Questions on the symbolic (DSolve, DifferentialRoot) and numerical (NDSolve) solutions of differential equations in Mathematica.

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-3
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0answers
41 views

Mathematica Bug with version 10.4.10 with OSX [on hold]

I have upgraded mathematica to 10.4.10 and OSX El Capitan version 10.11.4. On my desktop I use linux and mathematica version 9. I have a notebook on the desktop that run just fine ( I am solving ...
1
vote
0answers
23 views

Naive question on ODE numerical solving and periodic initial conditions

I have a second-order nonlinear ODE for which I would like to find a numerical solution, with periodic initial (boundary) conditions. Can this be done directly with ...
1
vote
1answer
31 views

NDSolve for complex variables

I am trying to simulate a multiple pendulum system with damping as follows: ...
4
votes
1answer
74 views

DSolve apparently returns wrong symbolic result

Bug introduced in 9.0 and persisting through 10.4.1 I am trying to get Mathematica to calculate the correct solution $x(t)$ of the following ODE: $\dot x = a x(t)+ct^n$ for $a>0$, $n\ge 1$, $c&...
0
votes
0answers
29 views

Question on Poincare section example

I'm trying to make a Poincare section. On the Wolfram Documentation Center they give an example that includes the lines ...
9
votes
1answer
108 views

Memory leak with NDSolve

This is not the first time the question in mentionned (cf in particular this recent question NDsolve memory leak), but there seems to be a serious issue of memory leak - or am I missing something? ...
4
votes
1answer
45 views

How to speed up NIntegrate when using an interpolating function output from NDEigensystem?

I have been working with NDEigensystem in order to find the resonant frequencies of different shaped drums. I would also like the coefficients of the different eigenfunctions so that each of these ...
4
votes
2answers
127 views

NDSolveValue Quality Issue

I'm having trouble with the resolution of the NDSolveValue solution. For example this code from here gives the following on my machine (Windows, Version 10.4.1): (Zoomed in to show detail) ...
0
votes
1answer
59 views

Manipulating of non linear differentials equation

I want to manipulate non linear differential equations $\dot{x}= x + g\, xy\quad \dot{y}= 1-2x^2-g\, y^2$ where g as parameter.but I don't get any curve on display. Plz help me
0
votes
2answers
74 views

Plotting the solution of a Chini differential equation

In DIFFERENTIAL EQUATION SOLVING WITH DSOLVE by D. Kapadia, there is a Chini differential equation : sol = DSolve[x'[t] == 5 x[t]^4 + 3 x[t]^(-4/3), x[t], t] ...
0
votes
1answer
104 views

Solving Partial Differential Equations using NDSolve

I'm trying to solve the following partial differential equation: With the boundary conditions: I could use another way to resolve this, like the finite volume method, but after I solve the ...
0
votes
0answers
105 views
4
votes
1answer
117 views

Solving 2D Laplace equation for irregular boundaries [on hold]

I want to solve Laplace equation in 2D with $x$ and $y$ coordinates with the boundary conditions $V(0,y)=-180$; $V(x,0)=50x-180$; $V(x,6)=50x-180$; $V(453.595-\sqrt{450.05^2 - (y - 3)^2},y)=0$ The ...
0
votes
0answers
49 views

Mathematica treating a system of 1st order nonlinear ODEs as a system of DAEs

I'm trying to use NDSolve to solve a system of 1st order nonlinear ODEs. The system of equations is way too long to post here, but it is in the canonical form: $x_i'(t)=f_i(t,x)$. My problem is that ...
1
vote
0answers
86 views

Differential algebra package in Mathematica

Is there any equivalent of Maple's differential algebra package in Mathematica? In particular, the Rosenfeld-Groebner algorithm has been implemented?
0
votes
2answers
80 views

NDSolve with CUDALink

I am solving a system of non linear differential equations. The time needed to solve them is quite long and I would like to shorten it. Is it possible to send the NDSolve command to be solved by the ...
2
votes
2answers
64 views

