diff --git a/Project/Main.m b/Project/Main.m new file mode 100644 index 0000000..fa32fe4 --- /dev/null +++ b/Project/Main.m @@ -0,0 +1,281 @@ +% Axisymmetric mug +% r–z plane, rotation around r = 0 +clear; clc; close all; + +%% General values that we use in the entire script +%Task 3) Thermal conductivity +lambda_wall = 30; % ceramic +lambda_fluid = 0.6089; % water +lambda_air = 0.026; % air +%Task 4) +alpha = 10; % heat transfer coefficient +u_out = 18; % ambient air temperature (°C) +%Task 6) Volumetric heat capacities: rho * c_p +% Densities [kg/m^3] +rho_wall = 2400; % ceramic +rho_fluid = 1000; % water +rho_air = 1.2; % air +% Specific heats [J/(kg*K)] +cp_wall = 900; +cp_fluid = 4184; +cp_air = 1005; +% Volumetric heat capacities [J/(m^3*K)] +c_wall = rho_wall * cp_wall; +c_fluid = rho_fluid * cp_fluid; +c_air = rho_air * cp_air; + +%% Task 1: Mesh definition +% Create PDE model +model = createpde(); + +% Points (meters) +A = [0, 0]; B = [0.055, 0]; +C = [0.083, 0.105]; H = [0.078, 0.105]; +F = [0.050, 0.005]; E = [0, 0.005]; +G = [0.067, 0.066]; I = [0, 0.066]; +D = [0, 0.105]; + +% Geometry matrix (edges) +g1 = [2; A(1); E(1); A(2); E(2); 1; 0]; % Axis - ceramic +g2 = [2; E(1); I(1); E(2); I(2); 2; 0]; % Axis - fluid +g3 = [2; I(1); D(1); I(2); D(2); 3; 0]; % Axis - air +g4 = [2; A(1); B(1); A(2); B(2); 1; 0]; % Outer ceramic +g5 = [2; B(1); C(1); B(2); C(2); 1; 0]; % Outer ceramic +g6 = [2; C(1); H(1); C(2); H(2); 1; 3]; % Top rim: (C-H) ceramic-air +g7 = [2; H(1); F(1); H(2); F(2); 1; 3]; % Inner ceramic wall (H-F) ceramic-air +g8 = [2; F(1); E(1); F(2); E(2); 1; 2]; % Inner ceramic bottom (F-E) ceramic-fluid +g9 = [2; F(1); G(1); F(2); G(2); 2; 3]; % Fluid surface (F-G) fluid-air +g10 = [2; G(1); I(1); G(2); I(2); 2; 3]; % Fluid surface (G-I) fluid-air +g11 = [2; D(1); H(1); D(2); H(2); 3; 0]; % Air top boundary: (D-H) air-outside + +% Assemble geometry +g = [g1 g2 g3 g4 g5 g6 g7 g8 g9 g10 g11]; +geometryFromEdges(model, g); + +% figure(1); +% pdegplot(model, 'EdgeLabels','on', 'FaceLabels','on'); +% axis equal; +% title('Geometry with edge and face labels'); + +% Generate mesh, linear and 3 nodes per element +mesh = generateMesh(model, 'Hmax', 0.002, 'GeometricOrder','linear'); + +% figure(2); +% pdemesh(model); +% axis equal; +% title('Generated mesh'); + +%% Task 2: Direct solver with constant lambda +nodes = mesh.Nodes; % coordinates of all mesh nodes +elements = mesh.Elements; % which nodes make up each triangle element + +Nnodes = size(nodes,2); +Nelems = size(elements,2); + +% Define material properties (for simplicity, lambda = 1 everywhere) +lambda = ones(Nelems,1); % thermal conductivity + +% Initialize global stiffness matrix and RHS +K = sparse(Nnodes, Nnodes); +F = zeros(Nnodes,1); + +% Assemble K and F +for e = 1:Nelems %Loop over each triangle element + vert = elements(:,e); %nodes of element + x = nodes(1,vert); + y = nodes(2,vert); + + Ae = polyarea(x,y); % Compute area of the triangle + + % Linear triangle gradients + b = [y(2)-y(3); y(3)-y(1); y(1)-y(2)]; % derivative with respect to x + c = [x(3)-x(2); x(1)-x(3); x(2)-x(1)]; % derivative with respect to y + + % Element stiffness matrix + Ke = (lambda(e)/(4*Ae)) * (b*b.' + c*c.'); + + % Assemble + K(vert,vert) = K(vert,vert) + Ke; + + % Element load vector (f=0) + F(vert) = F(vert) + zeros(3,1); +end + +% Find boundary nodes (couldn't find a better way) +edgesAll = [elements([1 2],:), elements([2 3],:), elements([3 1],:)]; % all edges -> 2x(3*Nelems) awway since each triangle has 3 edges +edgesSorted = sort(edgesAll,1); % sort nodes of each edge, ensure that [i,j] and [j,i] are the same +[~,~,ic] = unique(edgesSorted','rows'); % identifies unique edges and assignes indices ic +counts = accumarray(ic,1); % counts how many times each edge appears in the mesh +boundaryEdges = find(counts==1); %edges belonging to only 1 element: hence on the boundary +boundaryNodes = unique(edgesSorted(:,boundaryEdges)); % nodes belonging to these boundary edges + +% Direct solver +% Enforce Dirichlet BC strongly +K(boundaryNodes,:) = 0; +K(:,boundaryNodes) = 0; +K(boundaryNodes,boundaryNodes) = speye(length(boundaryNodes)); +F(boundaryNodes) = 