TY - JOUR

T1 - Length-scale cascade and spread rate of atomizing planar liquid jets

AU - Zandian, Arash

AU - Sirignano, William A.

AU - Hussain, Fazle

N1 - Publisher Copyright:
© 2019
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.

PY - 2019/4

Y1 - 2019/4

N2 - The primary breakup of a planar liquid jet is explored via direct numerical simulation (DNS) of the incompressible Navier–Stokes equation with level-set and volume-of-fluid interface capturing methods. PDFs of the local radius of curvature and the local cross-flow displacement of the liquid-gas interface are evaluated over wide ranges of the Reynolds number (Re), Weber number (We), density ratio and viscosity ratio. The temporal cascade of liquid-structure length scales and the spread rate of the liquid jet during primary atomization are analyzed. The formation rate of different surface structures, e.g. lobes, ligaments and droplets, are compared for different flow conditions and are explained in terms of the vortex dynamics in each atomization domain that we identified recently. With increasing We, the average radius of curvature of the surface decreases, the number of small droplets increases, and the cascade and the surface area growth occur at faster rates. The spray angle is mainly affected by Re and density ratio, and is larger at higher We, at higher density ratios, and also at lower Re. The change in the spray spread rate versus Re is attributed to the angle of ligaments stretching from the jet core, which increases as Re decreases. Gas viscosity has negligible effect on both the droplet-size distribution and the spray angle. Increasing the wavelength-to-sheet-thickness ratio, however, increases the spray angle and the structure cascade rate, while decreasing the droplet size. The smallest length scale is determined more by surface tension and liquid inertia than by the liquid viscosity, while gas inertia and liquid surface tension are the key parameters in determining the spray angle.

AB - The primary breakup of a planar liquid jet is explored via direct numerical simulation (DNS) of the incompressible Navier–Stokes equation with level-set and volume-of-fluid interface capturing methods. PDFs of the local radius of curvature and the local cross-flow displacement of the liquid-gas interface are evaluated over wide ranges of the Reynolds number (Re), Weber number (We), density ratio and viscosity ratio. The temporal cascade of liquid-structure length scales and the spread rate of the liquid jet during primary atomization are analyzed. The formation rate of different surface structures, e.g. lobes, ligaments and droplets, are compared for different flow conditions and are explained in terms of the vortex dynamics in each atomization domain that we identified recently. With increasing We, the average radius of curvature of the surface decreases, the number of small droplets increases, and the cascade and the surface area growth occur at faster rates. The spray angle is mainly affected by Re and density ratio, and is larger at higher We, at higher density ratios, and also at lower Re. The change in the spray spread rate versus Re is attributed to the angle of ligaments stretching from the jet core, which increases as Re decreases. Gas viscosity has negligible effect on both the droplet-size distribution and the spray angle. Increasing the wavelength-to-sheet-thickness ratio, however, increases the spray angle and the structure cascade rate, while decreasing the droplet size. The smallest length scale is determined more by surface tension and liquid inertia than by the liquid viscosity, while gas inertia and liquid surface tension are the key parameters in determining the spray angle.

KW - Gas/liquid flow

KW - Length-scale distribution

KW - Primary atomization

KW - Spray angle

UR - http://www.scopus.com/inward/record.url?scp=85060304126&partnerID=8YFLogxK

U2 - 10.1016/j.ijmultiphaseflow.2019.01.004

DO - 10.1016/j.ijmultiphaseflow.2019.01.004

M3 - Article

AN - SCOPUS:85060304126

VL - 113

SP - 117

EP - 141

JO - International Journal of Multiphase Flow

JF - International Journal of Multiphase Flow

SN - 0301-9322

ER -