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How to Solve a system of coupled ODEs in...

Asked: Mayo_Kun 5 Product: Maple 2016

September 08 2019

1 4

Hello,

I am trying to solve a set of coupled ODEs in the following code (ODE_Prob.mw). But I am getting an error.

Please, what does this error mean and what is the solution.

Thanks in advance.

restart; PDEtools[declare](f(eta), prime = eta, theta(eta), prime = eta); Digits := 16; inf := 9

(1)

equ1 := (2*n+1)*f(eta)*(diff(theta(eta), eta))/(2*(n+1)) = (diff(theta(eta), eta, eta))/Pr^(2/(n+1))

(2*n+1)*f(eta)*(diff(theta(eta), eta))/(2*n+2) = (diff(diff(theta(eta), eta), eta))/Pr^(2/(n+1))

(2)

equ2 := (1/2)*(diff(f(eta), eta))^2-(2*n+1)*f(eta)*(diff(f(eta), eta, eta))/(2*n+2) = -n*(diff(f(eta), eta, eta))^(n-1)*(diff(f(eta), eta, eta, eta))+theta(eta)

(3)

indets(equ1);

${Pr, eta, n, Pr^(2/(n+1)), diff(diff(theta(eta), eta), eta), diff(theta(eta), eta), f(eta), theta(eta)}$

${eta, n, (diff(diff(f(eta), eta), eta))^(n-1), diff(diff(diff(f(eta), eta), eta), eta), diff(diff(f(eta), eta), eta), diff(f(eta), eta), f(eta), theta(eta)}$

(4)

(5)

equ1;

(6)

SolP1 := dsolve({Bcs, equ1, equ2}, numeric); SolP1(0); SolP1(inf)

Error, (in dsolve/numeric/BVPSolve) unable to store '-.4744942626692375+1.460343180701223*I' when datatype=sfloat

(7)

p1 := plots:-odeplot(SolP1, [eta, f(eta)], 0 .. inf); p2 := plots:-odeplot(SolP1, [eta, theta(eta)], 0 .. inf); p3 := plots:-odeplot(SolP1, [eta, diff(f(eta), eta)], 0 .. inf); plots:-display(Array([p1, p2, p3]))