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

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1
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0answers
31 views

Stopping NDSolver at time of error

I am using NDSolver and WhenEvent to solve a system of differential equations. I get this message: ...
0
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0answers
26 views

ParametricNDSolve of differential equation with singularity

I have a differential equation I would like to solve with the ParametricNDSolve. However, the coefficients in the differential equation are singular at a certain value, so sometimes NDSolve crashes ...
2
votes
1answer
73 views

solve nonlinear equations with NDSolve

I am trying to solve a set of equations with NDSolve. one of them is mg*yg''[t] == NN[t] - kb*yg[t]^1 - cb*yg'[t], When the power of yg[t] is 1 the equations could ...
3
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1answer
63 views

How to control when NDSolve is called inside Manipulate

Let's say I have a function which returns the resulting function of a differential equation solved by NDSolve: ...
2
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3answers
55 views

Infinite Expression Error NDSolve

I'm trying to figure out why I am consistently getting an infinite expression error when I'm trying to solve this DE using NDSolve. Any help will be appreciated. ...
0
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1answer
44 views

NDSolve There are fewer dependent variables, {V[S,t]}, than equation

I am trying to solve the BlackScholes PDE for Barrier option. It works fine for european barrier, but errors out on american boundary condition ...
0
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0answers
45 views

PDE with Laplacian time derivative term

Using Mathematica 9 I am trying to solve the 2D PDE: c1*Laplacian[-u[x,y],{z,y}] + c2*D[Laplacian[-u[x,y],{x,y}]] == 0 (Eq.1) with time-dependent Dirichlet ...
0
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1answer
41 views

NDsolve with discontinuous non-numeric PDE coefficients

I want to solve the heat diffusion equation with variable thermal conductivity. So I have the following code ...
0
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0answers
36 views

NDSolve : Solve a single variable-coefficient ODE as series of constant-coefficient ODEs

I have a manipulator equation of the form: $M(q){q''} + C(q,q')q'+G(q) = {0}$ where $M, C$ are $6$ x $6$ matrices, and $G, q$ are $6$ x $1$ vectors and $q$ a function of time. ...
0
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1answer
50 views

Obtain constant from DSolve [on hold]

I need to extract constant C[1] from expression which I get when solve equation. i.e. DSolve[y'[x]==1/(2x),y[x],x] In result Mathematica gives me this one ...
0
votes
1answer
56 views

Evaluate NDSolve within NDSolve

So I am attempting to solve a differential equation which includes a differential equation (i am not sure if this why my code is giving problems). I am pretty sure that everything is as its supposed ...
1
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0answers
35 views

DSolve -> no results

I am trying to solve a system of differential equations. ...
0
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1answer
78 views

How to solve the following fourth order partial differential equation including Laplacian

I wish to solve the following fourth order partial differential equation including Laplacian with the boundary conditions with the initial conditions ...
6
votes
2answers
152 views

Reject diverging solution of NDSolve

I'm trying to numerically simulate a spring system with complex stiffness. In essence systems of the form $x''(t)+ (a+ ib) x(t)=0$ For this simple example an analytic solution is easy to find. The ...
1
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1answer
117 views

How to solve time dependent coupled differential equations using Floquet method?

I have coupled differential equations D[X[t], t] == M[t] X[t] + R[t] where ...
0
votes
2answers
89 views

Problem with NDSolve: derivative interpreted as square [duplicate]

I am using Mathematica 9, and trying to solve a very easy differential equation with NDSolve. The code I have is s=NDSolve[{y'[x]==y[x],y[0]==1},y,{x,0,1}] but I ...
0
votes
0answers
34 views

steady state of coupled partial differential equations

I need to solve coupled differential equations(occur regularly in Phase field theory), \begin{eqnarray} \tau \frac{\partial \varphi}{\partial t} &=& W^2\frac{\partial^2 \varphi}{\partial x^2} ...
2
votes
1answer
78 views

Error accumulation in NDSolve?

