density_ops.H

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#ifndef DENSITY_OPS_H
#define DENSITY_OPS_H
 
#include "amr-wind/equation_systems/density/density.H"
#include "AMReX_REAL.H"
 
using namespace amrex::literals;
 
namespace amr_wind::pde {
 
template <typename Scheme>
struct ComputeRHSOp<Density, Scheme>
{
    explicit ComputeRHSOp(PDEFields& fields_in) : fields(fields_in) {}
 
    void predictor_rhs(
        const DiffusionType /*unused*/,
        const amrex::Real dt,
        bool /*mesh_mapping*/)
    {
        // Field states for diffusion and advection terms. In Godunov scheme
        // these terms only have one state.
        auto fstate = std::is_same<Scheme, fvm::Godunov>::value
                          ? FieldState::New
                          : FieldState::Old;
 
        const int nlevels = fields.repo.num_active_levels();
        auto& field = fields.field;
        const auto& field_old = field.state(FieldState::Old);
        const auto& conv_term = fields.conv_term.state(fstate);
 
        for (int lev = 0; lev < nlevels; ++lev) {
            const auto& rho_arrs = field(lev).arrays();
            const auto& rho_o_arrs = field_old(lev).const_arrays();
            const auto& ddt_o_arrs = conv_term(lev).const_arrays();
 
            amrex::ParallelFor(
                field(lev),
                [=] AMREX_GPU_DEVICE(int nbx, int i, int j, int k) noexcept {
                    rho_arrs[nbx](i, j, k) = rho_o_arrs[nbx](i, j, k) +
                                             dt * ddt_o_arrs[nbx](i, j, k);
                    // Defer n+1/2 update to the time-stepping algorithm
                    // rho_nph(i, j, k) = 0.5_rt * (rho(i, j, k) + rho_o(i, j,
                    // k));
                });
        }
        amrex::Gpu::streamSynchronize();
    }
 
    void corrector_rhs(
        const DiffusionType /*unused*/,
        const amrex::Real dt,
        bool /*mesh_mapping*/)
    {
        const int nlevels = fields.repo.num_active_levels();
        auto& field = fields.field;
        const auto& field_old = field.state(FieldState::Old);
        const auto& conv_term = fields.conv_term;
        const auto& conv_term_old = fields.conv_term.state(FieldState::Old);
 
        for (int lev = 0; lev < nlevels; ++lev) {
            const auto& rho_arrs = field(lev).arrays();
            const auto& rho_o_arrs = field_old(lev).const_arrays();
            const auto& ddt_arrs = conv_term(lev).const_arrays();
            const auto& ddt_o_arrs = conv_term_old(lev).const_arrays();
 
            amrex::ParallelFor(
                field(lev),
                [=] AMREX_GPU_DEVICE(int nbx, int i, int j, int k) noexcept {
                    rho_arrs[nbx](i, j, k) =
                        rho_o_arrs[nbx](i, j, k) +
                        dt * 0.5_rt *
                            (ddt_o_arrs[nbx](i, j, k) + ddt_arrs[nbx](i, j, k));
                    // Defer n+1/2 update to time-stepping algorithm
                    // rho_nph(i, j, k) =
                    //     0.5_rt * (rho(i, j, k) + rho_o(i, j, k));
                });
        }
        amrex::Gpu::streamSynchronize();
    }
 
    void improve_explicit_diff(const amrex::Real /*unused*/) {}
 
    // data members
    PDEFields& fields;
};
} // namespace amr_wind::pde
 
#endif /* DENSITY_OPS_H */