zeroGradientLatticePostProcessor3D.h

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/*  This file is part of the OpenLB library
 *
 *  Copyright (C) 2023 Fedor Bukreev, Adrian Kummerländer
 *  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
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 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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*/
 
#ifndef ZERO_GRADIENT_LATTICE_POST_PROCESSOR_3D_H
#define ZERO_GRADIENT_LATTICE_POST_PROCESSOR_3D_H
 
#include "core/blockStructure.h"
#include "core/postProcessing.h"
#include "core/util.h"
#include "dynamics/latticeDescriptors.h"
#include "utilities/omath.h"
 
 
namespace olb {
 
//======================================================================
// ======== Zero Gradient Boundary for AD 3D ======//
//======================================================================
template<typename T, typename DESCRIPTOR>
struct zeroGradientLatticePostProcessor3D
{
  static constexpr OperatorScope scope = OperatorScope::PerCell;
 
  int getPriority() const {
    return 0;
  }
 
template <typename CELL>
void apply(CELL& cell) any_platform{
  for(int iPop = 0; iPop<DESCRIPTOR::q; iPop++){
    const auto c = descriptors::c<DESCRIPTOR>(iPop);
    T v = T{0.};
    T fluidN = cell.neighbor({c[0], c[1], c[2]}).template getField<descriptors::NEIGHBOR>();
    T fluidNN = cell.neighbor({2*c[0], 2*c[1], 2*c[2]}).template getField<descriptors::NEIGHBOR>();
    v = fluidN * cell.neighbor({c[0], c[1], c[2]})[iPop] + fluidN * fluidNN * cell.neighbor({2*c[0], 2*c[1], 2*c[2]})[iPop];
    v *= (fluidN - T{0.5} * fluidN * fluidNN);
    cell[iPop] = v;
  }
}
};
}
 
#endif