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Referring to the discretization of derivatives by Finite differences, and its applications to numerical solutions of partial differential equations.

7 votes

Derivatives Approximation on non uniform grid

So not quite sure what you're missing, but here's how you go about doing this sort of thing. So first, I am assuming this is 1D due to your description. Second, I'm assuming you know the relationship …
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3 votes

Why do I still obtain a unique solution with one-sided formula when b.c. isn't enough?

So the main issue with this is that you are trying to take uniqueness in your approximation, which is based on solving a difference equation, to infer something about your ill-posed PDE problem, like …
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0 votes

Reconstructing fluxes

I am somewhat confused by this question. Why are you evaluating the fluxes at a midpoint of the time step instead of evaluating them at $t = t_{n}$ or $t = t_{n+1}? From what I have seen, fluxes are …
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0 votes

What methods exist to solve for the fluid flow past a cylinder using finite differences on a...

In the past semester, I was busy writing some CFD code for a simulation I needed for an engineering project. I stumbled upon a few methods that can handle complex geometry and still maintain decent si …
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2 votes

Three body problem in C++

So something must be up with your code. I know this because when I just wrote a C++ code to solve this problem with my simulation framework, I got the following result using Explicit Euler: I would …
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1 vote

Solving PDE with state and time dependent boundary conditions

You shouldn't have any problem coding in a conditional boundary condition into the odefun, like the one you defined in your problem statement. Just use the last timestep's value of $u_b$ to do the co …
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3 votes
Accepted

Help implementing finite difference scheme for heat equation

So your first big issue is one you bring up in point (4), where you say you get the error 'u(0, t[m]) = 0 "can't assign to function call"'. You're trying to store data by assigning data to a function. …
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0 votes

implementation of method of line and Runge-Kutta to the given equation

As an example, you should be able to build up a system of equations to solve for the time derivatives if you use something like the following scheme: \begin{align} A \frac{\partial ^2}{\partial x^2}\ …
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3 votes

Calculating the Jacobian for a function containing a derivative

There are some unknowns in what you are doing but for simplicity, suppose we want to find $u(t)$ as discrete times $t_1, t_2, \cdots, t_n$. Let $\textbf{F} = [F(t_1), F(t_2), \cdots, F(t_n)]^T$ and $\ …
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