Filter löschen
Filter löschen

Singular Jacobian Error Message

3 Ansichten (letzte 30 Tage)
pxg882
pxg882 am 29 Okt. 2012
Bearbeitet: Day Rosli am 18 Jan. 2016
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!

Antworten (2)

Star Strider
Star Strider am 29 Okt. 2012
Bearbeitet: Star Strider am 30 Okt. 2012
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 am 30 Okt. 2012
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 Kommentar
Day Rosli
Day Rosli am 18 Jan. 2016
Bearbeitet: Day Rosli am 18 Jan. 2016
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

Melden Sie sich an, um zu kommentieren.

Tags

Community Treasure Hunt

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

Start Hunting!

Translated by