The average speed distribution for a 30-particle hard disk gas.
The average speed distribution for a 30-particle hard disk gas.
We study ODE event driven models and show how they can be used to detect hard disk collisions in models such as the ideal gas and Newton's cradle. We also introduce discrete maps and Poincare sections.
The Hard Disk Gas Model is a simple inert monatomic gas model that uses ODE events to detect collisions. Particles are initialized with a speed v=1 in random directions and move with constant velocity until a collision event is detected. Conservation of momentum and energy are applied and the simulation is resumed until the next collision event is detected. Although collision detection is not an efficient computation algorithm, it is straightforward, accurate and fast-enough for small numbers of particles.
The following models use ODE events to detect collisions between hard objects (disks or spheres).
Additional models may be be posted for self-study.
The Hard Disk Gas Model was created by Wolfgang Christian using the Easy Java Simulations (EJS) version 4.1 authoring and modeling tool. You can examine and modify a compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open Ejs Model" from the pop-up menu. You must, of course, have EJS installed on your computer.
Information about Ejs is available at: <http://www.um.es/fem/Ejs/> and in the OSP comPADRE collection <http://www.compadre.org/OSP/>.