I want to solve 7 coupled equations.I use method of line(MOL) and discrete the equation in Length and radius and convert them to a system of ODEs in time.and use ode15s to solve them in MATLAB. But an error occur:
Warning: Failure at t=5.422028e-006. Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.355253e-020) at time t.
It means that equations are too stiff. How can i solve them? Is there another method? The equations are true.I am sure.