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

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3
votes
1answer
114 views

DSolve not returning a rule

I am trying to solve a PDE, but the DSolve is not returning a rule. How exactly can I get Mathematica to yield a solution? ...
0
votes
0answers
70 views

Flux continuity with NDSolve

When NDSolve is applied to model mass diffusion (or heat flow) through different materials, is the continuity of flux condition automatically satisfied at the ...
0
votes
0answers
113 views

What is the largest system of PDE you have solved with Mathematica?

I need to solve a system of partial differential equations. In the simplest case it consists of 2000 of PDE equations. In the most complex situation it consists up to 1 million of such equations. ...
7
votes
1answer
227 views

mathematica 10 not showing numerical solution of differential equations?

I just got the new mathematica version 10 and tried to solve the following system of differential equation. $$r^2\frac{d^2f}{dr^2} = 2f(1-f)(1-2f)+\frac{r^2}{4}h^2(f-1)$$ ...
-1
votes
1answer
99 views

Find $r$,in terms of variables $U$ and $V$

I want to solve this equation, for $r$: ...
0
votes
0answers
97 views

Solving for a coordinate transformation for a rank 2 tensor

I am working on a project in general relativity, and I have a metric or rank 2 tensor $g_{ab}$ of the form, $$g =\left( \begin{array}{ccccc} f(x^a) & 0 & 0 & 0 & 0\\ 0 & -f(x^a) ...
-2
votes
1answer
87 views

Ordinary Differential Equation Question [closed]

I was wondering whether someone might be able to point me in the right direction for this ODE that I am trying to solve? It is: $$\frac{du}{dx} = \frac{x}{s}-\frac{1}{2}-\frac{u}{x}$$ with $s$ ...
1
vote
1answer
202 views

Locating Periodic Orbits

Here is the code for the numerical integration of an orbit. First the module for the definition of the equations of motion. ...
2
votes
0answers
136 views

How to control pedestrians to enter the simulation region with random functions?

I am working on simulating crowds of a cross-typed region, given that pedestrians entering from 4 gates of north, east, west and south, ...
0
votes
0answers
89 views

Solving a system of ODEs with DSolve

I am trying to solve a system of ODEs using DSolve ...
1
vote
0answers
99 views
1
vote
1answer
87 views
0
votes
2answers
59 views

trouble with adding a legend to a plot

I am having trouble with adding a legend to a plot. this is my code,I tryed to use serval things,like ...
1
vote
2answers
339 views

NDSolve with Explicit, Implicit Euler and Trapezoidal method

I am using Mathematica 9.0 both on Linux and Windows and I would like to integrate the Van der Pol equation numerically using various techniques such as Explicit and Implicit Euler and Trapezoidal ...
7
votes
3answers
348 views

How to prevent instability blow up in NDSolve?

I have the following code to solve a PDE: ...
0
votes
0answers
148 views

Issue in NDSolve and unknown error

I try to solve a simple BVP: $A {v}''(t)+B v(t)=f(t)$ where $A, B$ — $5\times 5$ matrices, $f(t)$ — 5-dimentional vector-function with the use of NDSolve. Each component of $f(t)$ is a combination ...
2
votes
0answers
122 views

DSolve versus DSolveValue [closed]

I've just discovered the new command DSolveValue in Mathematica 10. Is this new command now the preferred instead of DSolve? Is it the better command to teach to students? Same question for ...
5
votes
2answers
171 views

Implement functions that depend on previous value in NDSolve

I want to numerically solve a system of differential equations in Mathematica, say for example $\frac{dx}{dt} = f(x,y,t) \\ \frac{dy}{dt} = g(x,y,t)$ for $x(t), y(t)$. However, the functions depend ...
2
votes
1answer
276 views

NDSolve and maximum number of steps reached

I am newbie at Mathematica but I need to solve differential equation so I took my chances and tried to use this powerful tool to solve this equation: $$\frac{d}{dx}\left([\cos(2\pi ...
1
vote
1answer
197 views

Plot multiple solutions of a system of differential equations with different values of constant c by using NDsolve

I am traying to solve system of differential equations with different values of constant c then plot the solution with different values of the constant c. where c= 2.2758, 2.04822, 1.82064, 1.59306, ...
0
votes
1answer
91 views

To get a certain value of NDsolve of the solution [closed]

I need to solve the differential equations for different values. Once it is solved I want to take, for example, x[29] for each initial condition and plot it as a function of this initial conditions. I ...
5
votes
0answers
151 views

Alternatives to FiniteElement as Spatial Discretization Method for NDSolve

Finite Element Programming: [...] It is possible to skip this section and continue with the discretization stage and make use of the initialized data structures ...
6
votes
2answers
207 views

RegionPlot from NDSolve

I am having quite a headache using RegionPlot to see the region of acceptance of certain coupled differential equation. I shall elaborate and try to be as ...
4
votes
2answers
256 views

Solving a discontinuous differential-algebraic equation system for plasticity behaviour

I need to solve a discontinuous equation which is typical in theory of plasticity. For a simple case I get the following equation system (reformulated for numerical implementation): $s(t) = ...
3
votes
1answer
214 views

Trouble understanding NeumannValue and Inactive/Formal PDEs

I read all documentation about the Finite Element Method in Mathematica 10, and I read some questions here, but I'm still unable to properly understand how to use the ...
1
vote
2answers
168 views

Help to numerically solve ODE

http://math.stackexchange.com/questions/912076/time-period-of-ode Trying to numerically compute and compare the time period of an oscillation with the analytical solution suggested by Robert Israel. ...
5
votes
3answers
145 views

