281 lines
7.3 KiB
C++
281 lines
7.3 KiB
C++
/** @file PenningTrap.cpp
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*
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* @author Cory Alexander Balaton (coryab)
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* @author Janita Ovidie Sandtrøen Willumsen (janitaws)
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*
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* @version 0.1
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*
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* @brief The implementation of the PenningTrap class.
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*
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* @bug No known bugs
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* */
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#include "PenningTrap.hpp"
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#include "constants.hpp"
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#include "typedefs.hpp"
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#include "utils.hpp"
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PenningTrap::PenningTrap(double B_0, std::function<double(double)> V_0,
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double d, double t)
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{
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this->B_0 = B_0;
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this->V_0 = V_0;
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this->d = d;
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this->t = t;
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}
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PenningTrap::PenningTrap(unsigned int i, double B_0,
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std::function<double(double)> V_0, double d, double t)
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: PenningTrap::PenningTrap(B_0, V_0, d)
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{
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vec_3d r, v;
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for (size_t j = 0; j < i; j++) {
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r = vec_3d().randn() * .1 * this->d;
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v = vec_3d().randn() * .1 * this->d;
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this->add_particle(Particle(1., 40., r, v));
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}
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}
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PenningTrap::PenningTrap(std::vector<Particle> particles, double B_0,
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std::function<double(double)> V_0, double d, double t)
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: PenningTrap::PenningTrap(B_0, V_0, d)
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{
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this->particles = particles;
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}
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vec_3d PenningTrap::v_func(unsigned int i, unsigned int j, double dt)
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{
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switch (i) {
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case 0:
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return .5 * dt * this->k_v[0][j];
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case 1:
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return .5 * dt * this->k_v[1][j];
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case 2:
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return dt * this->k_v[2][j];
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case 3:
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return (dt / 6.) * (this->k_v[0][j].eval() + this->k_v[1][j].eval() +
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this->k_v[2][j].eval() + this->k_v[3][j].eval());
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default:
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std::cout << "Not valid!" << std::endl;
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abort();
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}
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}
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vec_3d PenningTrap::r_func(unsigned int i, unsigned int j, double dt)
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{
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switch (i) {
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case 0:
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return .5 * dt * this->k_r[0][j];
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case 1:
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return .5 * dt * this->k_r[1][j];
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case 2:
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return dt * this->k_r[2][j];
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case 3:
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return (dt / 6.) * (this->k_r[0][j].eval() + this->k_r[1][j].eval() +
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this->k_r[2][j].eval() + this->k_r[3][j].eval());
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default:
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std::cout << "Not valid!" << std::endl;
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abort();
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}
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}
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void PenningTrap::add_particle(Particle particle)
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{
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this->particles.push_back(particle);
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}
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vec_3d PenningTrap::external_E_field(vec_3d r)
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{
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r(2) *= -2.;
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double f = this->V_0(this->t) / (this->d * this->d);
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return f * r;
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}
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vec_3d PenningTrap::external_B_field(vec_3d r)
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{
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return vec_3d{0., 0., this->B_0};
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}
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vec_3d PenningTrap::force_on_particle(unsigned int i, unsigned int j)
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{
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Particle p_j = this->particles[j];
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// Calculate the difference between the particles' position
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vec_3d res = this->particles[i].r_vec - p_j.r_vec;
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// Get the distance between the particles
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double norm = arma::norm(res, 2);
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// Multiply res with p_j's charge divided by the norm cubed
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return vec_3d(res * p_j.q / (norm * norm * norm));
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}
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vec_3d PenningTrap::total_force_external(unsigned int i)
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{
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Particle p = this->particles[i];
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if (arma::norm(p.r_vec) > this->d) {
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return vec_3d{0., 0., 0.};
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}
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vec_3d force =
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p.q * (this->external_E_field(p.r_vec) +
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arma::cross(p.v_vec, this->external_B_field(p.r_vec)));
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return force;
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}
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vec_3d PenningTrap::total_force_particles(unsigned int i)
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{
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Particle p = this->particles[i];
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vec_3d res;
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for (size_t j = 0; j < this->particles.size(); j++) {
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if (i == j) {
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continue;
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}
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res += this->force_on_particle(i, j);
