cs_gradient_boundary.h

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#ifndef CS_GRADIENT_BOUNDARY_H
#define CS_GRADIENT_BOUNDARY_H
 
/*============================================================================
 * Gradient reconstruction at boundaries.
 *============================================================================*/
 
/*
  This file is part of code_saturne, a general-purpose CFD tool.
 
  Copyright (C) 1998-2025 EDF S.A.
 
  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.
*/
 
/*----------------------------------------------------------------------------*/
 
/*----------------------------------------------------------------------------
 *  Local headers
 *----------------------------------------------------------------------------*/
 
#include "base/cs_base.h"
#include "base/cs_dispatch.h"
#include "base/cs_field.h"
#include "base/cs_halo.h"
#include "mesh/cs_mesh.h"
#include "mesh/cs_mesh_quantities.h"
 
/*----------------------------------------------------------------------------*/
 
#ifdef __cplusplus
 
/*=============================================================================
 * Local Macro definitions
 *============================================================================*/
 
/*============================================================================
 * Type definition
 *============================================================================*/
 
/*============================================================================
 *  Global variables
 *============================================================================*/
 
/*============================================================================
 * Public function prototypes
 *============================================================================*/
 
/*----------------------------------------------------------------------------*/
/*
 * \brief  Compute the values of a scalar at boundary face I' positions
 *         using least-squares interpolation.
 *
 * This assumes ghost cell values for the variable (var) are up-to-date.
 *
 * A simple limiter is applied to ensure the maximum principle is preserved
 * (using non-reconstructed values in case of non-homogeneous Neumann
 * conditions).
 *
 * \remark
 *
 * To compute the values at I', we only need the gradient along II', so
 * in most cases, we could simply assume a Neumann BC for a given face.
 *
 * We still use the provided BC's when possible, for the following cases:
 * - Given a non-uniform Dirichlet condition and a non-orthogonal mesh,
 *   the Dirichlet values at face centers (shifted by II' relative to I')
 *   can convey a portion of the information of the gradient along II'.
 * - For cells with multiple boundary faces, information from faces whose
 *   normals are not orthogonal to II' can also provide a significant
 *   contribution to the normal.
 *
 * \param[in]   ctx             Reference to dispatch context
 * \param[in]   m               pointer to associated mesh structure
 * \param[in]   fvq             pointer to associated finite volume quantities
 * \param[in]   n_faces         number of faces at which to compute values
 * \param[in]   face_ids        ids of boundary faces at which to compute
 *                              values, or null for all
 * \param[in]   halo_type       halo (cell neighborhood) type
 * \param[in]   clip_coeff      clipping (limiter) coefficient
 *                              (no limiter if < 0)
 * \param[in]   hyd_p_flag      flag for hydrostatic pressure
 * \param[in]   f_ext           exterior force generating pressure
 * \param[in]   df_limiter      diffusion clipping (limiter) field
 * \param[in]   bc_coeffs       boundary condition structure, or null
 * \param[in]   c_weight        cell variable weight, or null
 * \param[in]   var             variable values et cell centers
 * \param[out]  var_iprime      variable values et face iprime locations
 * \param[out]  var_iprime_lim  limited variable values at face iprime locations
 */
/*----------------------------------------------------------------------------*/
 
void
cs_gradient_boundary_iprime_lsq_s
  (cs_dispatch_context           &ctx,
   const cs_mesh_t               *m,
   const cs_mesh_quantities_t    *fvq,
   cs_lnum_t                      n_faces,
   const cs_lnum_t               *face_ids,
   cs_halo_type_t                 halo_type,
   double                         clip_coeff,
   int                            hyd_p_flag,
   cs_real_t                      f_ext[][3],
   cs_real_t                     *df_limiter,
   const cs_field_bc_coeffs_t    *bc_coeffs,
   const cs_real_t                c_weight[],
   const cs_real_t                var[],
   cs_real_t                     *var_iprime,
   cs_real_t                      var_iprime_lim[]);
 
