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# Please help! pdepe does not stop!!

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Hüseyin Cagdas Yatkin on 17 Dec 2019
Answered: Guru Mohanty on 23 Jan 2020
Hello guys, I trying solve below question with pdepe and whe I run the code as mantioned in the below code, it never stop working.
v = 49 680 m/day
kd = 0.24 1/day
ks = 58,8 m/day
h = 5 m
C(t = 0,x) = 13.75 mg/L initial condition
C(t, x = 0) = 13.75 mg/L
C(t, x = 1000m) = 10.05 mg/L
clc
clear
x = linspace(0,1000,1000);
t = linspace(0, 7, 28);
m = 0;
sol = pdepe(m, @pde,@pdeic,@pdebc,x,t);
u = sol(:,:,1);
sol(1000,:);
plot(x, sol(1000,:))
function [c, f, s] = pde(x, t, C, dCdx)
c = 1/(0.575*24*3600);
f = C;
s = (0.24+2.45*24/5)/(0.575*24*3600)*C;
end
function u0 = pdeic(x)
u0 = 13.75;
end
function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t)
pl = ul - 13.75;
ql = 0;
pr = ur - 10.05;
qr = 0;
end

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### Answers (1)

Guru Mohanty on 23 Jan 2020
Hi, I understand you are trying to solve this partial differential equation. You can do this by using pdepe. Here is a sample code.
clc
clear all;
x = linspace(0,1000,1001);
t = linspace(0, 7, 28);
m = 0;
sol = pdepe(m, @pde,@pdeic,@pdebc,x,t);
val=sol(28,:);
figure
surf(t,x,sol');
figure
plot(x,val);
function [u, f, s] = pde(x,t,u,dudx)
u = 1/(0.575*24*3600);
f = u;
s = (0.24+2.45*24/5)/(0.575*24*3600)*u;
end
function u0 = pdeic(x)
u0 = 13.75;
end
function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t)
pl = ul - 13.75;
ql = 0;
pr = ur - 10.05;
qr = 0;
end

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