help plotting at x=0 dt/dx=0

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Nataly Almasri
Nataly Almasri on 3 Oct 2020
Answered: Ashish Mishra on 13 Oct 2020
This is the code the pipe that i am coding and is insulated and i need to incorporate that at x=0 dt/dx=0 but i am having trouble where to put it and how to put it
my graph is suppose to be flipped doing the at x=0 dt/dx=0
clear all
close all
Tinf=300;
Tb=400;
n=25;
L=1; %m
nsquare=25; %/m^2
dx=L/n;
aw=1/dx;
ae=aw;
ap=aw+ae+nsquare*dx;
A=zeros(n,n);
b=zeros(n,1);
for i=2:n-1 % number of equations
A(i,i)=ap; %Ap
A(i,i-1)=-aw; %Aw
A(i,i+1)=-ae; %Ae
b(i)=nsquare*dx*Tinf;
end
i=1
A(i,i)=3/dx+nsquare*dx; %Ap
A(i,i+1)=-1/dx; %Ae
b(i)=2*Tb/dx+nsquare*dx*Tinf;
i=n
A(i,i)=1/dx+nsquare*dx; %Ap
A(i,i-1)=-1/dx; %Aw
b(i)=nsquare*dx*Tinf;
T=linsolve(A,b)
hold on
figure(1)
plot(T)
title('Phi as function of grid point')
axis([0 n 0 100])
xlabel('i') % x-axis label
ylabel('Phi') % y-axis label
T_BC=zeros(n+2,1);
T_BC(1)=Tb;
for i=2:n+1 % number of equations
T_BC(i)=T(i-1);
end
T_BC(n+2)=T_BC(n+1);
y(1)=0;
y(2)=dx/2;
y(n+1)=L-dx/2;
y(n+2)=L;
for i=3:n % number of equations
y(i)=y(i-1)+dx;
end
figure(2)
plot(y,T_BC)
title('Phi as function of x')
xlabel('x') % x-axis label
ylabel('T') % y-axis label

Answers (1)

Ashish Mishra
Ashish Mishra on 13 Oct 2020
The condition, dt/dx=0, is already included in the code because it implies that at that given x ,T(i)=T(i-1) and flip function can be used to flip the T matrix , so that the plot of T will be flipped.

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