How to solve ODE's and find m(t) using matlab? Urgent!!

1 次查看(过去 30 天)
Here is the given ODE for which I need a solution:
Please help me on how to do this!!!

采纳的回答

Star Strider
Star Strider 2014-7-25
编辑:Star Strider 2014-7-25
Use ode45. It’s five lines of code, including the plot:
mdot = @(t,m) sqrt(2E+5.*((1+(0.4-m)./0.5).^-1.4 - 1));
[t,m] = ode45(mdot, [0 1], 0.001);
figure(1)
semilogy(t, real(m), '-b', t, imag(m), '-g')
grid
  3 个评论
Star Strider
Star Strider 2014-7-26
Since I did’t have other information, I chose m(0)=0.001 and ran it from [0 1] in time. With your m(0)=0.4 and time span [0 0.5] the call to ode45 is:
[t,m] = ode45(mdot, [0 0.5], 0.4);
and the entire code is now:
mdot = @(t,m) sqrt(2E+5.*((1+(0.4-m)./0.5).^-1.4 - 1));
[t,m] = ode45(mdot, [0 0.5], 0.4);
figure(1)
plot(t, m, '-*b')
grid
axis([xlim 0 0.5])
With the square root, I’m somewhat surprised that there aren’t two solutions, for instance ±0.4 but the routine produces only one. Yours is a nonlinear equation, and the Symbolic Math Toolbox cannot solve it. (I have it, and I tried that to see what it would do. There is no analytic solution.)
The output doesn’t change from the initial conditions, and is uniformly 0.4 from 0 to 0.5.

请先登录,再进行评论。

更多回答(0 个)

类别

Help CenterFile Exchange 中查找有关 Symbolic Math Toolbox 的更多信息

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by