mecej4
Posts:
3
Registered:
1/19/11


Re: Help with bvp4c
Posted:
Sep 18, 2013 6:33 PM


On 9/15/2013 6:31 PM, Midhun wrote: > Hi all, > > I have a 2nd order equation given by: > > C" + i/(C+ r) *( C/(C+r)  1 ) C'  k* C = 0 > > where C = C(x), > i, r,k are constants. > > Boundary conditions: > C(0) = 1; > C'(1) = 1/(1 + r/C). > > I was trying to use bvp4c for this problem by converting them to a set > of ODEs, but couldn't make out how to specify the 2nd boundary condition. > > Set of ODEs: > > C' = P > P' = i/(C+r) * (C/C+r  1)*P +k*C > > BCs : C(0) = 1; > P(1) = i/(1+r/C) > > My code: > > solinit = bvpinit([0,1],[0,0]); > sol = bvp4c(@deriv,@bcs,solinit); > plot(sol.x,sol.y(1,:),'bx',sol.x,sol.y(2,:),'gx'); > > % > > function dYdx = deriv(x,Y) > i = 1;r = 1; > k = 1; > dYdx = zeros(2,1); dYdx(1) = Y(2); dYdx(2) = i/(Y(1)+r) * > (Y(1)/(Y(1)+r)  1)*Y(2) + k * Y(1); > > % > > function res = bcs(ya,yb) > i = 1; > r = 1; > res = [ ya(1)  1 ???? ]; > > Could anyone help me on I can specify the 2nd B.C which is a function of > C ? > Thanks in advance...
In your notation, yb(1) and yb(2) in function "res" stand for C(x=1) and C'(x=1). Hence, you should have
res = [ ya(1)  1; yb(2)  1/(1 + r/yb(1)];
HTH  mecej4

