[ff][ns] Implement class for slip conditions

dumux/freeflow/navierstokes/slipcondition.hh

+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+//
+// SPDX-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+/*!
+ * \file
+ * \ingroup NavierStokesModel
+ * \brief Navier Stokes slip condition
+ */
+#ifndef DUMUX_NAVIERSTOKES_SLIPCONDITION_HH
+#define DUMUX_NAVIERSTOKES_SLIPCONDITION_HH
+
+#include <dumux/discretization/method.hh>
+
+namespace Dumux {
+
+namespace SlipConditions {
+
+struct BJ : public Utility::Tag<BJ> {
+    static std::string name() { return "Beavers-Joseph"; }
+};
+
+inline constexpr BJ bj{};
+
+} // end namespace SlipModel
+
+template<class GridGeometry, class SlipCondition>
+class SlipVelocityHelper;
+
+/*!
+ * \ingroup NavierStokesModel
+ * \brief Navier Stokes slip velocity helper
+ */
+template<class GridGeometry>
+class SlipVelocityHelper<GridGeometry, SlipConditions::BJ>
+{
+    using GridView = typename GridGeometry::GridView;
+    using Element = typename GridView::template Codim<0>::Entity;
+
+    using FVElementGeometry = typename GridGeometry::LocalView;
+    using SubControlVolume = typename FVElementGeometry::SubControlVolume;
+    using SubControlVolumeFace = typename FVElementGeometry::SubControlVolumeFace;
+
+    static constexpr int dimWorld = GridView::dimensionworld;
+    using Scalar = typename GridView::ctype;
+    using Vector = Dune::FieldVector<Scalar, dimWorld>;
+
+public:
+    template<class Problem, class ElementVolumeVariables>
+    static Vector velocity(const Problem& problem,
+                           const FVElementGeometry& fvGeometry,
+                           const SubControlVolumeFace& scvf,
+                           const ElementVolumeVariables& elemVolVars,
+                           Scalar tangentialVelocityGradient)
+   {
+        if constexpr (GridGeometry::discMethod == DiscretizationMethods::fcstaggered)
+        {
+            assert(scvf.isLateral());
+            assert(scvf.boundary());
+
+            const auto& scv = fvGeometry.scv(scvf.insideScvIdx());
+
+            // create a unit normal vector oriented in positive coordinate direction
+            Vector tangent(0.0);
+            tangent[scv.dofAxis()] = 1.0;
+
+            // du/dy + dv/dx = beta * (u_boundary-uPM)
+            // beta = alpha/sqrt(K)
+            const Scalar betaBJ = problem.betaBJ(fvGeometry, scvf, tangent);
+            const Scalar distanceNormalToBoundary = (scvf.ipGlobal() - scv.dofPosition()).two_norm();
+
+            static const bool onlyNormalGradient = getParamFromGroup<bool>(problem.paramGroup(), "FreeFlow.EnableUnsymmetrizedVelocityGradientForBeaversJoseph", false);
+            if (onlyNormalGradient)
+                tangentialVelocityGradient = 0.0;
+
+            const auto& porousMediumVelocity = problem.porousMediumVelocity(fvGeometry, scvf);
+            const Scalar scalarSlipVelocity = (tangentialVelocityGradient*distanceNormalToBoundary
+                + porousMediumVelocity * tangent * betaBJ * distanceNormalToBoundary
+                + elemVolVars[scv].velocity()) / (betaBJ*distanceNormalToBoundary + 1.0);
+
+            return scalarSlipVelocity*tangent;
+        }
+        else
+            DUNE_THROW(Dune::NotImplemented, "Slip velocity currently only implemented for fcstaggered");
+    }
+};
+
+
+} // end namespace Dumux
+
+#endif