The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Addition of a chain-cell search method and a Van der Waals force model to a particle dynamics code
Author:	Sweetman, Michael J.
View Online:	njit-etd2003-122 (xii, 121 pages ~ 4.1 MB pdf)
Department:	Department of Mechanical Engineering
Degree:	Master of Science
Program:	Mechanical Engineering
Document Type:	Thesis
Advisory Committee:	Rosato, Anthony D. (Committee chair) Chen, Rong-Yaw (Committee member) Ji, Zhiming (Committee member)
Date:	2003-05
Keywords:	Collision detection mechanism Van der Walls force
Availability:	Unrestricted
Abstract:	This project studies the implementation of a computational time saving technique and adds an additional force model into a discrete element method simulation code. Both aspects of the project are focused on increasing the versatility of an existing particle dynamics code by increasing the execution speed and available force models for simulation. The first portion of the project consisted of adding a function to the collision detection mechanism to hash the particles into a spatial grid. This hashing function allows a search for near neighbor particles to be restricted to the space immediately adjacent to the particle of interest, thereby allowing for significant reductions in the amount of time needed to locate near neighbors. It has been found that the time needed to update the list is reduced to a function of N1.2, from a function of N2, where N is the number of particles in the simulation. The second portion of the project involves the addition of a Van der Waals force model to the simulation code. This force becomes significant when considering small particles, and in some cases it will be even stronger than the gravitational force. The Van der Waals force is found by integrating the contribution from each molecule in a particle to the Van der Waals potential function over the whole particle, thereby obtaining equations that enable the force to be found by treating the particles as a continuum.