Trouble Discretizing a ParametricRegion; Joukowsky Map and Wing Profiles

I'm trying to compue a mesh of full 2D region delimited by the a circle transformed with a Complex map. ...
1
vote
1answer
76 views

Strange constants in a PDE solution by DSolve

I'm solving the following PDE: DSolve[F''[ξ] + (Ω^2 - M^2 Exp[2 α ξ]) F[ξ] == 0, F[ξ], ξ] And Mathematica gives a general solution in terms of modified Bessel ...
10
votes
1answer
364 views

representation of custom deformation on a meshgrid

I am trying to represent 2D deformations on a rectangular grid. In Mathematica 10, there is a method to solve the elastic differential equations and then represent the deformation as presented here: ...
0
votes
0answers
75 views

EquationTrekker PropertyValue errors

In Mathematica 10.0.2, the basic example for EquationTrekker in the documentation is: ...
1
vote
0answers
265 views

NDSolve: Equation with interpolating function [closed]

I have a question regarding DSolve and NDSolve functions in Mathematica 10. For instance, I'd like to solve an ODE: ...
5
votes
1answer
125 views

Solve a differential equation with an integral inside?

I am trying to solve this differential equation in Mathematica: y'[t]+integral from 0 to t of y[x]dx =e^(-t) where y[0]=0. Is this possible?
10
votes
2answers
925 views

Water Hammer - Numerically solving system of PDEs

I'm trying to use Mathematica to solve the water hammer effect. ...
0
votes
1answer
98 views

Parametric Plotting

I am trying to make a parametric plot of the x and y displacements of a vibration problem. When trying to plot the parametric curve won't show up.
0
votes
0answers
61 views

when DSolve fails

I am doing this mathematical problem $c*G_{vv}+ d*G_{u} + e*G_{v} +f*G=0$, where $c, d, e$ and $f$- are constant coefficients. I already know that this is second order PDE and we classify it by ...
0
votes
0answers
163 views

Time-dependent mesh deformation

I want to display the result of a deformation with a mesh, but I solved the deformation with a time dependency. So I have two functions: uxsol[t,x,y] and ...
3
votes
1answer
168 views

Introduction to Vectors and NDSolve

I want to use NDSolve for a complicated equation that contains vectors. I am still new to Mathematica, and have really enjoyed what I have learned thus far. Concerning this question, I have already ...
2
votes
2answers
146 views

How to generate pure function solution using NDSolve

Suppose i have an equation NDSolve[{ca'[t]== -0.1*ca[t]*cb[t], cb'[t]== -0.1*2*ca[t]*cb[t], ca[0]== 10, cb[0]== 12},{ca,cb},{t,0,5}] how can i get the ...
2
votes
1answer
198 views

Problem solving a nonlinear differential equation with specific boundary conditions

I am trying to solve the following differential equation: DSolve[{y''[x] == A*B (y[x])^2, y'[0] == -B*C, y'[-D] == 0}, y[x], x] For my system, this ...
1
vote
1answer
89 views

Maximising solutions of NDSolve [duplicate]

I have the following system of differential equations ...
0
votes
0answers
102 views

Boundary value problem: complicated functionals

I am trying to solve a non-linear boundary value problem where the differential equation is a convoluted function of the variable I am trying to solve for. I have attached the code defining the ...
0
votes
0answers
46 views

Troubles with FindFit for ODE (elaboration)

I have asked a question Troubles with FindFit for ODE and get a good-working answer from @belisarius. Nevertheless I need to clarify is it possible to define the same model with ...
3
votes
0answers
160 views

Fractals or other patterns in the quadruple linked pendulum

This will seem like a physics question, but I'm looking for something to do in Mathematica specifically. I've successfully modeled a quadruple linked pendulum by setting up the ODEs and solving them ...
0
votes
0answers
91 views

Plotting Poincare sections for a pendulum

Now before you direct me to this page, I'll start by saying that I'm not really using Hamiltonian mechanics to do this problem. I've already done the Lagrangian and I have solutions for both angles. I ...
2
votes
1answer
98 views

Using NDSolve on a vector-valued PDE

I would like to use NDSolve to evaluate a PDE involving a vector valued function. For instance, I'm looking for something like a heat equation with vector-valued ...
0
votes
1answer
62 views

How can I assign a vector unknown function to solve the ODE system?

I noted that using non-scalar variables is convenient when a system of differential equations is governed by a process that may be difficult to express symbolically. Taking a example from the tutorial ...
1
vote
3answers
128 views

Difficulty understanding Inverse functions are being used by Solve

I am still having difficulty with the differential equation $$\frac{dy}{dt}=y^2-y,\quad y(0)=2$$ Consider: ...
2
votes
1answer
182 views

2 DOF Spring Mass Damper with NDsolve and Equation of Motion in Matrix Form

I'll preface this with the fact that I have no idea what I'm doing. I'm new to Mathematica, I've only used it to solve simple ODEs with NDsolve. I'm trying to solve ...
4
votes
1answer
264 views

How to solve this Integral equation

D[x[t] - x[t - 1]/(2 E), {t, 3}] + Integrate[E^(-δ)*x[t - δ]/5^t, {δ, 2, 2.5}] == 0 I found solve this problem is hard with Mathematica. I also find a article ...
0
votes
1answer
119 views

How to put constraints on NDSolve[] solution

Assumed the following example of double pendulum by Thison (Answered by Jens): Animation of double pendulum Imagine that in the given animation(i.e. http://i.stack.imgur.com/p4TgL.gif ), the second ...