bvp4c

Hi

Ive written a matlab code to solve nonlinear set of equations and it stops in the middle of running and says:

??? Error using ==> bvp4c at 252
Unable to solve the collocation equations -- a singular Jacobian encountered

Error in ==> example77k at 49
     Sol = bvp4c(@fun1,@fun1bc,solinit,option) ;

my code is:

ca0 = 0.02*cfin;
cb0 = 0.03*cfin;
cc0 = 5e-4*cfin;

T=550;
solinit = bvpinit(linspace(eps,r,100),[ca0 cb0 cc0 T]);
     Sol = bvp4c(@fun1,@fun1bc,solinit);

function dy = fun1(x,y)
% ca = y(1)
% dca = y(2)
% d2ca = dy(2)

% cb = y(3)
% dcb = y(4)
% d2cb = dy(4)

% cc = y(5)
% dca = y(6)
% d2ca = dy(6)

%T(temprature)=y(7)
%dT=y(8)
%d2T=dy(8)
disp('------------------')
dy = zeros(8,1);
k1 = k10*exp(-E1/y(7))
k2 = k20*exp(-E2/y(7))
ka = ka0*exp(-Ea/y(7))
kc = kc0*exp(-Ec/y(7))

r1 = (k1*y(1)*y(3))/(1+ka*y(1)+kc*y(5))^2
r2 = (k2*y(5)*y(3))/(1+ka*y(1)+kc*y(5))^2
dy(1)=y(2);
dy(2)=r1/Da-(2/x*y(2));
dy(3)=y(4);
dy(4)=((1/2)*r1+(9/2)*r2)/Db-(2/x*y(4));
dy(5)=y(6);
dy(6)=r2/Dc-(2/x*y(6));
dy(7)=y(8);
zigmadeltah=dhr1*r1+dhr2*r2
disp('..............')
fprintf('%e\n %e\n',y,x)
dy(8)=zigmadeltah/k-2*y(8)/x;
end

function bcd = fun1bc(ya,yb)
bcd=zeros(8,1);
bcd(1)=ya(2);
bcd(2)=-Da*yb(2)+kma*(c0(1)-yb(1));
bcd(3)=ya(4);
bcd(4)=-Db*yb(4)+kmb*(c0(2)-yb(3));
bcd(5)=ya(6);
bcd(6)=-Dc*yb(6)+kmc*(c0(3)-yb(5));
bcd(7)=ya(8);
bcd(8)=yb(7)-c0(4);
end

Answer 1

[Walter Roberson]

Try passing in an option set that has a SingularTerms value; see http://www.mathworks.com/help/techdoc/ref/bvpset.html

[Zeynab Mousavi.K]

what you mean?

[Walter Roberson]

Sol = bvp4c(@fun1,@fun1bc,solinit, bvpset('SingularTerms', 12345) )

where 12345 should be the value you want to have used when a singular term is detected. For more information, read the documentation I provided the link to.