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/* This file is part of the OpenLB library
*
* Copyright (C) 2006, 2007 Jonas Latt
* 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.
*/
/** \file
* Efficient 2D specializations for lbHelpersD2Q9.h
*/
#ifndef FIRST_ORDER_LB_HELPERS_2D_H
#define FIRST_ORDER_LB_HELPERS_2D_H
namespace olb {
/// Compute Pi tensor efficiently on D2Q9 lattice
namespace neqPiD2Q9 {
using namespace olb::util::tensorIndices2D;
template<typename T>
T fromPiToFneq0(const T pi[3])
{
return (T)2 * (-(T)1/(T)3*pi[xx] - (T)1/(T)3*pi[yy]);
}
template<typename T>
T fromPiToFneq1(const T pi[3])
{
return (T)1/(T)4 * ((T)1/(T)3*pi[xx] + (T)1/(T)3*pi[yy] - pi[xy]);
}
template<typename T>
T fromPiToFneq2(const T pi[3])
{
return (T)1/(T)2 * ((T)2/(T)3*pi[xx] - (T)1/(T)3*pi[yy]);
}
template<typename T>
T fromPiToFneq3(const T pi[3])
{
return (T)1/(T)4 * ((T)1/(T)3*pi[xx] + (T)1/(T)3*pi[yy] + pi[xy]);
}
template<typename T>
T fromPiToFneq4(const T pi[3])
{
return (T)1/(T)2 * (-(T)1/(T)3*pi[xx] + (T)2/(T)3*pi[yy]);
}
} // namespace neqPiD2Q9
template<typename T>
struct rlbHelpers<T, descriptors::D2Q9<>> {
static T rlbCollision (
Cell<T,descriptors::D2Q9<>>& cell,
T rho, const T u[2], const T pi[3], T omega )
{
typedef lbHelpers<T, descriptors::D2Q9<>> LH;
const T uSqr = u[0]*u[0] + u[1]*u[1];
cell[0] = LH::equilibrium(0, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq0(pi);
cell[1] = LH::equilibrium(1, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq1(pi);
cell[2] = LH::equilibrium(2, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq2(pi);
cell[3] = LH::equilibrium(3, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq3(pi);
cell[4] = LH::equilibrium(4, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq4(pi);
cell[5] = LH::equilibrium(5, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq1(pi);
cell[6] = LH::equilibrium(6, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq2(pi);
cell[7] = LH::equilibrium(7, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq3(pi);
cell[8] = LH::equilibrium(8, rho, u, uSqr) +
((T)1-omega) * neqPiD2Q9::fromPiToFneq4(pi);
return uSqr;
}
}; // struct rlbHelpers<D2Q9<>>
} // namespace olb
#endif
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