Influence of Particle Mass Fraction over the Turbulent Behaviour of an Incompressible Particle-Laden Flow

Abstract

The presence of spherical solid particles immersed in an incompressible turbulent flow was numerically investigated from the perspective of the particle mass fraction (PMF or ϕm), a measure of the particle-to-fluid mass ratio. Although a number of different changes have been reported to be obtained by the presence of solid particles in incompressible turbulent flows, the present study reports the findings of varying ϕm in the the turbulent behaviour of the flow, including aspects such as: turbulent statistics, skin-friction coefficient, and the general dynamics of a particle-laden flow. For this purpose, a particle-laden turbulent channel flow transporting solid particles at three different friction Reynolds numbers, namely Reτ=180, 365, and 950, with a fixed particle volume fraction of ϕv=10−3, was employed as conceptual flow model and simulated using large eddy simulations. The value adopted for ϕv allowed the use of a two-way coupling approach between the particles and the flow or carrier phase. Three different values of ϕm were explored in this work ϕm≈1,2.96, and 12.4. Assessment of the effect of ϕm was performed by examining changes of mean velocity profiles, velocity fluctuation profiles, and a number of other relevant turbulence statistics. Our results show that attenuation of turbulence activity of the carrier phase is attained, and that such attenuation increases with ϕm at fixed Reynolds numbers and ϕv. For the smallest Reynolds number case considered, flows carrying particles with higher ϕm exhibited lower energy requirements to sustain constant fluid mass flow rate conditions. By examining the flow velocity field, as well as instantaneous velocity components contours, it is shown that the attenuation acts even on the largest scales of the flow dynamics, and not only at the smaller levels. These findings reinforce the concept of a selective stabilising effect induced by the solid particles, particularly enhanced by high values of ϕm, which could eventually be exploited for improvement of energetic efficiency of piping or equivalent particles transport systems.

Influence of Morphological Parameters on the Flow Development Within Human Airways

“…The simulation setup was configured to maintain a Courant number less than 1, with a time step size equal to 1 × 10 −4 . This consideration ensures that the solution has a stable behavior during the simulation time ( [13,49,53]). Temporal integration was performed by using a backward scheme and the spatial discretisation was solved using second-order interpolation schemes for the gradient and divergence terms.…”

Effect of channel dimensions and Reynolds numbers on the turbulence modulation for particle-laden turbulent channel flows

“…The effect of particle loading on the turbulent structure, viz. streak spacing in turbulent channel flows, has been described by different authors 9,12,13 . Zhou et al 13 observed a non-monotonic behavior of streamwise fluid fluctuations with an increase in mass loading.…”

“…The authors observed very small attenuation even at mass loading of one for the copper particle of St = τ p U cl /δ = 70 where τ p is the particle relaxation time, δ is the halfchannel width, and U cl is the channel centerline velocity. Duque-Daza et al 9 performed the LES of turbulent channel flows for three different Reynolds numbers of Re τ = 180, 365, and 950. For mass loading of 2.96, a complete turbulence collapse was observed at Re τ = 180, while a negligible turbulence modification was observed at Re τ = 950.…”

“…Effect of channel dimensions (ratio of the integral length scale to the particle diameter) and Reynolds number on the turbulence modulation in the limit of high Stokes number and low solid volume loading is scarce in the literature 4,36 . In the case of LES, there are limited studies where turbulence modulation has been explored with the variation of volume fraction/mass loading and Reynolds number 8,9,21 . In this work, we have studied the effect of L/d p and Reynolds numbers on turbulence modulation and found that these are the two important parameters that quantify the attenuation level relative to volume fraction.…”

Assessment of local isotropy, energetics, and modified eddy-viscosity based modelling for particle-laden turbulent channel flows

“…The present analysis of variation of the apparent Kolmogorov constant with particle volume loading and the new methodology will provide insight to develop advanced models for two-phase turbulent flows. This work is important for the current scenario because many studies are performed at similar Reynolds numbers (∼ Re b = 5600) (Armenio, Piomelli & Fiorotto 1999;Kuerten & Vreman 2005;Kuerten 2006;Marchioli, Salvetti & Soldati 2008;Vreman et al 2009;Dritselis & Vlachos 2011;Zamansky, Vinkovic & Gorokhovski 2013;Duque-Daza, Ramirez-Pastran & Lain 2021; which are of practical importance.…”