UNO.hh

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/* Copyright (C) 2020, 2021, 2022 PISM Authors
 *
 * This file is part of PISM.
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 * PISM is free software; you can redistribute it and/or modify it under the
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#ifndef PISM_UNO_2D_H
#define PISM_UNO_2D_H
 
#include "pism/util/array/Scalar.hh"
#include "pism/util/array/Vector.hh"
#include "pism/util/array/Staggered.hh"
 
namespace pism {
 
class Grid;
 
namespace array {
class CellType1;
} // end of namespace array
 
enum UNOType {PISM_UNO_UPWIND1, PISM_UNO_LAX_WENDROFF, PISM_UNO_FROMM, PISM_UNO_2, PISM_UNO_3};
 
/*!
 * Implementation of Upwind Nonoscillatory advection schemes UNO2 and UNO3.
 *
 * See J.-G. Li, “Upstream Nonoscillatory Advection Schemes,” Monthly Weather Review, vol.
 * 136, Art. no. 12, Dec. 2008.
 *
 * Three more schemes (first-order upwinding, Lax-Wendroff and Fromm) can be stated in the
 * same framework and so we implement them as well since this requires very little effort
 * and simplifies testing and comparisons.
 */
class UNO {
public:
  UNO(std::shared_ptr<const Grid> grid, UNOType type);
 
  void update(double dt,
              const array::CellType1 &cell_type,
              const array::Scalar &x,
              const array::Vector &velocity,
              bool nonnegative = false);
 
  const array::Scalar& x() const;
 
private:
  void compute_interface_fluxes(const array::CellType1 &cell_type,
                                const array::Vector1 &velocity,
                                const array::Scalar2 &x_old,
                                double dt,
                                array::Staggered &result) const;
 
  typedef double (*MidFluxApproximation)(const double *, const double *, size_t, double, double, double);
 
  MidFluxApproximation m_approx;
 
  // interface fluxes (on the staggered grid; ghosted)
  array::Staggered1 m_q, m_q_limited;
 
  // ghosted copy of the input velocity field used to compute interface velocities
  array::Vector1 m_v_ghosted;
 
  // temporary storage for the old state of the advected quantity (ghosted, width=2)
  //
  // used to perform the step using flux divergence *and* to compute interface fluxes
  // (this requires a wide stencil)
  array::Scalar2 m_x_ghosted;
 
  // resulting advected quantity (not ghosted)
  array::Scalar m_x;
};
class UNO {…};
 
} // end of namespace pism
 
#endif /* PISM_UNO_2D_H */