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1500 questions
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1 answer

Can I solve this time-independent PDE by adding a time derivative and marching in time?

I want to solve this PDE: Currently I have some code that will automatically generate pde solutions for a very similar pde that includes a time derivative (partial d/ partial t) using an ADI method. I'm wondering if there is a way to approximate…
phubaba
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simple MHD simulation code for (self) education and play with

I would like some super simple computational code for solving magnetohydrodynamics problems. High accuracy nor performance is not my concern. I wan't it just to visually explore qualitative behavior of plasma. Important for me is: Generality - it…
Prokop Hapala
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4 answers

What is an efficient way of notifying MPI processes of receiving messages?

In MPI, is there any built-in mechanism to notify a group of processes that they need to receive messages from other processes? In my application every process needs to send data to a group of processes with known rank IDs (which potentially…
mmirzadeh
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Importance of the Time Step Value for the Accuracy of a Transient CFD Simulation

Overview My understanding is that one should use a time step $\Delta t < \frac{h}{v}$ (where h - smallest mesh element, v - velocity) to get an accurate result. But how important is this really for the accuracy of the simulation? Is it as important…
A.L. Verminburger
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Proper data-structure and algorithm for 3-D Delaunay triangulation

I have worked out some poor code to achieve the goal of 3D Delauney triangulation(random points in E3), but the time consuming is huge, and when five points are exactly (or nearly due to the round-off error) on one sphere, my code can not handle…
mengxia
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Are we free to choose the position of ghost cells on a non-uniform finite-volume mesh?

Following Hundsdorfer approach the finite volume discretisation of the advection-diffusion equation (conservative form) on non-uniform cell centered grid can be written as, $$ w_j^{\prime} = \frac{w_{j-1}}{h_j}\left( \frac{ah_j}{2h_{-}} +…
boyfarrell
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Bounding the relative error of derivative given relative error of the function

Suppose a function $f$ can be computed such that the bound on the relative error is $R$ i.e. $f^-(x) = f(x)(1+r)$ where $f^-$ and $f$ are respectively the computed and exact value $f$ and $|r| \leq R$ I want to bound the relative error of the…
smilingbuddha
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FEniCS CFD work-flow for complex geometries

I have COMSOL and the CFD package therein available, which provides me with an all-in-one solution for solving CFD problems. I have modeled and solved the geometry shown in the pictures below, which took me roughly one hour. Now (just for kicks) I…
seb
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How to recreate this result (from a book)?

The result I'm interested in is found within "Synchronization: A Universal Concept in Nonlinear Sciences" page $333$ figure $14.3$. The peculiar fragment is also provided at the end of this post. So basically there is this dissipative coupling…
Pranasas
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Mesh Independence Study: Is the Independent Mesh Really the Best One?

I am running a mesh independence study. I start with Mesh 1 and proceed up to Mesh 4, each time doubling the number cells in the mesh. In parallel, I am comparing my computational results to experimental data. M. 1 shows poor results. M. 2 shows a…
A.L. Verminburger
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8
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Open-source 3D FEM Solver for Electromagnetics (Time-Harmonic Maxwell)

I was wondering if there exist any good (accurate/fast/easy-to-use) open-source FEM solvers for 3D time-harmonic Maxwell's equations. I am looking to simulate systems a few wavelengths large in the X/Y dimensions and tens of wavelengths in the Z…
Costis
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How to discretize the advection equation using the Crank-Nicolson method?

The advection equation needs to be discretized in order to be used for the Crank-Nicolson method. Can someone show me how to do that?
pandoragami
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Genetic algorithm vs conjugate gradient method

I am trying to optimize some force-field parameters in a molecular framework so that the result of simulation comes as close as it can to the experimental structure. In the past, I have written a genetic algorithm where I essentially randomly sample…
Nick
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Is CFD used in animations / movies / art?

This is not a technical question, and is asked just out of curiosity. Are computational fluid dynamics (CFD) simulations used in animation movies? (something like shallow water equations, explosion problem etc.) In other words, can computational…
Subodh
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Conservative finite-difference expression for the advection equation

Following on from the earlier question I am trying to derive a finite-difference scheme for the advection equation which is conservative. It was suggested that for advection equation with variable velocity, $$ \frac{\partial u}{\partial x} +…
boyfarrell
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