8
votes
Accepted
Error in Attempting Moving Boundary Fluid System
… why would the system be classified by NDSolveValue a differential-algebric system, since every variable has at least one differential term?
This isn't quite ...
- 52.4k
7
votes
How do I plot the Lorenz attractor inside an ellipsoid?
Unless I've done something wrong, it does not appear that the trajectories stay inside the given ellipsoid. The given ellipsoid can be rewritten as
$$
\frac{P}{b} x^2 + \frac{1}{b} y^2 + \left( z - \...
- 13.6k
6
votes
Solution on nonlinear pde with intial condtion
It produces an error.
You need boundary conditions. You only have initial conditions. For numerical solver, both are needed.
I put some below, but you need to put the correct ones as you know the ...
- 109k
5
votes
Accepted
Symbolic solution for steady-state heat equation i.e. Laplace equation inside cylinder
This post contains several code blocks, you can copy them easily with the help of functions here.
It's not too surprising to see DSolve failing on the problem, ...
- 52.4k
4
votes
Ploting solution to a differential equation with different parameters
Something to get you started,. You can use Manipulate
...
- 109k
3
votes
Accepted
Problem with a DAE and DiscreteVariables (II)
It's well known that DAE solver of NDSolve is generally weaker than its ODE solver. (We should admit DAE solving is generally hard than ODE solving, of course. ) So,...
- 52.4k
3
votes
Solution on nonlinear pde with intial condtion
There are initial values missing.
For an example I assume the following initial values:
U[0, t] == 1.4, V[0, t] == 2
Then there should be a comma instead of a ...
- 24.8k
2
votes
non-linear first ODE with boundary condition
This is the same idea as Nasser's, but my route yielded solutions in a slightly different form.
...
- 216k
2
votes
non-linear first ODE with boundary condition
Here is my hand solution with the help of the computer
Solve
\begin{gather*}
\boxed{\frac{\left(y^{\prime}\right)^{2}}{y^{2}}-\frac{b y^{\prime}}{y}-\frac{k}{3 y^{2}}-\frac{f}{3}=0}
\end{gather*}
With ...
- 109k
2
votes
why DSolve gives "Warning: one or more assumptions evaluated to False." when I am not using any assumptions in the call?
It looks like one of the internal steps of DSolve is running
...
- 21
2
votes
Accepted
Linear ODEs with NDSolve
I have a package for solving eigenvalue boundary value problems using the Compound Matrix Method with the Evans function, which I'll use here. The package is available on my GitHub (which has a ...
- 5,438
2
votes
Heat Equation with Mobile Boundary
Since OP is having difficulty in understanding previous related posts, I'll solve the problem as a favor. But I won't explain much because there's nothing new in this problem compared with previous ...
- 52.4k
2
votes
Problem with a DAE and DiscreteVariables
One can keep differentiating until the DAE turns into an ODE:
...
- 216k
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