EPTT 2022

13th Spring School on Transition and Turbulence

Numerical study of the influence of the Schmidt number on bi-disperse particle-laden gravity currents

Submission Author: Guilherme Torres Marques Vidal , RS
Co-Authors: Guilherme Torres Marques Vidal, Jorge Silvestrini
Presenter: Guilherme Torres Marques Vidal

doi://10.26678/ABCM.EPTT2022.EPT22-0082

 

Abstract

Density current, or gravity current, is a phenomenon where one fluid flows through another due to a density difference between them. This kind of flow is formed in many natural situations as well as in situations created by humankind, for example, thunderstorm outflows, pyroclastic flows, sandstorms, and others in the manufacturing process, like sheet glass. Because of that, the study of density currents has applications in many different areas like meteorology, atmospheric pollution, entomology, and the industry of gas and oil. This work focus on the numerical study of bi-disperse particle-laden gravity current in the so-called lock-release configuration. The goal is to understand the effect of the Schmidt (Sc) number on the behavior and dynamics of particle-laden density flows and the formation of their deposits. Simulations using direct numerical simulation (DNS) and implicit large eddy simulation (LES) are performed. Three cases are evaluated for the Schmidt number using the LES approach: (i) unitary value for both particle fractions, (ii) Sc=3 and Sc=1 for coarse and fine particle fractions respectively, (iii) and Sc=9 and Sc=3 for coarse and fine particle fractions. Also, a simulation using the DNS approach for unitary value for both particle fractions of Schmidt number is performed as a reference case. All simulations have a Reynolds (Re) number of 5000. To quantify the study some features of the flow are calculated like the position of the current head, suspended mass, and height of deposit profile. Also, the temporal evolution of the energy budget of the simulations is computed. The results of the simulations are compared with previous physical approach experiments available in the bibliography, getting a good agreement. Analyzing the effect of Schmidt variation in the front head position, show that simulations with double mass diffusivity reach a greater distance than simulations with Schmidt unitary after the flow gets in the deceleration phase and keeps this situation for the rest of the computational time. For suspended mass, it is observed that the fine particles are deposited more quickly by increasing the Schmidt number. Also, it is observed that an increase in the Schmidt number caused a smoothness in the peaks present in the deposit profile. For the temporal evolution of the energy budget, the results show that the principal mechanism for energy dissipation is related to turbulent dissipation, which also increases with the Schmidt number.

Keywords

Bi-disperse current, Particle-laden gravity current, Direct numerical simulation (DNS), Large Eddy Simulation (LES), high-order numerical simulation, Deposition of particles

 

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