solution of coupled first order odes numerically

Question

Sattik Basu 2018-6-20

评论： Sattik Basu 2018-6-26

eqn1 = coeff1*var1 + coeff2*diff(var1) + coeff3*var2 +coeff4*diff(var2) == 0;

eqn2 = coeff5*var1 + coeff6*diff(var1) + coeff7*var2 +coeff8*diff(var2) == 0;

bc1 = var1(0) == const1

bc2 = var2(0) == const2

i have all the coeffs defined as function handles. dsolve doesnt give solution as no explicit solution is present. How do i solve them numerically?

This can be easily done in Mathematica with NDSolve. However, i cant seem to think how i can appl oe45 or whatever is needed.

Answer 1

Torsten 2018-6-21

Use the mass matrix option of the ODE solvers.

Or explicitly solve your equations for diff(var1) and diff(var2) (2 linear equations in 2 unknowns).

Best wishes

Torsten.

Sattik Basu 2018-6-26

I ended up converting the system in a matrix form and solved them hassle free. This worked great with initial values.