I'm trying to solve this system of ODEs numerically: $$\vec{Q} = \vec{P} \times \vec{Q}$$ where vectors $\vec{P}, \vec{Q}$ have 3 components: $$\vec{Q} = \left( Q_1, Q_2, Q_3 \right) $$ $$\vec{P} = ...
2
votes
0answers
75 views

Converting integral equations to differential equations

I am trying to use Mathematica to convert integrals to differential equations, of any order. An example of an integral equation is given below, in Mathematica code. Could you please advise as to the ...
0
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0answers
44 views

How to use NDSolve to solve the system of differential equations? [closed]

Reference: Mathematical model for HIV/AIDS with complacency in a population with declining prevalence from http://downloads.hindawi.com/journals/cmmm/2006/471467.pdf I found the differential ...
5
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0answers
78 views

Compiling FoldList implementation for RK4

Original I'm looking to write an integrator for a function of two variables. Here is my implementation for the RK4 update rule using FoldList. ...
0
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0answers
58 views

NDSolve Syntax Error- 29 simultaneous differential equations [closed]

Please note that I do not need a detailed solution specific to the equations, but rather a general way to fix the error. I am trying to solve 29 simultaneous differential equations in Mathematica ...
-1
votes
0answers
26 views

Plot How to plot dV/d(lnJ) [closed]

I measured I-V characterization, so I've got their data. But sometime I want to plot dV/d(lnJ) curve with my data. Can someone help me? How to plot dV/d(lnJ), J is current density.
0
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1answer
71 views

Solving non-linear ODE analytically in mathematica [closed]

I would like to solve the following differential equations $${dx\over dt}=\beta x-{{(C-x)^2}\over 4k} ,t\in[0, T]$$ where $\beta$,$C$ and $k$ are constant values. Also, the folowing terminal ...
2
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0answers
43 views

ParametricNDSolveValue has a problem with complex numbers

Edited: I have simplified the example compared to before and narrowed the problem down a bit. I would like to use ParametricNDSolveValue as function for data ...
0
votes
0answers
66 views

How do I solve a system of PDE with a Dirichlet boundary condition and piecewise condition Initial?

How do I solve the system of PDE with boundary value like this and initial conditions piecewise Please help me to find a solution in a Wolfram Mathematica program. I have several times ...
3
votes
3answers
134 views

Trouble with differential equation

I tried to solve this differential equation: $$\epsilon y''(x)+xy'(x)=-\epsilon \pi^2 \cos(\pi x)-\pi x\sin(\pi x)$$ with boundary conditions: $y(-1)=-2, \space y(1)=0$. If we take $\epsilon=0.1$, ...
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votes
1answer
99 views
2
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2answers
125 views

Steady State Numerical Solution of Heat Diffusion Equation in 2D

I'v been trying to solve for the steady state of the heat diffusion equation numerically but I cant seem to get it to work. My code is ...
3
votes
1answer
88 views

Use FEM Solver for System of Nonlinear PDEs with Nonlinear Coefficients - Reaction-Diffusion

I am trying to solve a complex transient reaction-diffusion problem numerically in 2D. Let's take a simple system to start, say $$ A+B\rightarrow C \\ C \rightarrow A+B $$ with reaction rate $k_1$ ...
0
votes
0answers
61 views

Retrieving forthcoming step size from NDSolve

I'm solving a system of ODEs with a random component, which changes at each calculation step and depends on the step size. So I'm trying to realize something like this: (1) size of the forthcoming ...
2
votes
3answers
126 views

Why does DSolve return two solutions for my ODE?

