ERF_SurfaceLayerStress.H

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#ifndef ERF_SURFACE_LAYER_STRESS_H_
#define ERF_SURFACE_LAYER_STRESS_H_
 
#include "AMReX_GpuQualifiers.H"
#include "AMReX_REAL.H"
 
namespace surface_layer_stress {
 
/** LSM cache value from a conservative face stress. */
AMREX_GPU_HOST_DEVICE
AMREX_FORCE_INLINE
amrex::Real
conservative_to_kinematic_stress(
  amrex::Real conservative_stress, amrex::Real rho)
{
  return conservative_stress / rho;
}
 
/** Test one LSM side without coupling validity to another component's handle.
 */
AMREX_GPU_HOST_DEVICE
AMREX_FORCE_INLINE
bool
lsm_flux_is_valid(
  bool has_flux, bool is_land, amrex::Real flux, amrex::Real undefined)
{
  return has_flux && is_land && flux < undefined;
}
 
struct FaceStressResult
{
  amrex::Real face_stress;
  amrex::Real low_kinematic_cache;
  amrex::Real high_kinematic_cache;
};
 
/**
 * Combine cell-centered kinematic LSM stresses with a conservative MOST
 * fallback stress at one face. The returned cache values are always
 * kinematic, while face_stress is always conservative.
 */
AMREX_GPU_HOST_DEVICE
AMREX_FORCE_INLINE
FaceStressResult
combine_lsm_and_most_stress(
  amrex::Real rho_low,
  amrex::Real rho_high,
  amrex::Real kinematic_low,
  amrex::Real kinematic_high,
  bool low_valid,
  bool high_valid,
  amrex::Real most_face_stress)
{
  const amrex::Real half = amrex::Real(0.5);
  FaceStressResult result{
    amrex::Real(0.0),
    low_valid ? kinematic_low
              : conservative_to_kinematic_stress(most_face_stress, rho_low),
    high_valid ? kinematic_high
               : conservative_to_kinematic_stress(most_face_stress, rho_high)};
 
  if (low_valid && high_valid) {
    result.face_stress =
      half * rho_low * kinematic_low + half * rho_high * kinematic_high;
  } else if (low_valid) {
    result.face_stress =
      half * rho_low * kinematic_low + half * most_face_stress;
  } else if (high_valid) {
    result.face_stress =
      half * rho_high * kinematic_high + half * most_face_stress;
  } else {
    result.face_stress = most_face_stress;
  }
 
  return result;
}
 
} // namespace surface_layer_stress
 
#endif