Dust.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 "shambase/assert.hpp"
#include "shambase/constants.hpp"
#include "shambackends/sycl.hpp"
 
namespace shamphys {
 
    template<class T>
    inline T epstein_supersonic_correction(T delta_v, T cs) noexcept {
 
        SHAM_ASSERT(cs > 0);
 
        auto div = delta_v / cs;
        return sycl::sqrt(T(1.0) + T(9.0 / 128.0) * shambase::constants::pi<T> * div * div);
    }
 
    template<class T>
    inline T epstein_stopping_time(
        T rho_grain, T s_grain, T rho, T cs, T gamma, T f = T(1.0)) noexcept {
 
        SHAM_ASSERT(rho * cs * f > 0);
        SHAM_ASSERT(gamma > 0);
 
        return (rho_grain * s_grain / (rho * cs * f))
               * sycl::sqrt(shambase::constants::pi<T> * gamma / T(8));
    }
 
} // namespace shamphys