Faculty of Physics - University of Bucharest

UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 2:26

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Conference: Bucharest University Faculty of Physics 2024 Meeting

Section: Physics and Technology of Renewable and Alternative Energy Sources

Title:

3D simulation of particles movement in a gas

Authors:

Catalin HULEA, Sanda VOINEA

Affiliation:

Faculty of Physics, University of Bucharest, Atomistilor 405, Magurele, Romania

E-mail

catalin.alexandru.hulea@gmail.com

Keywords:

3D simulation, molecules, kinetic theory, Van der Waals, Lennard Jones, Morse, Windows

Abstract:

There are many simulations showing the molecules of a gas moving on the screen. It is interesting to see how such a very simple simulation could be written in C++. In this work, starting from the kinetic theory of gases, the first simulation is based on elastic collisions of rigid spheres, where molecules are represented by these spheres. The laws that determine the collisions are discussed in the paper. Some physical parameters are computed during the simulation, such as pressure, temperature and internal energy; the thermal equation of state of the ideal gases is computed and the small error obtained allows us to verify that the simulation is correct. The second simulation is made for Van der Waals gases, where the molecules attract each other at medium range. As a consequence of this attraction, the pressure on the walls is smaller than that of the ideal gases. At microscopic level, the molecular interactions are described by Lennard-Jones potential, which is attractive at medium range, and repulsive at very short range. Also, in this case the Van der Waals equation of state is computed in order to validate the simulation. In both simulations, a histogram with distribution of particles by velocities is displayed; we can see this is the Maxwell distribution, as expected. The user can choose the number of molecules: 100, 1000 or 10000, and the program runs properly on an average contemporary laptop. Three different atomic species can be selected, with their appropriate parameters: oxygen, hydrogen or nitrogen. The last simulation shows how diatomic molecules are formed by atoms interacting via Morse potential. This is a stronger potential than Lennard-Jones, and it only acts at short range, inside the molecules. On the screen, you can see many pairs of atoms, each rotating around their center of mass.