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}
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return vec_3d(res * K_E * (p.q / p.m));
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}
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vec_3d PenningTrap::total_force(unsigned int i)
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{
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return this->total_force_external(i) - this->total_force_particles(i);
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}
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void PenningTrap::evolve_RK4(double dt, bool particle_interaction)
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{
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std::vector<Particle> original_particles = this->particles;
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std::vector<Particle> tmp_particles = this->particles;
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vec_3d (PenningTrap::*force)(unsigned int);
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if (particle_interaction) {
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force = &PenningTrap::total_force;
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}
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else {
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force = &PenningTrap::total_force_external;
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}
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size_t size = this->particles.size();
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this->k_v = sim_arr(4, sim_cols(size));
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this->k_r = sim_arr(4, sim_cols(size));
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for (size_t i = 0; i < 4; i++) {
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#pragma omp parallel for
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for (size_t j = 0; j < this->particles.size(); j++) {
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this->k_v[i][j] = (this->*force)(j) / this->particles[j].m;
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this->k_r[i][j] = this->particles[j].v_vec;
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Particle *p = &tmp_particles[j];
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p->v_vec = original_particles[j].v_vec + this->v_func(i, j, dt);
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p->r_vec = original_particles[j].r_vec + this->r_func(i, j, dt);
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}
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this->particles = tmp_particles;
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}
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this->t += dt;
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}
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void PenningTrap::evolve_forward_euler(double dt, bool particle_interaction)
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{
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std::vector<Particle> new_state = this->particles;
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Particle *p;
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vec_3d (PenningTrap::*force)(unsigned int);
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if (particle_interaction) {
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force = &PenningTrap::total_force;
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}
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else {
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force = &PenningTrap::total_force_external;
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}
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#pragma omp parallel for private(p)
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for (size_t i = 0; i < this->particles.size(); i++) {
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p = &new_state[i];
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p->v_vec += dt * (this->*force)(i) / p->m;
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p->r_vec += dt * this->particles[i].v_vec;
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}
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this->particles = new_state;
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this->t += dt;
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}
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sim_arr PenningTrap::simulate(double time, unsigned int steps,
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std::string method, bool particle_interaction)
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{
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double dt = time / (double)steps;
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sim_arr res(this->particles.size(), sim_cols(steps));
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void (PenningTrap::*func)(double, bool);
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if (method == "rk4") {
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func = &PenningTrap::evolve_RK4;
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}
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else if (method == "euler") {
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func = &PenningTrap::evolve_forward_euler;
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}
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else {
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std::cout << "Not a valid method!" << std::endl;
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abort();
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}
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for (size_t j = 0; j < steps; j++) {
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for (size_t i = 0; i < this->particles.size(); i++) {
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res[i][j] = this->particles[i].r_vec;
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}
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(this->*func)(dt, particle_interaction);
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}
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return res;
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}
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void PenningTrap::write_simulation_to_dir(std::string path, double time,
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unsigned int steps, std::string method,
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bool particle_interaction)
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{
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if (path.back() != '/') {
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path += '/';
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}
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if (mkpath(path, 0777) != 0) {
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std::cout << "Hello" << std::endl;
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return;
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}
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sim_arr res = this->simulate(time, steps, method, particle_interaction);
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std::ofstream ofile;
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#pragma omp parallel for private(ofile)
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for (size_t i = 0; i < this->particles.size(); i++) {
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ofile.open(path + "particle_" + std::to_string(i) + ".txt");
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for (vec_3d &vec : res[i]) {
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ofile << vec(0) << "," << vec(1) << "," << vec(2) << "\n";
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}
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ofile.close();
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}
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}
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double PenningTrap::fraction_of_particles_left(double time, unsigned int steps, std::string method, bool particle_interaction)
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{
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sim_arr res = this->simulate(time, steps, method, particle_interaction);
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int particles_left = 0;
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for (Particle p : this->particles) {
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if (arma::norm(p.r_vec) < this->d) {
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particles_left++;
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}
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}
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return (double) particles_left / (double) this->particles.size();
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}
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