Questions tagged [boundary-conditions]

The tag has no usage guidance.

372 questions
Filter by
Sorted by
Tagged with
26 views

NDSolve can't find Neumann Value on domain

Trying to solve for the temperature around an axisymmetric thin disk. Edges of the domain are DirichletConditions which work fine, but the solver can't find the <...
• 131
25 views

Boundary condition error with 2D Poisson equation

I'm trying to solve Poisson's equation for the temperature difference ($\Delta T$) between two layers with known conduction between them. The layers have conductive elements spaced in a hexagonal ...
• 131
66 views

How to Solve a DAE System with Integral Constraint and Moving Boundary in Mathematica?

I am currently working on solving a DAE system in Mathematica, which includes an integral constraint and a moving boundary. I have attempted to use ParametricNDSolve, but it doesn't seem to work for ...
• 103
185 views

Boundary conditions issue with Laplace equation

I'm trying to solve the Laplace equation for two spheres of radius rs raised to a potential of 1 a distance l away from each ...
• 33
46 views

2d diffusion equation with boundary conditions: problem with probability conservation

Version: Mathematica 12 I want to numerically solve the 2d diffusion equation $\partial_t u(x,y,t) = D\Big( \partial_x^2 u(x,y,t)+ \partial_y^2 u(x,y,t) \Big)$ over some region with specific boundary ...
• 101
65 views

Young Laplace equation with shooting method

I am attempting to follow the method outlined in this paper on page 5, where the first step requires solving a 2 point boundary value problem. I have tried using the Shooting Method, but to no avail. ...
72 views

I have a problem with this code because it is time invertible symmetric but it is not working

I have this code I want to check for a numerical solution. I get the same shape. The function $y$ is an invertible in time so I plot $y[x]$ and $p[t]$. The $p$ function should decrease but it isn't ...
• 455
1 vote
116 views

Using numerical method to go backward for ODE [closed]

I want to use this code for the backward Numerical solution but patently not well defined? ...
• 455
88 views

Numerical and analytical solutions do not agree [closed]

Hi everyone could anyone have look why this code is not running? ...
• 455
58 views

Compare Numerical and analytical solution for a simple case!

I wanted to check this equation for analytical and numerical solution but they don't meet each other?? ...
• 455
139 views

• 363
132 views

...
• 41
128 views

Cavity resonator modeling with Wolfram Mathematica

I am attempting to determine eigenfrequencies and the corresponding electric field distribution in a rectangular cavity resonator with perfectly conducting walls. In the simplest case of a rectangular ...
• 41
70 views

How to get the boundary points from ConcaveHullMesh in 3D?

I am trying to visualize the boundary points of a quadratic polynomial that has only real roots where I treat the coefficients as coordinate values. But I am having a problem visualizing them because ...
• 114
75 views

How can I use a loop inside a boundary condition in NDSolveValue?

How can I use the variable i of a "do" loop inside a boundary condition in NDSolveValue, and plot the solution for ...
• 21
1 vote
65 views

Solving BVP using shooting method and plotting the result

I am not able to obtain any plot with the following code. ...
• 41
78 views

...
• 41
78 views

How to set up "mixed" boundary conditions for NDSolve for PDE? [closed]

I have the following PDE that I am able to solve using DirichletCondition with NDSolve as the following: ...
• 125
1 vote
207 views

Unexpected result for Poisson problem on torus (using PeriodicBoundaryCondition)

I want to solve the Laplace problem $-\Delta u=f$ ("analyst's Laplacian") for a given $f$ and unknown $u$ on the torus $[0,2\pi]/\sim$, i.e. a rectangle with opposite sides identified. The ...
• 163
162 views

Partial differential equation with conditions

I am trying to solve this PDE with Mathematica, and I have checked the syntax a lot, but still don't get a solution ...
• 57
76 views

NDSolveValue::ntdvdae and NDSolveValue::icfail while solving system of PDEs

I am trying to solve a system of PDEs, but I get the error NDSolveValue::ntdvdae: Cannot solve to find an explicit formula for the derivatives. NDSolve will try ...
• 6,757
134 views

NDSolve ignores my NeumannValue boundary conditions

I am trying to solve a simple linear differential equation for $f(x,y)$ on a square with area $L\times L =1$. I consider $(\partial_x^2 + \partial_y^2)f + \partial_x \partial_y f = 0$ with the ...
• 123
187 views

Badly conditioned matrix for boundary ODE

I have a coupled boundary ODE with dependent variables $u=u(x)$ and $z=z(x)$, $$u'' - \frac{1}{z} \left( -3 + u'^2 (3 - c\; e^{-g u} z^4) - 6 u' z' \right) = 0\tag{1}$$ z'' + c\; e^{-g u} z^3 (-3 + ...
• 715
1 vote
58 views

First order differential equation with two conditions

I want to produce all possible solutions for this equation: ...
• 153
219 views

Machine overflow when defining boundary conditions

Recently I have been trying to code Maxwell's equations over a closed surface and have been facing some trouble defining the boundary conditions for the magnetic field. The equation for the normal of ...
120 views

Solving Poisson PDE with NDSolve and incomplete BC specifications

When solving the following PDE with a missing BC on the fourth edge ($y=1$): ...
• 14.4k
108 views

NDSolve of a non-linear ODE

I am trying to solve the following non-linear ODE numerically: ...
• 23
1 vote
102 views

R-K fourth order scheme for system of ODEs containing 32 differential equations

In the present code, I am trying to solve the system of differential equations using the R-K fourth-order scheme. I am trying to plot the function u and T, but it is showing some error in the boundary ...
145 views

Iteration show different values in solving a pde in mathematica

I have a pde given below: $u_{t}-u_{xx}+\frac{1}{4}u=0,$ with boundary conditions $u(0,t)=1,\ \ u(1,t)=\frac{1}{2}e^{\frac{-t}{4}}+e^{\frac{-1}{2}},$ where $0\leq x\leq 1$. If the initial iterate is \$...