partialSlip2D.hh

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/*  This file is part of the OpenLB library
 *
 *  Copyright (C) 2024 Fedor Bukreev, Dennis Teutscher, Alexander Schulz
 *  E-mail contact: info@openlb.net
 *  The most recent release of OpenLB can be downloaded at
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//This file contains the Partial Slip Boundary
//This is an onLattice boundary
//This is a new version of the Boundary, which only contains free floating functions
 
#ifndef PARTIAL_SLIP_2D_HH
#define PARTIAL_SLIP_2D_HH
 
#include "partialSlip2D.h"
 
namespace olb {
 
namespace boundary {
 
template <int NX, int NY>
struct PartialSlipO2D {
  static constexpr OperatorScope scope = OperatorScope::PerCellWithParameters;
 
  int getPriority() const {
    return -1;
  }
 
  using parameters = typename meta::list<descriptors::TUNER>;
 
 
  template <typename CELL, typename PARAMETERS, typename V = typename CELL::value_t>
  void apply(CELL& x_b, PARAMETERS& parameters) any_platform {
    using DESCRIPTOR = typename CELL::descriptor_t;
    const V tuner = parameters.template get<descriptors::TUNER>();
    int reflectionPop[DESCRIPTOR::q];
    int mirrorDirection0;
    int mirrorDirection1;
    int mult = 2 / (NX*NX + NY*NY);
    reflectionPop[0] =0;
    for (int iPop = 1; iPop < DESCRIPTOR::q; iPop++) {
      reflectionPop[iPop] = 0;
      // iPop are the directions which pointing into the fluid, discreteNormal is pointing outwarts
      int scalarProduct = descriptors::c<DESCRIPTOR>(iPop,0)*NX + descriptors::c<DESCRIPTOR>(iPop,1)*NY;
      if ( scalarProduct < 0) {
        // bounce back for the case discreteNormalX = discreteNormalY = 1, that is mult=1
        if (mult == 1) {
          mirrorDirection0 = -descriptors::c<DESCRIPTOR>(iPop,0);
          mirrorDirection1 = -descriptors::c<DESCRIPTOR>(iPop,1);
        }
        else {
          mirrorDirection0 = descriptors::c<DESCRIPTOR>(iPop,0) - mult*scalarProduct*NX;
          mirrorDirection1 = descriptors::c<DESCRIPTOR>(iPop,1) - mult*scalarProduct*NY;
        }
 
        // run through all lattice directions and look for match of direction
        for (int i = 1; i < DESCRIPTOR::q; i++) {
          if (descriptors::c<DESCRIPTOR>(i,0)==mirrorDirection0
              && descriptors::c<DESCRIPTOR>(i,1)==mirrorDirection1) {
            reflectionPop[iPop] = i;
            break;
          }
        }
      }
    }
    for (int iPop = 1; iPop < DESCRIPTOR::q ; ++iPop) {
      if (reflectionPop[iPop]!=0) {
        //do reflection
        x_b[iPop] = tuner*x_b[reflectionPop[iPop]];
      }
    }
    for (int iPop = 1; iPop < DESCRIPTOR::q/2 ; ++iPop) {
      V provv = x_b[descriptors::opposite<DESCRIPTOR>(iPop)];
      x_b[descriptors::opposite<DESCRIPTOR>(iPop)] += (1.-tuner)*x_b[iPop];
      x_b[iPop] += (1.-tuner)*provv;
    }
  }
 
};
 
}
 
}
 
#endif