I wanted to solve the differential equation: $y’ = (1+2x)\sqrt{y}$ with $y(0) = 1$. It can be done by hand, and to check my answer I typed the following in Mathematica ...
1
vote
4answers
128 views

Why can't Mathematica DSolve my equation? [closed]

I am trying to solve $\begin{cases} v(t) = A \cdot e^{kt} \\ v(t) = s'(t) \\ s(0) = 0 \\ v(0) = A \\ v(6000) = 299792458 \\ s(6000) = 2.37 \cdot 10^{16} \end{cases}$ for $A$ and $k$. But neither of ...
2
votes
0answers
42 views

NDSolve returns asymmetric solution to a symmetric equation

I am trying to find the potential of a conducting cylindrical electrode by solving the Laplace's equation. Both, the boundary conditions and the equation are symmetric w.r.t. the change $r\to-r$. ...
2
votes
1answer
85 views

NDSolve-Problem (Calculating field lines)

I want to calculate the field lines of a quite nasty vectorfield. In general the method works fine - except, one of the components of the VF gets 0 - then NDSolve ...
1
vote
1answer
159 views

Modeling a stellar atmosphere

I'm trying to model a stellar atmosphere using Mathematica. Basically I'm working in a physical and chemical model which combined should give me a profile of the chemical abundance in the atmosphere. ...
4
votes
1answer
60 views

WhenEvent used in a PDE to output independent variable

I want to use WhenEvent with a PDE after it has reached steady state. I'm posting a system of 2 equations (my real system has 6) and I'm solving the advection-diffusion-reaction 2nd order PDE. First ...
3
votes
1answer
91 views

Smoothing a unit step function

I want to smooth a unit step function for use in NDSolve so this function is a smooth function of time (t). How can I do the ...
3
votes
2answers
111 views

Using periodic boundary conditions in NDSolve

I need to solve a 2D linear elliptical equation in polar coordinates using NDSolve, but I can’t seem to get Mathematica to accept the required periodic boundary conditions. My actual differential ...
10
votes
2answers
201 views

How to use NDSolve with discontinuities at internal boundaries?

I don’t know how to impose discontinuous internal boundary conditions (BCs) in NDSolve, so I’ve set up an example problem to illustrate my issue. Consider the simple first-order ODE for $f(z)$ on the ...
11
votes
2answers
248 views

Solve differential equation using a integral form boundary condition

I have a second order differential equation and I want to solve it analytically (DSolve) and numerically (NDSolve) with ...
0
votes
1answer
74 views

How can I check that the general solution obeys the original differential equation?

For example: I solved the following differential equation: y''[x] == (λ x^(3/4) y[x])/Sqrt[1-x] that 0<x<1 with the ...
0
votes
1answer
67 views

How can I use NDSolve with a variable parameter?

I'm a new user and I can't understand how to solve this function for variable values of vr (for example vr from 0 to 5 in steps ...
0
votes
1answer
51 views

Solving differential equation (Analytical or Numerical)

I want to solve the following differential equation for $0 < x < 1$ ...
0
votes
1answer
58 views

NDSolve Problems with Cardiovascular Modeling [duplicate]

I am trying to use 27 simultaneous differential equations to model the cardiovascular system. I have the following code, however, the output isn't giving interpolating functions, but rather another ...
3
votes
3answers
127 views

When using NDsolve, how to determine the positions of steady states?

I am currently trying to numerically solve a set of ordinary differential equations of chemical kinetics. However, I want to implement perturbations only when system reach steady states. For example ...
1
vote
1answer
93 views

Animating a 3D shape along path a (2D and 3D) parametric function curve [Update]

I have a 3D object under the action of gravity field.The trajectory of path is a parabola.I would like to animate , as in the example GIF. ...
0
votes
0answers
37 views

How to get this numerical solution of a integro-differential equation [migrated]

Previously, I ask an NDSolve questions(How to solve the differential equation with Duhamel's integral?), but now a more sophisticated one: ...
4
votes
1answer
144 views
+50

Confirming conservation laws for complex valued functions

Consider the nonlinear Schrödinger equation (I would like to do this for a more complicated set of equations, but to gain understanding I'll consider this simplified case) $$A_t+iA_{xx}+i|A|^2A =0,$$ ...
0
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1answer
32 views

How can one make NDSolve spend less time at irrelevant transient oscillation?

In the solution there is a transient oscillation that is irrelevant. NDSolve spends a lot of time there. Is there a way to optimize it?