Understanding of turbulence modulation and particle response in a particle-laden jet from direct numerical simulations

Point-particle direct numerical simulations have been employed to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime with an inlet Reynolds number based on bulk velocity and jet diameter $({D_j})$ of ~10 000. The investigation fo...

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Bibliographic Details
Published in:	Journal of fluid mechanics 2022-11, Vol.950, Article A3
Main Authors:	Zhou, Hua, Hawkes, Evatt R., Lau, Timothy C.W., Chin, Rey, Nathan, Graham J., Wang, Haiou
Format:	Article
Language:	eng
Subjects:	Direct numerical simulation Dissipation Experiments Fluid flow Inertia JFM Papers Kinetic energy Modulation Orbital velocity Particle laden jets Phase velocity Radial velocity Reynolds number Slip velocity Stokes number Transport equations Turbulence Velocity Velocity gradient Velocity gradients
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Summary:	Point-particle direct numerical simulations have been employed to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime with an inlet Reynolds number based on bulk velocity and jet diameter $({D_j})$ of ~10 000. The investigation focuses on three cases with inlet bulk Stokes numbers of 0.3, 1.4 and 11.2. Special care is taken to account for the particle–gas slip velocity and non-uniform particle concentrations at the nozzle outlet, enabling a reasonable prediction of particle velocity and concentration fields. Turbulence modulation is quantified by the variation of the gas-phase turbulent kinetic energy (TKE). The presence of the particle phase is found to damp the gas-phase TKE in the near-field region within $5{D_j}$ from the inlet but subsequently increases the TKE in the intermediate region of (5–20)Dj. An analysis of the gas-phase TKE transport equation reveals that the direct impact of the particle phase is to dissipate TKE via the particle-induced source term. However, the finite inertia of the particle phase affects the gas-phase velocity gradients, which indirectly affects the TKE production and dissipation, leading to the observed TKE attenuation and enhancement. Particle response to the gas-phase flow is quantified. Particles are found to exhibit notably stronger response to the gas-phase axial velocity than to the radial velocity. A new dimensionless figure is presented that collapses both the axial and radial components of the particle response as a function of the local Stokes number based on their respective integral length scales.
ISSN:	0022-1120 1469-7645