
  // Material=3 -->bulk dynamics (inflow)
  // Material=4 -->bulk dynamics (outflow)
  auto bulkIndicator = superGeometry.getMaterialIndicator({1, 3, 4});
  sLattice.defineDynamics( bulkIndicator, &bulkDynamics );

  // Material=2 -->bounce back
  sLattice.defineDynamics( superGeometry, 2, &instances::getBounceBack<T, DESCRIPTOR>() );

  // Setting of the boundary conditions
  sBoundaryCondition.addVelocityBoundary( superGeometry, 3, omega );
  sBoundaryCondition.addPressureBoundary( superGeometry, 4, omega );

  // Material=5 -->bounce back
  //sLattice.defineDynamics(superGeometry, 5, &instances::getBounceBack<T, DESCRIPTOR>());

  // Material=5 -->bouzidi

  Vector<T,2> center( centerCylinderX,centerCylinderY );
  IndicatorCircle2D<T> circle( center, radiusCylinder );

  sLattice.defineDynamics( superGeometry, 5, &instances::getNoDynamics<T,DESCRIPTOR>() );
  offBc.addZeroVelocityBoundary( superGeometry, 5, circle );

  // Initial conditions
  AnalyticalConst2D<T,T> rhoF( 1 );
  std::vector<T> velocity( 2,T( 0 ) );
  AnalyticalConst2D<T,T> uF( velocity );

  // Initialize all values of distribution functions to their local equilibrium
  sLattice.defineRhoU( bulkIndicator, rhoF, uF );
  sLattice.iniEquilibrium( bulkIndicator, rhoF, uF );

  // Make the lattice ready for simulation
  sLattice.initialize();

  clout << "Prepare Lattice ... OK" << std::endl;
}

// Generates a slowly increasing inflow for the first iTMaxStart timesteps
void setBoundaryValues( SuperLattice2D<T, DESCRIPTOR>& sLattice,
                        UnitConverter<T, DESCRIPTOR> const& converter, int iT,
                        SuperGeometry2D<T>& superGeometry )
{

  OstreamManager clout( std::cout,"setBoundaryValues" );

  // No of time steps for smooth start-up
  int iTmaxStart = converter.getLatticeTime( maxPhysT*0.4 );
  int iTupdate = 5;

  if ( iT%iTupdate==0 && iT<= iTmaxStart ) {
    // Smooth start curve, sinus
    // SinusStartScale<T,int> StartScale(iTmaxStart, T(1));

    // Smooth start curve, polynomial
    PolynomialStartScale<T,T> StartScale( iTmaxStart, T( 1 ) );

    // Creates and sets the Poiseuille inflow profile using functors
    T iTvec[1] = {T( iT )};
    T frac[1] = {};
    StartScale( frac,iTvec );
    T maxVelocity = converter.getCharLatticeVelocity()*3./2.*frac[0];
    T distance2Wall = L/2.;
    Poiseuille2D<T> poiseuilleU( superGeometry, 3, maxVelocity, distance2Wall );

    sLattice.defineU( superGeometry, 3, poiseuilleU );
  }

}

// Computes the pressure drop between the voxels before and after the cylinder
void getResults( SuperLattice2D<T, DESCRIPTOR>& sLattice,
                 UnitConverter<T, DESCRIPTOR> const& converter, int iT,
                 SuperGeometry2D<T>& superGeometry, Timer<T>& timer,
                 CircularBuffer<T>& buffer )
{

  OstreamManager clout( std::cout,"getResults" );

  SuperVTMwriter2D<T> vtmWriter( "cylinder2d" );
  SuperLatticePhysVelocity2D<T, DESCRIPTOR> velocity( sLattice, converter );
  SuperLatticePhysPressure2D<T, DESCRIPTOR> pressure( sLattice, converter );
  vtmWriter.addFunctor( velocity );
  vtmWriter.addFunctor( pressure );

  const int vtkIter  = converter.getLatticeTime( .3 );
  const int statIter = converter.getLatticeTime( .1 );

  T point[2] = {};
  point[0] = centerCylinderX + 3*radiusCylinder;
  point[1] = centerCylinderY;
  AnalyticalFfromSuperF2D<T> intpolateP( pressure, true );
  T p;
  intpolateP( &p,point );
  buffer.insert(p);

  if ( iT == 0 ) {
    // Writes the geometry, cuboid no. and rank no. as vti file for visualization
    SuperLatticeGeometry2D<T, DESCRIPTOR> geometry( sLattice, superGeometry );
    SuperLatticeCuboid2D<T, DESCRIPTOR> cuboid( sLattice );
    SuperLatticeRank2D<T, DESCRIPTOR> rank( sLattice );
    vtmWriter.write( geometry );
    vtmWriter.write( cuboid );
    vtmWriter.write( rank );

    vtmWriter.createMasterFile();
  }

  // Writes the vtk files
  if ( iT%vtkIter == 0 && iT > 0 ) {
    vtmWriter.write( iT );