Slow evaluation of Recurrence plot data from NDSolve: Performance Tuning

I am trying to use a recurrence plot to pinpoint the location when a system re-visits a previous point in its phase portrait. The system (a thin liquid film) is governed by a non-linear differential ...
1
vote
1answer
60 views

ParametricPlot3D shows an empty box

I'm trying to visualize numerical solution of 4 differential equations (these are the coordinates of a wave function in a quantum mechanical system): ...
6
votes
1answer
166 views
+50

Finite difference method not converging to correct steady state or conserving area?

I am working with the following PDE, which is an advection-diffusion type equation. It describes the movement of a fluid-fluid interface inside an annulus of inner radius $R_1$ and outer $R_2$ under ...
1
vote
1answer
103 views

Not getting the correct solution of a second order ODE [on hold]

This is the original question My code is ...
0
votes
0answers
49 views

Help in controlling NDSolve

I have a system of PDE's with initial and boundary conditions I'm solving using NDSolve. There is one term in the system (v) ...
3
votes
1answer
50 views

Solving biharmonic equation with Mathematica

I would like to solve a biharmonic equation in polar coordinates of the form: $\Delta \Delta \Phi[r,\theta] = r^i cos(j \, \theta) \quad i,j \, \epsilon \, \mathbb{N}_0 $ I know that a solution for ...
0
votes
0answers
35 views

NDSolve is not giving any result nor any error [closed]

I am trying to solve a differential equation for $\psi$, but NDSolve is not giving any result nor any error. Please help me. My function is ...
7
votes
1answer
83 views

NDSolve how to monitor shooting method iteration?

here is a shooting method solution right out of the docs: ...
1
vote
1answer
67 views

Stiffness problem in an NDSolve system. StiffnessSwitching does not help?

I'm trying to solve an ODE system with the NDSolve method. This my ODE system, with the BC and the functions V and dV defined: ...
0
votes
0answers
53 views

Saving the result of a NDSolve

I have solved this diff equation (with no problems): ...
2
votes
1answer
55 views

Problem using Nintegrate and NDsolve

I am going to use Nintegrate to integrate the result of NDsolve and also a Table. How I can ...
0
votes
0answers
93 views

Animating ballistic movement

I was tasked with creating a 3D animation of the movement of a ball through space, while taking into account influences such as the magnus effect, air drag, and rotation. In order for this to happen a ...
7
votes
1answer
76 views

Issuing with ParametricNDSolveValue

I am having a problem with ParametricNDSolveValue[] . let me start with a simple example. Considered following example with constant parameter $a$. ...
2
votes
3answers
110 views

How to integrate numerically the product of result of NDsolve? [closed]

I am going to integrate the product of the results of NDsolve, in fact If x and y are the results as interpolating function, How I can integrate x*y numerically? <...
0
votes
1answer
35 views

NonlinearModelFit error: the function value is not a list of real numbers with dimensions {101} at {a,k,m0} = \ {1.,1.,1.} [closed]

So I'm trying to find a sigmoidal fit for my numerical solutions of these two ODEs but I keep getting an error and I don't know how to get around it. Here's my code: ...
-2
votes
0answers
79 views

Animating Differential Equations [closed]

I was tasked with creating a 3D animation in Mathematica, which aims to describe the movement of a football through space as it's kicked. There are several differential equations regarding this matter ...
0
votes
0answers
39 views

Singularity/Stiff system error

I am after the solutions of the coupled differential equations ...
1
vote
1answer
91 views

To deal with infinity in NDSolve

I just started to learn to use Mathematica, and was trying to obtain an inverse function. Helpful comments lead to the use of NDSolve, but I encountered the problem ...
0
votes
2answers
114 views

Solving a set of nonlinear equations

I am trying to setup and solve a set of nonlinear equations. I keep getting an error. Here is my problem: ...
6
votes
1answer
116 views

