MomentumPhysics2D.hpp

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// SPDX-License-Identifier: Apache-2.0
// Copyright 2026 Caleb Buahin
#ifndef OPENSWMM_MOMENTUM_PHYSICS_2D_HPP
#define OPENSWMM_MOMENTUM_PHYSICS_2D_HPP
 
#include <array>
#include <algorithm>
#include <cmath>
#include <limits>
#include <cstdint>
#include <vector>
 
namespace openswmm::twoD {
struct MeshData;
struct InertialEdges;
struct BoundaryData;

class MomentumPhysics2D {
public:
    std::vector<double> viscosity, strain, vorticity; 
    std::vector<double> wall_distance;
    static constexpr double kappa = 0.41;
    double last_limit = std::numeric_limits<double>::infinity();
    uint64_t substeps = 0, retries = 0;

    static double wallDrag(const MeshData& m, const BoundaryData& b,
                           const std::vector<int>& slots, const std::vector<double>& h,
                           const std::vector<double>& eta, std::vector<double>& qx,
                           std::vector<double>& qy, double dry, double seconds, bool vfr);
 
    static void rotate(std::vector<double>& qx, std::vector<double>& qy, double angle);

    double evaluate(const MeshData& m, const InertialEdges& edges, const std::vector<double>& h,
                    const std::vector<double>& eta, const std::vector<double>& qx,
                    const std::vector<double>& qy, double dry, double cs, std::vector<double>& rx,
                    std::vector<double>& ry, double fixed_viscosity = -1, double background = 0,
                    double depth_coefficient = 0);

    void advance(const MeshData& m, const InertialEdges& edges, const std::vector<double>& h,
                 const std::vector<double>& eta, std::vector<double>& qx, std::vector<double>& qy,
                 double dry, double cs, double seconds, double background = 0,
                 double depth_coefficient = 0);

    void computeWallDistance(const MeshData& m);
 
    static double energy(const MeshData& m, const std::vector<double>& h,
                         const std::vector<double>& qx, const std::vector<double>& qy, double dry);
 
private:
    struct Stencil {
        std::array<int, 5> ids{};
        std::array<double, 5> gx{}, gy{};
        int count = 0;
    };
    std::vector<Stencil> stencils_;
    std::vector<uint8_t> connected_;
    std::vector<double> bound_x_, bound_y_, rx_, ry_, sx_, sy_, tx_, ty_;
};
} // namespace openswmm::twoD
#endif