pdepe solver for spherical coordinates

2023 3 28
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更新时间：2023 3 28
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I am using the heat conduction equation for solid which has the source term to enter the code in Matlab. But even changing any values of s the plot is not chnaging atall. What could be the problem?

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Torsten
Torsten 2023-3-28
We don't know since we don't know the code you are using.
John D'Errico
John D'Errico 2023-3-28
Probable user error. A mistake you made in either running or writing the code.
Think about it. Read your question, as if you were yourself trying to provide help. We are expected to know what you did wrong, based only on being told that when you change the value of s, nothing happens. What is s? Now think about how we should know the answer to your question from that little information.
Seriously. Do you want a better answer? You need to provide more information. You might show the code you wrote, and hope someone will be willing to dive into it. If you do that, then you also need to show the actual equations you are trying to solve, so that same person might be able to verify if you implemented them properly.
Ishani Prachchhak
Ishani Prachchhak 2023-3-28
m=0; %for spherical symmetry
egen=1.234e19;%Energy absorbed per unit volume(W/m^3)
k=5.9;%(W/m.K)
Tinfi=296;
x=linspace(0,15e-9,20); %m
t= linspace(0,1e-10,20);
%x=r u=T
sol=pdepe(m,@pdefun,@pdeic,@bc,x,t);
u=sol(:,:,1);
surf(x,t,u);
xlabel('r');
ylabel('t');
function [c,f,s]= pdefun(x,t,u,dudx);
alpha=7.9e-9;%(m^2)/s
egen=1.12157e-05;
k=5.9;%(W/m.K)
c=1/alpha;
f=(dudx)*x^-2;
s=egen/k;
end
function T0=pdeic(x)
T0=296;
end
function [pl,ql,pr,qr]= bc(xl,ul,xr,ur,t)
k=5.9;%(W/m.K)thermal conductivity
x=15e-9;
A=4*3.14*(x)^2;%Area
pl= 0;
ql= 1;
pr=1.234e19;
qr=-2*k;
end
Ishani Prachchhak
Ishani Prachchhak 2023-3-28
I am trying to solve for constant conductivity equation using pdepe.
Torsten
Torsten 2023-3-28
编辑：Torsten 2023-3-28
You set up the following problem:
1/alpha * du/dt = d/dx ( 1/x^2 * du/dx) + egen/k
u(t=0) = 296
1/x^2 * du/dx = 0 at x=0
1.234e19 - 2*5.9/x^2 * du/dx = 0 at x = 15e-9.
Is this really what you try to solve ?
If not: please include equation, initial and boundary conditions.

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