riemann_dust_huang_bai.hpp

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// -------------------------------------------------------//
//
// SHAMROCK code for hydrodynamics
// Copyright (c) 2021-2026 Timothée David--Cléris <tim.shamrock@proton.me>
// SPDX-License-Identifier: CeCILL Free Software License Agreement v2.1
// Shamrock is licensed under the CeCILL 2.1 License, see LICENSE for more information
//
// -------------------------------------------------------//
 
#pragma once

 
#include "shammath/riemann_common.hpp"
 
namespace shammath {

    template<DustFluidStateSpec FSpec>
    inline constexpr typename FSpec::Tcons huang_bai_flux(
        const FSpec &fspec,
        const typename FSpec::Tprim &prim_l,
        const typename FSpec::Tprim &prim_r,
        const typename FSpec::Tvec &n) {
        using Tscal = typename FSpec::Tscal;
        using Tcons = typename FSpec::Tcons;
 
        const Tscal vn_l = fspec.vn(prim_l, n);
        const Tscal vn_r = fspec.vn(prim_r, n);
 
        const Tcons f_l = fspec.flux(prim_l, n, vn_l);
        const Tcons f_r = fspec.flux(prim_r, n, vn_r);
 
        Tcons flux{};
 
        if (vn_l > 0 && vn_r > 0)
            flux = f_l;
        else if (vn_l < 0 && vn_r < 0)
            flux = f_r;
        else if (vn_l < 0 && vn_r > 0)
            flux *= 0;
        else if (vn_l > 0 && vn_r < 0)
            flux = (f_l + f_r);
 
        return flux;
    }
 
} // namespace shammath