Clear Filters
Clear Filters

Thomas algorithm - tridiagonal matrix

20 views (last 30 days)
Is there any other way to code and solve the tridiagonal matrix? the idea would be to try to get the plot shown. Matlab beginner, so, no sure how to do it. Any help will be greatly appreciated. Thanks
clear
cm=1/100;
delta = 1*cm;
nu=1e-6;
Uinf=1;
H=2*delta;
y=linspace(0,H,40);
u=Uinf*erf(3*y/delta);
dy=mean(diff(y));
dx=100*dy;
Q=nu*dx/Uinf/dy^2;
a=-Q;
c=-Q;
b=1+2*Q;
N=length(y)-2;
M = diag(b*ones(1,N)) + diag(c*ones(1,N-1),1) + diag(a*ones(1,N-1),-1);
%Constant Ue
Ue = @(x) Uinf;
u = u(2:end-1);
x=0;
uall=[0,u,Ue(x)];

Accepted Answer

Torsten
Torsten on 2 Mar 2023
Edited: Torsten on 2 Mar 2023
clear
cm=1/100;
delta = 1*cm;
nu=1e-6;
Uinf=1;
H=2*delta;
y=linspace(0,H,40);
u=Uinf*erf(3*y/delta);
dy=mean(diff(y));
dx=100*dy;
Q=nu*dx/Uinf/dy^2;
a=-Q;
c=-Q;
b=1+2*Q;
N = length(y);
M = diag(b*ones(1,N)) + diag(c*ones(1,N-1),1) + diag(a*ones(1,N-1),-1);
M(1,:) = [1,zeros(1,N-1)];
M(end,:) = [zeros(1,N-1),1];
%Constant Ue
Ue = @(x) Uinf;
u = u(2:end-1);
x=0;
uall=[0,u,Ue(x)];
sol = M\uall.';
plot(y,sol)
grid on
  5 Comments
Torsten
Torsten on 2 Mar 2023
You can assign values to certain elements in a matrix by using a loop. But if the above line to define M is correct, it's elegant, isn't it ? Why do you want to define it differently ?
Cesar Cardenas
Cesar Cardenas on 2 Mar 2023
Right thank you, just wanted to have a different version. Thanks

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!