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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
* A collection of dynamics classes (e.g. BGK) with which a Cell object
* can be instantiated -- header file.
*/
#ifndef ENTROPIC_LB_HELPERS_H
#define ENTROPIC_LB_HELPERS_H
#include <cmath>
namespace olb {
template<typename T, typename DESCRIPTOR>
struct entropicLbHelpers {
/// Computation of equilibrium distribution
static T equilibrium( int iPop, T rho, const T u[DESCRIPTOR::d])
{
typedef DESCRIPTOR L;
const T invCs = sqrt(descriptors::invCs2<T,L>());
const T sqt3 = sqrt(3.0);
T prod = (T)1;
for (int iD=0; iD < DESCRIPTOR::d; ++iD) {
T uc = u[iD] * invCs; // u[iD] / c_s
prod *= ((T)2 - sqrt(1.0+uc*uc)) *
pow((2.0 / sqt3 * uc +
sqrt(1.0+uc*uc))/(1.0-uc/sqt3),
descriptors::c<L>(iPop,iD)/sqt3*invCs);
}
return rho*descriptors::t<T,L>(iPop)*prod-descriptors::t<T,L>(iPop);
}
/// Computation of equilibrium distribution
static T equilibriumApprox( int iPop, T rho, const T u[DESCRIPTOR::d])
{
typedef DESCRIPTOR L;
T uSqr = util::normSqr<T,L::d>(u);
T cu = T();
for (int iD=0; iD < DESCRIPTOR::d; ++iD) {
cu += descriptors::c<L>(iPop,iD)*u[iD];
}
return rho * descriptors::t<T,L>(iPop) * (1.0 +
cu*descriptors::invCs2<T,L>() - 0.5 * uSqr*descriptors::invCs2<T,L>() + 0.5*pow(descriptors::invCs2<T,L>(),2)*cu*cu
- 0.5*pow(descriptors::invCs2<T,L>(),2)*cu*uSqr + pow(cu,3)*pow(descriptors::invCs2<T,L>(),3)/6.0
+ 0.125*uSqr*uSqr*pow(descriptors::invCs2<T,L>(),2) - 0.25*cu*cu*uSqr*pow(descriptors::invCs2<T,L>(),3)
+ pow(cu,4)*pow(descriptors::invCs2<T,L>(),4)/24.0)-descriptors::t<T,L>(iPop);
}
};
}
#include "entropicLbHelpers2D.h"
#include "entropicLbHelpers3D.h"
#endif
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