EPTT 2022

13th Spring School on Transition and Turbulence

TURBULENCE MODEL FOR DENSE TWO-PHASE FLOW

Submission Author: ricardo catta preta , MG
Co-Authors: ricardo catta preta, Aristeu Silveira Neto, Millena Vale, João Marcelo Vedovotto
Presenter: Aristeu Silveira Neto

doi://10.26678/ABCM.EPTT2022.EPT22-0024

 

Abstract

The phenomenon that we study is related to the concept of turbulence modeling and viscosity in a multiphase flow. We want to convey qualitatively and quantitatively what we understand about the concept of modified viscosity when particles are inserted into a fluid. Beforehand, we need to state some preponderant concepts for the topic investigated. It is necessary to differentiate between viscosity modification and modified viscosity. It is important that before we deal with multiphase flows, we need to define something more fundamental—what is the molecular viscosity of a single-phase flow? As the name suggests, molecular viscosity originates at a level below that perceived by continuum mechanics—that is, at the mesoscale. However, its effects are transmitted and detected at the macroscopic level. As a premise, below any computational grid, the fluid is a continuous medium, and as such, there are friction effects. These effects come from molecular shocks due to relative motion between the fluid molecules. Theses molecular shocks promote fluctuations in the velocity field. The effects of molecular fluctuations on the macroscopic level are not calculated precisely. For a macroscopic analysis, we model as an average behavior the velocity field and thermodynamic variables of the fluid molecules. Thus, the role of molecular viscosity is to represent effects that originate at the mesoscale but are perceived at the macroscopic level. The molecular viscosity makes up the viscous stresses, which represents a force per unit area that opposes fluid flow. We present a mathematical methodology for turbulent flows that transform point particles (2-way formulation) into point densities (3-way formulation). When comparing the turbulent kinetic energy with the result of physical experiment, we noticed a high agreement with the computational results of the proposed modeling.

Keywords

multiphase flow, Multiphase flow modeling, Turbulence Model, bubble induced turbulence

 

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