Singular Jacobian Error Message

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pxg882
pxg882 2012-10-29
编辑: Day Rosli 2016-1-18
Hi all, I'm running the following code:
function M = nonNewtonian(~)
M = bvpinit(linspace(0,10,301),@VKinit);
sol = bvp4c(@VK,@VKbc,M);
figure;
hold all;
plot(sol.x,sol.y(2,:));
plot(sol.x,sol.y(4,:));
hold off;
xlabel('\zeta')
xlabel('\zeta')
hleg = legend('F\prime','G\prime',...
'Location','NorthEast'); %#ok<NASGU>
figure;
hold all;
plot(sol.x,sol.y(1,:));
plot(sol.x,sol.y(3,:));
plot(sol.x,(-1)*sol.y(5,:));
hold off;
xlabel('\zeta')
hleg = legend('F','G','-H',...
'Location','East'); %#ok<NASGU>
function yprime = VK(x,y)
n=1;
yprime = [ y(2)
n^(-1)*((y(2)^(2)+y(4)^(2))^((n-1)/2))^(-1)*((y(1)^(2)-y(3)^(2)+(y(5)+((1-n)/(n+1))*y(1)*x)*y(2))*(1+(n-1)*(y(2)^(2)+y(4)^2)^(-1)*y(4)^(2))-(n-1)*y(2)*y(4)*(y(2)^(2)+y(4)^(2))^(-1)*(2*y(1)*y(3)+(y(5)+((1-n)/(n+1))*y(1)*x)*y(4)))
y(4)
n^(-1)*((y(2)^(2)+y(4)^(2))^((n-1)/2))^(-1)*((2*y(1)*y(3)+(y(5)+((1-n)/(n+1))*y(1)*x)*y(4))*(1+(n-1)*(y(2)^(2)+y(4)^2)^(-1)*y(2)^(2))-(n-1)*y(2)*y(4)*(y(2)^(2)+y(4)^(2))^(-1)*(y(1)^(2)-y(3)^(2)+(y(5)+((1-n)/(n+1))*y(1)*x)*y(2)))
-2*y(1)-(1-n)/(n+1)*x*y(2)];
function res = VKbc(ya,yb)
res = [ya(1);ya(3)-1;ya(5);yb(2)-(yb(5)*yb(1));yb(4)-(yb(5)*yb(3))];
function yinit = VKinit(~)
yinit = [0;0;1;0;0];
but receive the following error message:
??? Error using ==> bvp4c at 252
Unable to solve the collocation equations -- a singular Jacobian encountered.
Error in ==> nonNewtonian at 4
sol = bvp4c(@VK,@VKbc,M);
I'm using n=1 as a test case here. I know the solutions to this system for n=1 but would like to look into the solutions when n is not equal to one. Can anyone explain why I am getting this error?
Any help anyone could give would be greatly appreciated. Thanks!

回答(2 个)

Star Strider
Star Strider 2012-10-29
编辑:Star Strider 2012-10-30
The most likely reason you got the error was that the your boundary values are too large.
I suggest you experiment with:
N = 1;
M = bvpinit(linspace(0,N,301),@VKinit);
and increase N until you again get the error. A value of N that is <10 may not be what you want, but it may be what you have to live with, given finite machine precision. (I did not try to run your code because I cannot determine where the rows of your yprime matrix end. It always helps to format your code. Highlight your code and use the ‘{} Code’ button at the top of the text window to format it.)

pxg882
pxg882 2012-10-30
Thanks for taking the time to look at this. I didn't realise how horribly my code had been displayed on here.
Changing the boundary values is useful you were right. The problem was in the initial conditions I was using.
Thanks for the advice.
  1 个评论
Day Rosli
Day Rosli 2016-1-18
编辑:Day Rosli 2016-1-18
Hello, Hi pxg882. Do you manage to solve your problem? I have the same problem like yours. Is it just by decreasing the value of N?
cc: Star Strider

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