Solving one non linear differential equation

Hi,

I have a question involving solving a NLDE. The equation is of the form: dx/dt = -C1*(C2+C3*x^(0.25))*x

I would like to solve this equation in MATLAB, and get x(t). I first tried to do this with a simple dsolve, but it says solution = 0.

Main code i used: solution = dsolve('Dx = ((-k*A)/(L*m*Cp))*(0.68+Const*x^(0.25))*x')

(all variables other than x are constants i have defined above.)

Is dsolve the right choice for this equation? I want to try ODE45 but i don't know how (syntax-wise) define this function so that i can input it in ODE45.

Can anyone make a suggestion? Maybe use of implicit ODE's?

Kind regards, Wim

Answer 1

[Star Strider]

See if this works for you:

DX = @(t,x) ((-k.*A)./(L.*m.*Cp)).*(0.68+Const.*x.^(0.25)).*x;

then call it as:

[T,Y] = ode45(DX, [linspace(0, 10, 1000)], [0.1]);

Since DX is set up as an anonymous function, you don't have to define it as a separate program file. It will also be able to access k, A, and all the other variables in your workspace.