Modelagem matemática e simulação numérica direta de correntes de gravidade poli-dispersas

Abstract

Gravity currents begin when two fluid bodies, with different densities, collides one against other, starting a relative movement in both. This currents are called polydisperses when the excess in density is due to the presence of more than one type of particles, which are characterized by their diameter, diluted in dispersant phase. The purpose of this research is to investigate, using Direct Numerical Simulation (DNS), how different combinations of fine and coarse particles affect the dynamics of the current when two different boundary conditions are imposed on the bottom wall of the domain. There is also interest, using 3D simulation, in investigate how the main tri-dimensional structures influences in its dynamics. Data of an experimental work are used to validate and compare the results for the final deposit profile and front evolution of the current. The suspended mass and complete energy budget are also presented. Two-dimensional simulations showed that the addition of a small amount of fine particles, into a current predominantly composed by coarse particles, affect more significantly the features of the flow than the opposite. Comparisons show us the inability of the two-dimensional simulation to reproduce accurately the intense turbulence generated in 3D, resulting an error in the dissipation term due to convective motion.