108 lines
2.1 KiB
Matlab
Executable File
108 lines
2.1 KiB
Matlab
Executable File
%% Euler forward Dirichlet
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L = 1; % domain size (in the lecture notes this is denote h)
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T = 2; % time limit (max time)
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f = @(x,t) 0*x.*t; % rhs of the more general equation `u_t - d u_xx = f`
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c1 = @(t) 1+0*t; % _right_ boundary condition
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c2 = @(t) 0*t; % _left_ boundary condition
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u0 = @(x) 0*x; % initial values
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D = 0.5; % diffusion parameter `d` in `u_t - d u_xx = f`
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%uex = @(x,t) cos(x).*exp(t);
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N = 10; % nr. of _space_ discretization points
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K = 200; % nr. of _time_ discretization points
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[x, t, u] = Dirichlet_EA(L, N, T, K, c1, c2, f, u0, D);
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% Report stability condition `D Delta T / (Delta x)^2 > 0.5`
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Delta_T = T / K;
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Delta_x = L / N;
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d = D * Delta_T / Delta_x^2;
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fprintf("Stability Condition: 0.5 >= D * Delta_T / Delta_x^2 = %f\n", d)
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if d > 0.5
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fprintf("-> NOT Stable\n")
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else
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fprintf("-> Stable\n")
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end
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figure(1)
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for ii = 1:K+1 % iterates time
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hold on
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plot(x, u(:, ii)');
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xlim([0 L])
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pause(0.05);
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hold off
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end
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% 3D plot of space solution over time
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space = linspace(0,L,101);
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time = linspace(0,T,201);
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[xx,yy] = meshgrid(time,space);
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%exsol = uex(yy,xx);
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figure(2)
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mesh(t,x,u)
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%figure(2)
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%mesh(xx,yy,exsol)
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%% Eulero forward Mixed BC
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L=2*pi;
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T=5;
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f=@(x,t) 0*x.*t;
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c1=@(t) 1+0*t;
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c2=0;
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u0=@(x) 0*x;
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D=1.1;
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%uex=@(x,t) cos(x).*exp(t);
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N=25;
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K=200;
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[x,t,u]=Mixed_EA(L,N,T,K,c1,c2,f,u0,D);
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figure(1)
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for ii=1:K+1
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plot(x,u(:,ii)');
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xlim([0 L])
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ylim([0 1.5])
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pause(0.02);
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end
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space=linspace(0,L,101);
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time=linspace(0,T,201);
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[xx,yy]=meshgrid(time,space);
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%exsol=uex(yy,xx);
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figure(2)
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mesh(t,x,u)
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%figure(2)
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%mesh(xx,yy,exsol)
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%% Eulero Backward Mixed BC
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L=2*pi;
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T=5;
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f=@(x,t) 0*x.*t;
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c1=@(t) 1+0*t;
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c2=0;
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u0=@(x) 0*x;
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D=1;
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%uex=@(x,t) cos(x).*exp(t);
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N=25;
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K=200;
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[x,t,u]=Mixed_EI(L,N,T,K,c1,c2,f,u0,D);
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figure(1)
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for ii=1:K+1
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plot(x,u(:,ii)');
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xlim([0 L])
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ylim([0 1.5])
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pause(0.02);
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end
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space=linspace(0,L,101);
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time=linspace(0,T,201);
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[xx,yy]=meshgrid(time,space);
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%exsol=uex(yy,xx);
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figure(2)
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mesh(t,x,u)
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%figure(2)
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%mesh(xx,yy,exsol)
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