Need Help Solving System of ODEs

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Akrant Rai
Akrant Rai il 18 Nov 2021
Commentato: Akrant Rai il 19 Nov 2021
close all; clear all; clc
I wanted to solve these 4 ode(s) and was trying to use ode45, but the output is not what I was expecting, the v is supposed to decrease but it was increasing, the gamma was also supposed to become more negetive but it remained constant. Any idea about where I must be going wrong? Thanks in advance!
g=9.81;
z0=10000;
R=6378000;
h0=(R*z0)/(R+z0);
for z=1:10000
h(z)=(R.*z)./(R+z);
rho0=0.4135;
H=8500;
rho=rho0.*exp((h0-h)./H);
end
v0=450;
gamma0=-20;
m0=2500;
T=15000;
Isp=300;
dodt=@(t,W)[(-g*sin(W(2)))-(T/W(4));(-g/W(1))*cos(W(2));W(1)*sin(W(2));-T/(g*Isp)];
[t,W]=ode45(dodt,[0,21.93],[v0,gamma0,z0,m0])
v=W(:,1);
gamma=W(:,2);
z=W(:,3);
m=W(:,4);

Risposte (1)

Alan Stevens
Alan Stevens il 18 Nov 2021
You haven't included the first term on the right-hand side of your equation for dV/dt, nor for dgamma/dt.
  5 Commenti
Alan Stevens
Alan Stevens il 19 Nov 2021
I did mean that - I misread the term! So, I don't see anything else wrong with the equations! You will need to check they are derived correctly, and that you have used the right data.
Akrant Rai
Akrant Rai il 19 Nov 2021
Alright. I will check the physics again to make sure that is right. Thank you for all the help!

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