Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.



System of secondorder nonlinear ordinary differential equations
Posted:
Nov 14, 2012 1:50 AM


Hello,
I'm new to this forum and also to Mathematica, so please treat me gentle :)
I would solve numerically the velocity profiles of a rotating disk. Thefore following system must be solved for the 3 (nondimensional) unknown velocityfunctions F(eta), G(eta) and H(eta), with eta=nondimensional wall distance (see "Boundary Layer Theory" by H. Schlichting):
2F+H'=0 F^2+F'*HG^2F''=0 2F*G+H*G'G''=0
with the follwing boundary conditions:
F(x=0)=0 G(x=0)=1 H(x=0)=0 F(x>\inf)=0 G(x>\inf)=0
I tried to implement the problem into Mathematica with the numerical solver :
NDsolve[{2*F[eta] + H'[eta] == 0, (F[eta])^2 + F'[eta]*H[eta]  (G[eta]^2  F''[eta] == 0, 2*F[eta]*G[eta] + H[eta]*G'[eta]  G''[eta] == 0}, {F[0] == 0, G[0] == 1, H[0] == 0, F[1000000] == 0, G[1000000] == 0}, {eta, 1000000}]
Plot[Evaluate[{F[eta], G[eta], H[eta]} /. s], {eta, 0, 5}, PlotStyle > Automatic]
I did not arrive to any solution but to many many errors. If you could give me any hint I would be really thankful!
Best regards



