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+/*  This file is part of the OpenLB library
+ *
+ *  Copyright (C) 2006, 2007, 2017 Orestis Malaspinas, Jonas Latt, Mathias J. Krause
+ *  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 entropic dynamics classes (e.g. EntropicEq,
+ * ForcedEntropicEq, Entropic, ForcedEntropic) with which a Cell object
+ * can be instantiated -- header file.
+ *
+ * Entropic Modell:
+ * Ansumali, Santosh, Iliya V. Karlin, and Hans Christian Öttinger
+ * Minimal entropic kinetic models for hydrodynamics
+ * EPL (Europhysics Letters) 63.6 (2003): 798
+ */
+
+#ifndef ENTROPIC_LB_DYNAMICS_H
+#define ENTROPIC_LB_DYNAMICS_H
+
+#include "dynamics/dynamics.h"
+
+namespace olb {
+
+template<typename T, typename DESCRIPTOR> class Cell;
+
+
+/// Implementation of the entropic collision step
+template<typename T, typename DESCRIPTOR>
+class EntropicEqDynamics : public BasicDynamics<T,DESCRIPTOR> {
+public:
+  /// Constructor
+  EntropicEqDynamics(T omega_, Momenta<T,DESCRIPTOR>& momenta_);
+  /// Compute equilibrium distribution function
+  T computeEquilibrium(int iPop, T rho, const T u[DESCRIPTOR::d], T uSqr) const override;
+  /// Collision step
+  void collide(Cell<T,DESCRIPTOR>& cell,
+                       LatticeStatistics<T>& statistics_) override;
+  /// Get local relaxation parameter of the dynamics
+  T getOmega() const override;
+  /// Set local relaxation parameter of the dynamics
+  void setOmega(T omega_) override;
+private:
+  T omega;  ///< relaxation parameter
+};
+
+/// Implementation of the forced entropic collision step
+template<typename T, typename DESCRIPTOR>
+class ForcedEntropicEqDynamics : public BasicDynamics<T,DESCRIPTOR> {
+public:
+  /// Constructor
+  ForcedEntropicEqDynamics(T omega_, Momenta<T,DESCRIPTOR>& momenta_);
+  /// Compute equilibrium distribution function
+  virtual T computeEquilibrium(int iPop, T rho, const T u[DESCRIPTOR::d], T uSqr) const;
+  /// Collision step
+  virtual void collide(Cell<T,DESCRIPTOR>& cell,
+                       LatticeStatistics<T>& statistics_);
+  /// Get local relaxation parameter of the dynamics
+  virtual T getOmega() const;
+  /// Set local relaxation parameter of the dynamics
+  virtual void setOmega(T omega_);
+private:
+  T omega;  ///< relaxation parameter
+};
+
+/// Implementation of the entropic collision step
+
+template<typename T, typename DESCRIPTOR>
+class EntropicDynamics : public BasicDynamics<T,DESCRIPTOR> {
+public:
+  /// Constructor
+  EntropicDynamics(T omega_, Momenta<T,DESCRIPTOR>& momenta_);
+  /// Compute equilibrium distribution function
+  T computeEquilibrium(int iPop, T rho, const T u[DESCRIPTOR::d], T uSqr) const override;
+  /// Collision step
+  void collide(Cell<T,DESCRIPTOR>& cell,
+                       LatticeStatistics<T>& statistics_) override;
+  /// Get local relaxation parameter of the dynamics
+  T getOmega() const override;
+  /// Set local relaxation parameter of the dynamics
+  void setOmega(T omega_) override;
+private:
+  /// computes the entropy function H(f)=sum_i f_i*ln(f_i/t_i)
+  T computeEntropy(const T f[]);
+  /// computes the entropy growth H(f)-H(f-alpha*fNeq)
+  T computeEntropyGrowth(const T f[], const T fNeq[], const T &alpha);
+  /// computes the entropy growth derivative
+  /// dH/dalpha=-sum_i fNeq_i*ln((f_i-alpha*fNeq_i)/t_i)
+  T computeEntropyGrowthDerivative(const T f[], const T fNeq[], const T &alpha);
+  /// Get the alpha parameter
+  bool getAlpha(T &alpha, const T f[], const T fNeq[]);
+
+  T omega;  ///< relaxation parameter
+};
+
+/// Implementation of the forced entropic collision step
+template<typename T, typename DESCRIPTOR>
+class ForcedEntropicDynamics : public BasicDynamics<T,DESCRIPTOR> {
+public:
+  /// Constructor
+  ForcedEntropicDynamics(T omega_, Momenta<T,DESCRIPTOR>& momenta_);
+  /// Compute equilibrium distribution function
+  virtual T computeEquilibrium(int iPop, T rho, const T u[DESCRIPTOR::d], T uSqr) const;
+  /// Collision step
+  virtual void collide(Cell<T,DESCRIPTOR>& cell,
+                       LatticeStatistics<T>& statistics_);
+  /// Get local relaxation parameter of the dynamics
+  virtual T getOmega() const;
+  /// Set local relaxation parameter of the dynamics
+  virtual void setOmega(T omega_);
+private:
+  /// computes the entropy function H(f)=sum_i f_i*ln(f_i/t_i)
+  T computeEntropy(const T f[]);
+  /// computes the entropy growth H(f)-H(f-alpha*fNeq)
+  T computeEntropyGrowth(const T f[], const T fNeq[], const T &alpha);
+  /// computes the entropy growth derivative
+  /// dH/dalpha=-sum_i fNeq_i*ln((f_i-alpha*fNeq_i)/t_i)
+  T computeEntropyGrowthDerivative(const T f[], const T fNeq[], const T &alpha);
+  /// Get the alpha parameter
+  bool getAlpha(T &alpha, const T f[], const T fNeq[]);
+
+  T omega;  ///< relaxation parameter
+};
+}
+
+#endif