Check ode15s code to solve a double derivative DE

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I'm pretty much a complete beginner and I've tried modifying an existing code to solve the Gilmore equation. I've attached the code in a txt file as well as a picture of the equations I'm trying to model.
Please let me know if I have to change anything.
  1 Comment
Deepak Gupta
Deepak Gupta on 10 Aug 2020
From line number 47:
H_0 = ; % Initial enthalpy
H_1 = ; % Final enthalpy (?)
These values are not defined. There is syntax error in line 103 also.
dydt = R*y(3)*(1/y(2)/c)+1.5*y(2)^2*(1-y(2)/(3*c)-H*z(2)*(1+y(2)/c) ;

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Answers (1)

Ayush Gupta
Ayush Gupta on 3 Sep 2020
There a couple of problems in the code, I would recommend breaking the function into two functions for ease of understanding. On line 47 there are no values initialized for H_0 and H_1. Also it gives a syntax error in
dydt = [y(3); R*y(3)*(1/y(2)/c)+1.5*y(2)^2*(1-y(2)/(3*c))-H*z(2)*(1+y(2)/c)];
The z variable which is used here is undefined or not initialized. To have a function call to get the equation inside the ode15s function check the documentation of ode15s and examples on how to use it here.

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