Unable to meet integration tolerances

1 回表示 (過去 30 日間)
Nishant Gupta
Nishant Gupta 2020 年 7 月 12 日
コメント済み: Bill Greene 2020 年 7 月 12 日
I am using the 'pdepe' solver in Matlab but I get this error-
Warning: Failure at t=1.000000e+00. Unable to meet integration tolerances without reducing the step size below the smallest value allowed (3.552714e-15) at time t.
> In ode15s (line 653)
In pdepe (line 289)
In differential (line 5)
Warning: Time integration has failed. Solution is available at requested time points up to t=1.000000e+00.
> In pdepe (line 303)
In differential (line 5)
Here's the code I have-
clc
x = linspace(0,10,20);
t = linspace(1, 1000, 100);
m = 0;
sol = pdepe(m, @pde1pde, @pde1ic, @pde1bc, x, t)
function [c,f,s] = pde1pde(x, t, u, dudx)
rho = 906;
Cp = 0.4365;
MW = 104.15;
dH = -17800;
k = (1.22-0.002*u)/36;
xp = 1-x;
A0 = 1.964*(10^5)*exp(-10040./u);
A1 = 2.57-5.05*u*(10^(-3));
A2 = 9.56-1.76*u*(10^(-2));
A3 = -3.03+7.85*u*(10^(-3));
A = A0*exp(A1*(xp) + A2*(xp^2) + A3*(xp^3));
c = (rho*Cp)/k;
f = dudx;
s = (((rho/MW)*x)^(2.5))*A*(-dH)/k;
end
function u0 = pde1ic(x)
T0 = 20 + 273.15;
u0 = T0;
end
function [pl, ql, pr, qr] = pde1bc(xl, ul, xr, ur, t)
pl = 0;
ql = 1;
pr = 0;
qr = 1;
end
I have tried changing the arguements of t = linspace(1,1000, 100) but I get always get the same error. The solution is provided only for the first value of the vector t and it is equal to T0 irrespective of the value of t. Any hellp is appreciated

回答 (1 件)

Bill Greene
Bill Greene 2020 年 7 月 12 日
Your equations have a fundamental error. Just calculate the "s" term along the length at the initial temperature and the problem will be obvious.
  2 件のコメント
Nishant Gupta
Nishant Gupta 2020 年 7 月 12 日
I got my mistake. There are actually 4 variables in the system- "z" is the spatial dimension, "t" is the time, "u" is the temperature and the "x" I have used in defining the equations above is actually the mass fraction and not the length.
Seeing that there are 4 variables now, are there any methods in Matlab that would allow me to solve this system?
Thanks!
Bill Greene
Bill Greene 2020 年 7 月 12 日
I suggest you edit your question to describe your equations in mathematical form, defining all symbols, and including boundary and initial conditions.

サインインしてコメントする。

カテゴリ

Help Center および File ExchangeEigenvalue Problems についてさらに検索

Community Treasure Hunt

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

Start Hunting!

Translated by