[shallowwater] add friction law with no friciton

dumux/material/fluidmatrixinteractions/frictionlaws/CMakeLists.txt

@@ -2,4 +2,5 @@ install(FILES
 frictionlaw.hh
 manning.hh
 nikuradse.hh
+nofriction.hh
 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dumux/material/fluidmatrixinteractions/frictionlaws)

dumux/material/fluidmatrixinteractions/frictionlaws/nofriction.hh

+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+/*****************************************************************************
+ *   See the file COPYING for full copying permissions.                      *
+ *                                                                           *
+ *   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 3 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, see <http://www.gnu.org/licenses/>.   *
+ *****************************************************************************/
+/*!
+ * \file
+ * \ingroup Fluidmatrixinteractions
+ * \copydoc Dumux::FrictionLawNoFriction
+ */
+#ifndef DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_NOFRICTION_HH
+#define DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_NOFRICTION_HH
+
+#include "frictionlaw.hh"
+
+namespace Dumux {
+
+/*!
+ * \ingroup Fluidmatrixinteractions
+ * \brief A pseudo friction law with no bottom friction
+ */
+template <typename VolumeVariables>
+class FrictionLawNoFriction : public FrictionLaw<VolumeVariables>
+{
+    using Scalar = typename VolumeVariables::PrimaryVariables::value_type;
+public:
+    /*!
+     * \brief Constructor
+     */
+    FrictionLawNoFriction() = default;
+
+    /*!
+     * \brief Compute the shear stress.
+     *
+     * \param volVars Volume variables
+     *
+     * Compute the shear stress due to friction. The shear stress is not a tensor as know
+     * from contiuums mechanics, but a force projected on an area. Therefore it is a
+     * vector with two entries. For this law without friction, the shearStress is zero.
+     *
+     * \return shear stress [N/m^2]. First entry is the x-component, the second the y-component.
+     */
+    Dune::FieldVector<Scalar, 2> shearStress(const VolumeVariables& volVars) const final
+    {
+        return {0.0, 0.0};
+    }
+};
+
+} // end namespace Dumux
+
+#endif