From 94d3e79a8617f88dc0219cfdeedfa3147833719d Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Mon, 24 Jun 2019 14:43:36 +0200
Subject: Initialize at openlb-1-3

---
 src/core/finiteDifference2D.h | 141 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 src/core/finiteDifference2D.h

(limited to 'src/core/finiteDifference2D.h')

diff --git a/src/core/finiteDifference2D.h b/src/core/finiteDifference2D.h
new file mode 100644
index 0000000..a6e0938
--- /dev/null
+++ b/src/core/finiteDifference2D.h
@@ -0,0 +1,141 @@
+/*  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.
+*/
+
+#ifndef FINITE_DIFFERENCE_2D_H
+#define FINITE_DIFFERENCE_2D_H
+
+#include "finiteDifference.h"
+
+namespace olb {
+
+namespace fd {
+
+template<typename T, typename DESCRIPTOR,
+         int direction, int orientation,
+         bool orthogonal>
+struct DirectedGradients2D {
+  static void interpolateVector(T velDeriv[DESCRIPTOR::d],
+                                BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                int iX, int iY);
+  static void interpolateScalar(T& rhoDeriv,
+                                BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                int iX, int iY);
+};
+
+// Implementation for orthogonal==true; i.e. the derivative is along
+// the boundary normal.
+template<typename T, typename DESCRIPTOR,
+         int direction, int orientation>
+struct DirectedGradients2D<T, DESCRIPTOR, direction, orientation, true> {
+  static void interpolateVector(T velDeriv[DESCRIPTOR::d],
+                                BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                int iX, int iY)
+  {
+    using namespace fd;
+
+    T u0[DESCRIPTOR::d], u1[DESCRIPTOR::d], u2[DESCRIPTOR::d];
+
+    blockLattice.get(iX,iY).computeU(u0);
+    blockLattice.get (
+      iX+(direction==0 ? (-orientation):0),
+      iY+(direction==1 ? (-orientation):0) ).computeU(u1);
+    blockLattice.get (
+      iX+(direction==0 ? (-2*orientation):0),
+      iY+(direction==1 ? (-2*orientation):0) ).computeU(u2);
+
+    for (int iD=0; iD<DESCRIPTOR::d; ++iD) {
+      velDeriv[iD] = -orientation * boundaryGradient(u0[iD], u1[iD], u2[iD]);
+    }
+  }
+
+  static void interpolateScalar(T& rhoDeriv,
+                                BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                int iX, int iY)
+  {
+    using namespace fd;
+
+    T rho0 = blockLattice.get(iX,iY).computeRho();
+    T rho1 = blockLattice.get (
+               iX+(direction==0 ? (-orientation):0),
+               iY+(direction==1 ? (-orientation):0) ).computeRho();
+    T rho2 = blockLattice.get (
+               iX+(direction==0 ? (-2*orientation):0),
+               iY+(direction==1 ? (-2*orientation):0) ).computeRho();
+
+    rhoDeriv = -orientation * boundaryGradient(rho0, rho1, rho2);
+
+  }
+};
+
+
+// Implementation for orthogonal==false; i.e. the derivative is aligned
+// with the boundary.
+template<typename T, typename DESCRIPTOR,
+         int direction, int orientation>
+struct DirectedGradients2D<T, DESCRIPTOR, direction, orientation, false> {
+  static void interpolateVector(T velDeriv[DESCRIPTOR::d],
+                                BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                int iX, int iY)
+  {
+    using namespace fd;
+
+    T u_p1[DESCRIPTOR::d], u_m1[DESCRIPTOR::d];
+
+    int deriveDirection = 1-direction;
+    blockLattice.get (
+      iX+(deriveDirection==0 ? 1:0),
+      iY+(deriveDirection==1 ? 1:0) ).computeU(u_p1);
+    blockLattice.get (
+      iX+(deriveDirection==0 ? (-1):0),
+      iY+(deriveDirection==1 ? (-1):0) ).computeU(u_m1);
+
+    for (int iD=0; iD<DESCRIPTOR::d; ++iD) {
+      velDeriv[iD] = fd::centralGradient(u_p1[iD],u_m1[iD]);
+    }
+  }
+
+  static void  interpolateScalar(T& rhoDeriv,
+                                 BlockLattice2D<T,DESCRIPTOR> const& blockLattice,
+                                 int iX, int iY)
+  {
+    using namespace fd;
+
+    int deriveDirection = 1-direction;
+    T rho_p1 = blockLattice.get (
+                 iX+(deriveDirection==0 ? 1:0),
+                 iY+(deriveDirection==1 ? 1:0) ).computeRho();
+    T rho_m1 = blockLattice.get (
+                 iX+(deriveDirection==0 ? (-1):0),
+                 iY+(deriveDirection==1 ? (-1):0) ).computeRho();
+
+    rhoDeriv = centralGradient(rho_p1, rho_m1);
+
+  }
+};
+
+}  // namespace fd
+
+}  // namespace olb
+
+
+#endif
-- 
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