0; + +% Direct solve +u = K \ F; + +% figure(3) +% pdeplot(model, 'XYData', u, 'Mesh','on'); +% axis equal; +% title('Stationary Dirichlet solution'); +% colorbar; + +%% Task 3: Laplace with multiple lambdas +[K, F] = CalculateLaplace_mult(model, lambda_wall, lambda_fluid, lambda_air); + +% Enforce Dirichlet BC strongly +K(boundaryNodes,:) = 0; +K(:,boundaryNodes) = 0; +K(boundaryNodes,boundaryNodes) = speye(length(boundaryNodes)); +F(boundaryNodes) = 0; + +% Direct solve +u = K \ F; + +% % Plot solution +% figure(4) +% pdeplot(model,'XYData',u, 'Mesh','on'); +% axis equal +% title('Task 3: Stationary solution with multiple conductivities'); +% colorbar + +%% Task 4: Robin boundary condition +[K, F] = CalculateLaplace_mult(model, lambda_wall, lambda_fluid, lambda_air); +[K, F] = ApplyRobinBC_mult(model, K, F, alpha, u_out); + +% Direct solve +u = K \ F; + +% figure(5) +% pdeplot(model, 'XYData', u, 'Mesh','on'); +% axis equal +% title('Task 4: Stationary solution with Robin BC'); +% colorbar + +%% Task 5: Axisymmetric Laplace + Robin BC +[K, F] = CalculateLaplace_mult_rot(model, lambda_wall, lambda_fluid, lambda_air); +[K, F] = ApplyRobinBC_mult_rot(model, K, F, alpha, u_out); + +% Direct solve +u = K \ F; + +% figure(6) +% pdeplot(model, 'XYData', u, 'Mesh','on'); +% axis equal +% title('Task 5: Axisymmetric stationary solution with Robin BC'); +% colorbar + +%To see it in 3D paste here the code in "AdditionalPlotCodes.txt". + +%% Task 6: Axisymmetric mass matrix +M = sparse(Nnodes, Nnodes); +M = AddMass_mult_rot(model, M, c_wall, c_fluid, c_air); + +%% Task 7: Initial solution +u0 = Init_Solution_mult(model, 18, 80, 18); + +% figure(7) +% pdeplot(model, 'XYData', u0, 'Mesh','on'); +% axis equal +% title('Initial temperature distribution'); +% colorbar + +%% Task 8: Time-dependent simulation (explicit scheme) +tau = 0.5; % time step in seconds +T_end = 400; % total simulation time (seconds) +Nt = ceil(T_end/tau); % number of time steps + +A = (1/tau)*M+K; % Left-hand side matrix +u = u0; + +for k = 1:Nt + b = (1/tau)*M*u + F; % F is the load vector, F=0 + u_next = A\b; + u = u_next; % Update + + if mod(k,20) == 0 + % figure(8) + % pdeplot(model, 'XYData', u, 'Mesh','on'); + % axis equal + % title(['Temperature at t = ', num2str(k*tau), ' s']); + % colorbar + % drawnow + end +end + +%To see the 9 snapshots paste here the codes in "AdditionalPlotCodes.txt" + +%% Task 9 (i): Heating time using inner ceramic wall temperature +T_target = 67; % [°C] +[K, F] = CalculateLaplace_mult_rot(model, lambda_wall, lambda_fluid, lambda_air); +[K, F] = ApplyRobinBC_mult_rot(model, K, F, alpha, u_out); +A = (1/tau)*M+K; % Left-hand side matrix + +innerWallNodes = findNodes(model.Mesh,'region','Edge',8); % Edge 8 = ceramic–fluid interface +u = u0; + +% Storage +timeVec = (0:Nt-1)' * tau; +innerWallTemp = zeros(Nt,1); +Twarm = NaN; + +for k = 1:Nt + b = (1/tau)*M*u + F; + + u = A\b; + + % Average inner wall temperature + innerWallTemp(k) = mean(u(innerWallNodes)); + + % Check heating criterion + if innerWallTemp(k) >= T_target + Twarm = k * tau; + fprintf('Task 9 (i): Inner wall reaches %.1f°C at T = %.1f s\n', ... + T_target, Twarm); + break + end +end + +% figure(9) +% plot(timeVec(1:k), innerWallTemp(1:k), 'LineWidth', 2) +% hold on +% yline(T_target,'r--','67°C','LineWidth',1.5) +% xlabel('Time [s]') +% ylabel('Average inner wall temperature [°C]') +% title('Heating of the inner ceramic wall') +% grid on + +%% CHECK: Insulated mug – transient redistribution +[K_neu, F_neu] = CalculateLaplace_mult_rot(model,lambda_wall,lambda_fluid,lambda_air); + +M_neu = sparse(Nnodes, Nnodes); +M_neu = AddMass_mult_rot(model,M_neu,c_wall,c_fluid,c_air); + +% Time stepping parameters +tau = 0.5; +T_end = 400; +Nt = ceil(T_end / tau); + +A_neu = (1/tau) * M_neu + K_neu; + +% Initial condition +u = u0; + +for k = 1:Nt + b = (1/tau) * M_neu * u + F_neu; + u = A_neu \ b; + + if mod(k,20) == 0 + % figure(10) + % pdeplot(model, 'XYData', u, 'Mesh','on'); + % axis equal + % title(['Insulated mug, t = ', num2str(k*tau), ' s']); + % colorbar + % drawnow + end +end \ No newline at end of file