Turbulent Dispersed Multiphase Flow

Abstract

Turbulent dispersed multiphase flows are common in many engineering and environmental applications. The stochastic nature of both the carrier-phase turbulence and the dispersed-phase distribution makes the problem of turbulent dispersed multiphase flow far more complex than its single-phase counterpart. In this article we first review the current state-of-the-art experimental and computational techniques for turbulent dispersed multiphase flows, their strengths and limitations, and opportunities for the future. The review then focuses on three important aspects of turbulent dispersed multiphase flows: the preferential concentration of particles, droplets, and bubbles; the effect of turbulence on the coupling between the dispersed and carrier phases; and modulation of carrier-phase turbulence due to the presence of particles and bubbles.

Influence of Stokes number on the velocity and concentration distributions in particle-laden jets

“…In summary, the current measurements show that the axial evolution of velocity and concentration decay, as well as jet expansion, of the two-phase jet is lower than similar single-phase jets consistent with current knowledge of particle-laden jets (Balachandar & Eaton 2010). This difference between the current two-phase jet and single-phase jets increases with Stokes number, and is more prominent in the concentration distribution when compared to the velocity distribution.…”

“…This near-field influence can be deduced to augment the already well-known trend, which is also evident here, in which the rates of spread and streamwise decay of a turbulent jet decrease with an increase in Stokes number (Fan et al 1997;Mostafa et al 1989;Hardalupas et al 1989;Prevost et al 1996). The well-known explanation for this is that inertia of the particles relative to the gas-phase increases with Sk 0 (Balachandar & Eaton 2010). Figure 10 presents the centreline velocity decay of the jet for all three Stokes numbers.…”

“…In addition, without detailed inflow profiles of velocity and concentration of both the jet and co-flow, none are suitable for detailed model validation. Indeed, the paucity of two-dimensional experimental data in two-phase turbulent flows has been identified as a major impediment to the advancement of computational fluid dynamic (CFD) models (Balachandar & Eaton 2010;Fairweather & Hurn 2008).…”

Droplets in turbulence: a new perspective

“…Even if φ v is low, a substantial portion of the total kinetic energy can reside in the particle phase if the particles are denser than the carrier fluid. Such particles are inertial and there is a lag in their response to changes in the surrounding flow that leads not only to a net slip in the velocity between the two phases but also to an inertial bias where the particles tend to accumulate in regions of high strain rate or low vorticity in the flow (Balachandar & Eaton 2010). So even if the particles are initially randomly dispersed they can develop clusters at scales larger than the particle size which in turn can have a dynamic effect back on the turbulence.…”

Turbulent thermal convection driven by heated inertial particles

“…Several studies focused on the alteration of turbulent flows by the momentum two-way coupling between phases of particle-laden flows (Boivin, Simonin & Squires 1998;Elghobashi & Truesdell 1993;Ferrante & Elghobashi 2003;Ahmed & Elghobashi 2000;Druzhinin & Elghobashi 2001Eaton 2009). It was found that depending on the mass loading of the particles, their density and diameter, the turbulent kinetic energy of the fluid can be attenuated or enhanced (Tanaka & Eaton 2008;Balachandar & Eaton 2010). Zonta, Marchioli & Soldati (2008) focused on heat transfer in a particle-laden turbulent channel flow with both mechanical and thermal coupling.…”