/*----------------------------------------------------------------------------*/
/*
 * \brief  Compute the values of a scalar at boundary face I' positions
 *         using least-squares interpolation with anisotropic weighting.
 *
 * This assumes ghost cell values for the variable (var) are up-to-date.
 *
 * A simple limiter is applied to ensure the maximum principle is preserved
 * (using non-reconstructed values in case of non-homogeneous Neumann
 * conditions).
 *
 * \remark The same remark applies as for \ref cs_gradient_boundary_iprime_lsq_s.
 *
 * \param[in]   ctx             Reference to dispatch context
 * \param[in]   m               pointer to associated mesh structure
 * \param[in]   fvq             pointer to associated finite volume quantities
 * \param[in]   n_faces         number of faces at which to compute values
 * \param[in]   face_ids        ids of boundary faces at which to compute
 *                              values, or null for all
 * \param[in]   clip_coeff      clipping (limiter) coefficient
 *                              (no limiter if < 0)
 * \param[in]   hyd_p_flag      flag for hydrostatic pressure
 * \param[in]   f_ext           exterior force generating pressure
 * \param[in]   df_limiter      diffusion clipping (limiter) field
 * \param[in]   bc_coeffs       boundary condition structure
 * \param[in]   viscel          symmetric cell tensor \f$ \tens{\mu}_\celli \f$,
                                or nullptr
 * \param[in]   weighb          boundary face weight for cells i in case
 *                              of tensor diffusion, or nullptr
 * \param[in]   c_weight        cell variable weight, or null
 * \param[in]   var             variable values et cell centers
 * \param[out]  var_iprime      variable values et face iprime locations
 * \param[out]  var_iprime_lim  limited variable values at face iprime locations
 */
/*----------------------------------------------------------------------------*/
 
void
cs_gradient_boundary_iprime_lsq_s_ani
  (cs_dispatch_context         &ctx,
   const cs_mesh_t             *m,
   const cs_mesh_quantities_t  *fvq,
   cs_lnum_t                    n_faces,
   const cs_lnum_t             *face_ids,
   double                       clip_coeff,
   int                          hyd_p_flag,
   cs_real_t                    f_ext[][3],
   cs_real_t                   *df_limiter,
   const cs_field_bc_coeffs_t  *bc_coeffs,
   cs_real_t                    viscel[][6],
   const cs_real_t              weighb[],
   const cs_real_t              c_weight[][6],
   const cs_real_t              var[],
   cs_real_t                   *var_iprime,
   cs_real_t                    var_iprime_lim[]);
 
/*----------------------------------------------------------------------------*/
/*
 * \brief  Compute the values of a vector at boundary face I' positions
 *         using least-squares interpolation.
 *
 * This assumes ghost cell values which might be used are already
 * synchronized.
 *
 * A simple limiter is applied to ensure the maximum principle is preserved
 * (using non-reconstructed values in case of non-homogeneous Neumann
 * conditions).
 *
 * This function uses a local iterative approach to compute the cell gradient,
 * as handling of the boundary condition terms b in higher dimensions
 * would otherwise require solving higher-dimensional systems, often at
 * a higher cost.
 *
 * \remark
 *
 * To compute the values at I', we only need the gradient along II', so
 * in most cases, we could simply assume a Neuman BC.
 *
 * The same logic is applied as for \ref cs_gradient_boundary_iprime_lsq_s.
 *
 * \param[in]   ctx             Reference to dispatch context
 * \param[in]   m               pointer to associated mesh structure
 * \param[in]   fvq             pointer to associated finite volume quantities
 * \param[in]   n_faces         number of faces at which to compute values
 * \param[in]   face_ids        ids of boundary faces at which to compute
 *                              values, or NULL for all
 * \param[in]   halo_type       halo (cell neighborhood) type
 * \param[in]   b_clip_coeff    boundary clipping (limiter) coefficient
 *                              (no limiter if < 0)
 * \param[in]   df_limiter      diffusion clipping (limiter) field
 *                              (no limiter if nullptr)
 * \param[in]   bc_coeffs       boundary condition structure, or NULL
 * \param[in]   c_weight        cell variable weight, or NULL
 * \param[in]   var             variable values at cell centers
 * \param[out]  var_iprime      variable values at face iprime locations
 * \param[out]  var_iprime_lim  limited variable values at face iprime locations
 */
/*----------------------------------------------------------------------------*/
 
template <cs_lnum_t stride>
void
cs_gradient_boundary_iprime_lsq_strided
  (cs_dispatch_context        &ctx,
   const cs_mesh_t            *m,
   const cs_mesh_quantities_t *fvq,
   cs_lnum_t                   n_faces,
   const cs_lnum_t            *face_ids,
   cs_halo_type_t              halo_type,
   double                      b_clip_coeff,
   cs_real_t                  *df_limiter,
   const cs_field_bc_coeffs_t *bc_coeffs,
   const cs_real_t             c_weight[],
   const cs_real_t             var[][stride],
   cs_real_t                   var_iprime[][stride],
   cs_real_t                   var_iprime_lim[][stride]);
 
/*----------------------------------------------------------------------------*/
 
#endif /* cplusplus */
 
#endif /* CS_GRADIENT_BOUNDARY */