HT_CPP.md

Basic example of using C++ for a HT simulation.

input.h

#ifndef INPUT_H
#define INPUT_H

#include <iostream>
#include <fstream>
#include <cmath>


// User Constants
const double radius = 1.2e-2;
const double density = 8800.0;
const double specific_heat = 400.0;

const double initial_temperature = 800.0;
const double atmospheric_temperature = 15.0;

// Universal Constants
const double sigma = 5.67e-8;

// Programamatic Constants
const double t_simulation = 30.0 * 60.0;
const double t_step = 1e-2;

const int n_steps = static_cast<int>(std::round(t_simulation / t_step));
const int t_logging = n_steps / 10000;

// Macros
#define SQ(x) ((x) * (x))
#define CU(x) ((x) * (x) * (x))
#define QU(x) ((x) * (x) * (x) * (x))

#endif

main.cpp

#include "./input.h"
#include "./problem.h"

int main() {

	std::cout << "HT Simulation Test..." << std::endl;

	Problem prob(initial_temperature);

	for (prob.time_step = 1; prob.time_step < n_steps; prob.time_step++) {

		prob.calc_temperature();

		if (prob.time_step % t_logging == 0) {
			prob.write_file();
		}

	}

	std::cout << "Simulation Finished..." << std::endl;

	return 0;

}

problem.cpp

#include "./input.h"
#include "./problem.h"

void Problem::calc_temperature() {
	
	update_gradient();
	temperature = temperature - temperature_grad * t_step;

}

void Problem::write_file() {
	
	std::ofstream output;
	output.precision(10);
	output.open("results.csv", std::ios::out | std::ios::app);

	output << time_step * t_step << ", " << temperature << ", " << temperature_grad << "\n";
	output.close();

}

void Problem::update_gradient() {
	
	temperature_grad = 3.0 * (sigma / (radius * density * specific_heat)) * (QU(temperature) - QU(atmospheric_temperature));

}


// Custom Constructor
Problem::Problem(double initial_temp) {

	std::cout << "Initialising Problem..." << std::endl;;

	time_step = 0;
	temperature = initial_temp;

}


// Defaul Constructor
Problem::Problem() {

	std::cout << "Initialising Problem..." << std::endl;

	time_step = 0;
	temperature = 100.0;

}

problem.h

#ifndef PROBLEM_H
#define PROBLEM_H

class Problem {

public: // con/de-structors

	Problem();
	~Problem() {};

	Problem(double initial_temp);

public: // attributes

	int time_step;
	double temperature;
	double temperature_grad;

private: // attributes

public: // methods

	void calc_temperature();
	void write_file();

private: // methods

	void update_gradient();


};

#endif