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Numerical Methods
Computing pi with CPUs, GPUs, threads, MPI, Javascript, Arduino, and FPGAs
This year, for “pi day” (March 14th), I figured I’ll post a short article demonstrating how to estimate the value of π using different computer architectures. This topic is somewhat in line with the ASTE-499 Applied Scientific Co...
Numerical Methods
Introduction to Vlasov Solvers
A simple 1D-1V Vlasov code for two-stream instability is developed. The code is based on a splitting scheme proposed by Cheng and Knorr in 1975.
Numerical Methods
Vorticity – Stream Function Formulation for Axisymmetric Flow
Vorticity - Stream Function formulation for incompressible Navier Stokes equation is developed and demonstrated with Python code for flow in a cylindrical cavity. More complex geometry from a Java code is also shown.
Numerical Methods
Brief Intro to GPU PIC with CUDA
This post shows how to develop a PIC plasma simulation code that uses NVIDIA CUDA to perform computations on the graphics card (GPU). Even without any optimization, the GPU version runs almost twice as fast as the CPU version for a large number of pa...
Numerical Methods
Plasma Simulation
Finite Element Particle in Cell (FEM-PIC)
Example Finite Element Particle in Cell code for flow of ions past a charged sphere on an unstructured mesh
Numerical Methods
Plasma Simulation
Particle In Cell Method in Cylindrical Coordinates
Details of implementing plasma simulations with the Particle In Cell Method in cylindrical coordinates. We develop a simulation of a simplistic ion gun.
Numerical Methods
Plasma Simulation
Stretched Mesh
Tutorial on implementing mesh stretching in Particle In Cell codes. Equations for node positions and finite difference coefficients are derived.
Numerical Methods
Flow in a Nozzle
By considering one-dimensional flow, we can derive an expression for the variation of Mach number in a nozzle with a variable area change. Such a relationship is explored here with an interactive demo that allows you to change the shape of a convergi...
Interactive
Numerical Methods
Computing Intersections Between a Cubic Bezier Curve and a Line
Interactive SVG+Javascript code for computing intersections between a line and a cubic Bezier curve.
Interactive
Numerical Methods
Bird’s DSMC0.FOR in Java
G.A. Bird included several example codes with his book on the DSMC method. These codes are written in Fortran 77 which makes them somewhat hard to understand due to short variable names and reliance on global variables. This post is a summary of my e...
Numerical Methods
Efficient Particle Data Structures
Particle codes have very different memory optimization requirements than fluid-based solvers. Here we consider three types of data structures for holding particles that offer an efficient way of adding and removing particles and compare their perform...
Numerical Methods
2D Finite Element Method in MATLAB
This tutorial discusses how to generate unstructured meshes using a Matlab code distmesh.m and how to use the mesh in a Matlab Finite Element Solver to solve the Poisson's equation on an unstructured domain.
Field Solvers
Numerical Methods
Interpolation using an arbitrary quadrilateral
This article describes how to interpolate data between a particle and an arbitrary quadrilateral cell used in non-Cartesian grids. The technique is illustrated with several Matlab / Octave examples. The examples show how pick points located inside th...
Mesh Generation
Numerical Methods
Nonlinear Poisson Solver
Nonlinear Poisson's equation arises in typical plasma simulations which use a fluid approximation to model electron density. This article describes how to solve the non-linear Poisson's equation using the Newton's method and demonstrates the algorith...
Field Solvers
Numerical Methods
Code Optimization: Speed up your code by rearranging data access
Often, a significant code speed up can be accomplished by simply rearranging the way data is stored or accessed in memory. This article compares data access with arrays vs. linked lists, and compares loop ordering for 3D data sets. It also looks at a...
Numerical Methods
Orthogonal Curvilinear Coordinates
Cylindrical and spherical coordinates are just two examples of general orthogonal curvilinear coordinates. In this article we derive the vector operators such as gradient, divergence, Laplacian, and curl for a general orthogonal curvilinear coordinat...
Numerical Methods
Simple Particle In Cell Code in Matlab
This article includes the source code for a simple particle in cell code. The code simulates flow of plasma over a charged plate and is written in Matlab.
Numerical Methods
Plasma Simulation
Multiscale Modeling of Hall Thrusters
One of the topics we specialize in at Particle In Cell Consulting is modeling of electric propulsion (EP) thrusters. These devices generate thrust by accelerating ionized propellant (plasma). One of the most efficient EP devices is the Hall thruster....
Numerical Methods
Get results faster with Java multithreading
Code parallelization is the process of modifying a simulation program so that it can take advantage of multiple computational cores to obtain results faster. One method is to distribute the workload locally in the form of computational threads. Java...
Numerical Methods
The Finite Volume Method
The Finite Volume Method (FVM) is an algorithm for solving differential equations. It is based on the integral formulation of the problem, with each computational element corresponding to a volume over which the integration is performed. It is somewh...
Field Solvers
Numerical Methods