How to numerically solve a 1D time-independent Schrödinger equation for two interacting particles

Solving the 1D single-electron time-independent Schrödinger equation has been demonstrated using NDEigensystem here. There, the single-electron Schrödinger equation ...
0
votes
0answers
18 views

Simple heat equation with exponential reaction term [duplicate]

This is the heat equation that i want to solve $${\partial T\over\partial t}={{1\over r^2}{\partial\over \partial r}(r^2{\partial T\over \partial r})+qAC_0exp(-E_a/RT) } \ \ \ 0<t<10, \ \ \ 0<...
0
votes
0answers
64 views

Nonlinear coupled equation (heat equation with source term)

I modeled simple chemical reaction-diffusion equation in spherical region $0\le r\le L$ $${\partial T\over\partial t}={{1\over r^2}{\partial\over \partial r}(r^2{\partial T\over \partial r})+qACexp(-...
0
votes
0answers
53 views

Solving a complicated integro-differential equation

I'm trying to solve the integro-differential equation: $-(1+z) H(z) \frac{d f_{i}}{dz} = J_{i}(E',z) - f_{i} \sum_{j} n_{\nu_{j}} \sigma_{ij}(E',z) + \int_{E'}^{\infty}dE~\sum_{j,k}f_{k} n_{\nu_{j}} ...
0
votes
1answer
63 views

Error message when running NDSolveValue

I am trying to solve a set of differential equations but keep getting an error. See message below "NDSolveValue::ndnum: Encountered non-numerical value for a derivative at t=0" The system that I ...
2
votes
2answers
124 views

How to plot an Eddington-Finkelstein diagram

I need to plot the same thing as what is shown on the third picture of the site below (sorry, I'm unable to poste that picture here) : http://ion.uwinnipeg.ca/~vincent/4500.6-001/Cosmology/...
2
votes
3answers
128 views

NDSolve and differentiation of Abs

I have found several questions about the derivative of Abs and how it is not defined in the complex plane. What I have not found yet is a precise and simple ...
-2
votes
1answer
64 views

Neumann and Dirichlet eigenvalue problem - Eigenfunctions on the square [closed]

I don't know if I am in a good place to ask my question, but I'd like someone to create a visual support for a problem of mathematics. I was wondering what is the fundamental different between a ...
1
vote
2answers
85 views

Stop Integration in NDSolve

The following code executes properly for some choices of initial points and parameter c, but fails for other choices. Could the failure be due to computation outside of the defined t, x, and y ranges? ...
2
votes
2answers
261 views

Ion motion in uniform axial magnetic field and radial electric field [closed]

I'm trying to model an ion's 3D motion in a constant/uniform axial magnetic field and a radial electric field (similar to a cylindrical magnetron, but two positive parallel center electrodes offset by ...
0
votes
0answers
28 views

Evaluating solution from NDSolve at a specific point

sol = NDSolve[{eq, iv}, {f[x, t]}, {x, 0, 1}, {t, 0, 10}]; sol[0,1] I want to evaluate the solution from NDSolve at any given point, but when I do the above, ...
0
votes
1answer
43 views

Speeding up WhenEvent + NDSolve (Performance tuning and handling instabilities)

I am solving a non-linear partial differential equation using NDSolve. The equation models a liquid film on an isothermal solid substrate. As a result of various fluid physics mechanisms such as ...
0
votes
0answers
30 views

Difference between using NIntegrate and Integrate inside NDSolve?

The differential equation I am considering depends on an integral, which I would like to solve with NIntegrate (since it will gets more complicated and thus I have to use NIntegrate later). My code ...
7
votes
2answers
116 views

Bug in NDSolve/WhenEvent?

Bug introduced in v10. I'm fairly sure the following is a bug, and I would normally just report it to WRI. However, this is related to my answer to When using NDsolve, how to determine the ...