Defining boundary condition for pde for pdepe function

Question

vibha s 2016-7-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/297199-defining-boundary-condition-for-pde-for-pdepe-function

回答： jose luis huayanay villar 2020-6-22

I have got a pde as show in the function [c,f,s]. Unable to get the solution for the equation and not able figure out the mistake in boundary condition

L = 200;                 
s1 = 0.5; %equal to k at x=0               
s2 = 0;                  
T = 4;                   
qr = 0.218;               
f = 0.52;                
a = 0.0115;              
n = 2.03;                
ks = 31.6;               
x = linspace(0,L,100);
t = linspace(0,T,25);
options=odeset('RelTol',1e-4,'AbsTol',1e-4,'NormControl','off','InitialStep',1e-7)
u = pdepe(0,@unsatpde,@unsatic,@unsatbc,x,t,options,s1,s2,qr,f,a,n,ks);

I'M STRUCK AT THIS POINT. Following gives the editor .m files

% -------------------------------------------------------------------------
function [c,f,s] = trial1(x,t,u,DuDx)
global k n qr a ks p
c=1;
f = k*((DuDx)+1);
s = 0;
m =0.51;
q=qr+(p-qr)*(1+(-a*u)).^-m;
k=ks*((q-qr)/(p-qr))^0.5*(1-(1-((q-qr)/(p-qr))^(1/m))^m)^2;
% -------------------------------------------------------------------------
function u0 = unsatic(x,s1,s2,qr,f,a,n,ks)
u0 = 200+x; 
% -------------------------------------------------------------------------
function [pl,ql,pr,qr] = unsatbc(xl,ul,xr,ur,t,s1,s2,qr,f,a,n,ks)
pl = 0; 
ql = 1; 
pr = ur(1);
qr =0;

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Answer 1

Torsten 2016-7-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/297199-defining-boundary-condition-for-pde-for-pdepe-function#answer_229774

在 MATLAB Online 中打开

1. "trial1" is not part of the list of functions you call pdepe with.

2. You will have to include s1,s2,qr,f,a,n,ks in the parameter list for "trial1".

3. in "trial1", you use k before you calculate it.

4. In unsatbc, you set as boundary conditions

u=0 at x=L

and

du/dx = -1/k at x=0

I don't know if this is what you want to set.

Best wishes

Torsten.

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vibha s 2016-7-26

Hi thanks for the suggestions,trying to extract the value of pL,qL and qR,pR in boundary condition code file. warning says error at intermediate points