phonon.h

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#ifndef PSIM_PHONON_H
#define PSIM_PHONON_H
 
#include <array>// for array
#include <cstddef>// for size_t
#include <ostream>// for operator<<, basic_ostream, basic_ostream<>::__ost...
#include <utility>// for pair
 
class Cell;
 
namespace Geometry {
struct Line;
struct Point;
}// namespace Geometry
 
class Phonon {
public:
    static constexpr std::size_t NUM_RELAX_RATES = 3;
    enum class Polarization { LA, TA };
 
    using RelaxRates = std::array<double, NUM_RELAX_RATES>;
 
    Phonon(signed char sign, double lifetime, Cell* cell);
 
    [[nodiscard]] signed char getSign() const noexcept {
        return sign_;
    }
    [[nodiscard]] std::pair<double, double> getPosition() const noexcept {
        return { px_, py_ };
    }
    [[nodiscard]] std::pair<double, double> getVelVector() const noexcept {
        return { dx_ * velocity_, dy_ * velocity_ };
    }
    [[nodiscard]] std::pair<double, double> getDirection() const noexcept {
        return { dx_, dy_ };
    }
    [[nodiscard]] std::size_t getFreqIndex() const noexcept {
        return freq_index_;
    }
    [[nodiscard]] double getFreq() const noexcept {
        return freq_;
    }
    [[nodiscard]] Polarization getPolar() const noexcept {
        return polar_;
    }
    [[nodiscard]] double getLifetime() const noexcept {
        return lifetime_;
    }
    [[nodiscard]] std::size_t getLifeStep() const noexcept {
        return lifestep_;
    }
    [[nodiscard]] bool outsideCell() const noexcept {
        return cell_ == nullptr;
    }
 
    void scatterUpdate(std::size_t freq_index, double freq, double velocity, Polarization polar) noexcept;
    void setPosition(double px, double py) noexcept {// NOLINT
        px_ = px;
        py_ = py;
    }
    void setDirection(double dx, double dy) noexcept {// NOLINT
        dx_ = dx;
        dy_ = dy;
    }
    void setCell(Cell* cell) noexcept {
        cell_ = cell;
    }
    void setLifeStep(std::size_t step) {
        lifestep_ = step;
    }
    void scatterUpdate();
    void drift(double time) noexcept;
    void setRandDirection() noexcept;
 
    // All these methods will throw if the phonon is not in a cell (cell_ == nullptr)
    [[nodiscard]] std::size_t getCellSensorID() const;
    [[nodiscard]] std::size_t getCellMaterialID() const;
    [[nodiscard]] double getCellHeatCapacityAtFreq(std::size_t index) const;
    [[nodiscard]] RelaxRates getRelaxRates(std::size_t step) const;
    [[nodiscard]] std::array<Geometry::Line, 3> getCellBoundaryLines() const;
    void handleSurfaceCollision(const Geometry::Point& poi, double step_time);
    void updateCellHeatParams(std::size_t step) const;
    void setRandPoint(double r1, double r2);// NOLINT
 
    friend std::ostream& operator<<(std::ostream& os, const Phonon& phonon) {// NOLINT
        os << "px: " << phonon.px_ << " py: " << phonon.py_ << "\nvx_: " << phonon.dx_ * phonon.velocity_
           << " vy_: " << phonon.dy_ * phonon.velocity_;
        return os;
    }
 
private:
    signed char sign_;// Determines how the phonon energy/flux is handled (-1, 1)
    double lifetime_;
    std::size_t lifestep_{ 0 };
 
    double px_{ 0. };
    double py_{ 0. };
    double dx_{ 0. };
    double dy_{ 0. };
 
    std::size_t freq_index_{ 0 };
    double freq_{ 0. };
    double velocity_{ 0. };
    Polarization polar_{ Polarization::LA };
 
    Cell* cell_{ nullptr };
};
 
#endif// PSIM_PHONON_H