Aerosol dynamics: numerical simulation of thermophoresis and diffusionphoresis phenomena in micro and nano particles in a binary mixture of rarefied gases

Abstract

The thermophoresis and difusiophoresis phenomena, which are responsible by aerosols transport in the atmosphere and in many technologies, will be investigated numerically by considering micro and nanoparticles suspended in a binary mixture of rarefied gases. The phenomena will be modeled numerically via methods of rarefied gas dynamics which are based on either the solution of the Boltzmann equation or in the statistical direct simulation Monte Carlo method. The influence of the gas-surface interaction law, the intermolecular interaction potential and chemical composition of the mixture in the solution of the problem will be analyzed. Evaporation and/or condensation effects on the interface will also be considered. The phoretic forces acting on a rigid and spherical particle will be calculated in a wide range of the Knudsen number, which characterizes the degree of gas rarefaction, and concentration of the mixture. Some values of the Mach number will be considered in order to cover the subsonic, sonic and supersonic regimes. The profile of all the macro-characteristics of the gaseous mixture around the particle, such as pressure, temperature, bulk velocity and heat flux, will be determined in order to analyze the effects of the particle in the equilibrium properties of the gaseous mixture. Parallel computing in GPU (Graphics Processing Unit) will be employed by using the programming architecture CUDA (Compute Unified Device Architecture), developed by NVIDIA. Some experiments will be conducted in cooperation with a researcher from the School of Aeronautics and Astronautics, Purdue University, in order to validate the numerical schemes developed to deal with thermally-driven gaseous mixture flows. Due to the time for execution of the project, the research work will be restricted to mixtures of noble gases so that rotational and vibrational degrees of freedom as well as chemical reactions will be considered further. (AU)