# Questions tagged [ode]

Ordinary Differential Equations (ODEs) contain functions of only one independent variable, and one or more of their derivatives with respect to that variable. This tag is intended for questions on modeling phenomena with ODEs, solving ODEs, and other related aspects.

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### Solving chain of ODE in Julia

I am solving two different ODE whose solutions need to be matched. I am currently doing this by hand, which works great, but I would like to automatise this process. The second ODE takes one of its ...
0answers
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### Solving this ODE on MATLAB

I have the following ODE - $\frac{dn}{dt} = \frac{1-n}{A} - \frac{u(t)}{B}n , -30\leq t\leq30, n(-30)=1$ where $A,B$ are constants and $n = n(t)$. I can solve this ODE analytically and get an ...
0answers
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### Solving PDEs: What is the best way to deal with non-banded/dense jacobians?

I have a system of PDEs describing atmospheric chemistry and transport. I use finite-differences to make my system of PDEs into a system of ~10,000 ODEs. I then integrate the ODEs forward in time with ...
0answers
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### scipy solve_ivp with adaptive solution

I am struggling to understand how scipy.solve_ivp() handles errors in a system of ODE. I have a complex systems of ODE with very large varying time-scales, for which my state "y" is composed ...
2answers
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### numerical solution for differential equation

I have these 3 equations and i want to solve them with numerical methods. so I am using scipy library but I don't know how to solve 3 equations together. R, g, sigma and density are constants. \begin{...
1answer
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1answer
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### Preferred application for shooting method

Every now and then there are questions asked in this site related to the shooting method for boundary value problems (see 1, 2, 3). Nevertheless, in some of the cases that I have seen here, the ...
0answers
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### Path constraints for state variables - fmincon, ODE45

My problem lies in constraining state variables (look for 23,24,25). I am currently using ODE45 to solve equations and fmincon to find best control variable.How would you go about solving this? Here ...
1answer
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### Problem with solving coupled ODE and DAE equations with mass matrix (Error using daeic12 (line 77) This DAE appears to be of index greater than 1)

I am trying to solve 6 ODE equations coupled with 1 DAE one. The ODE equations have been discritized in space domain and ode15s MATLAB solver is used to solve the equations in time domain. I have ...
0answers
123 views

### Conservation of energy test for 2-body problem

I'm trying to implement a C++ code for the evaluation of the solution of an N-body system of ODE. I've started with a 2-body problem just to set the methods ...
1answer
58 views

### (2) Trying to model a simple second order ODE: Why time-step smaller is not better

This question is related with this other question: Trying to model a simple second order ODE. On this other question, I get some useful comments on why the simulations are so terrible. However, I have ...