希望你们能看懂这个程序。希望008能明白偏微分方程为什么不能那么解。

%jiaozi
function jiaozi
% --------------------------------------------------------------
% parameters
rho_out = 1050;
rho_in = 1050;

k_out = 0.4;
k_in = 0.5;

Cp_out= 3000;
Cp_in = 4000;

thickness_out = 1e-3;
thickness_in = 15e-3;

Tw = 95;
T_ini = 25;
% --------------------------------------------------------------
% mesh:
x_out = [0.00005 0.0001 0.0005 0.001 0.05 [0.1:0.1:0.9], 0.95, 0.99, 0.995,0.999,0.9995,1]*thickness_out;
x_in = [0.00005 0.0001 0.0005 0.001 0.05 [0.1:0.1:0.9], 0.95, 0.99, 0.995,0.999,0.9995,1]*thickness_in;
x_jiaozi = [0, x_out, thickness_out + x_in];

tmax = 600;
t      = linspace(0,tmax,100);

% --------------------------------------------------------------
m = 0;
sol = pdepe(m,@jiaozi_pde,@(x)T_ini,@jiaozi_bc,x_jiaozi,t);
T = sol(:,:,1);
surf(x_jiaozi,t,T)

% --------------------------------------------------------------
function [c,f,s] = jiaozi_pde(x,t,u,DuDx)
if x < thickness_out
k_jiaozi = k_out;
rho_jiaozi = rho_out;
Cp_jiaozi = Cp_out;
else
k_jiaozi = k_in;
rho_jiaozi = rho_in;
Cp_jiaozi = Cp_in;
end
c = rho_jiaozi * Cp_jiaozi / k_jiaozi ;
f = DuDx;
s = 0;
end
% --------------------------------------------------------------
function [pl,ql,pr,qr] = jiaozi_bc(xl,ul,xr,ur,t)
pl = ul-Tw; ql = 0;
pr = 0; qr = 1;
end
end