TY - JOUR

T1 - Study of primary instability of thick liquid films under strong gas shear

AU - Isaenkov, Sergey V.

AU - Cherdantsev, Andrey V.

AU - Vozhakov, Ivan S.

AU - Cherdantsev, Mikhail V.

AU - Arkhipov, Dmitriy G.

AU - Markovich, Dmitriy M.

N1 - Publisher Copyright: © 2018 Elsevier Ltd

PY - 2019/2/1

Y1 - 2019/2/1

N2 - The initial stage of downward co-current annular flow was studied using two optical techniques: brightness-based laser-induced fluorescence technique and shadow technique. The experiments were conducted in a circular pipe and in a rectangular duct. The working area was represented by the first few centimetres from liquid inlet; the latter was organised as a tangential slot. The process of formation of disturbance waves was found to consist of three stages: formation of regular initial two-dimensional high-frequency waves; fragmentation into localised irregular three-dimensional waves and formation of large-scale quasi-two-dimensional disturbance waves. All the stages occur closer to the inlet at higher gas velocities and lower liquid flow rates. It was found that the initial two-dimensional waves appear at the initial area of thick film in the vicinity of the inlet. Spatiotemporal measurements were conducted and spectral and statistical approaches were applied to study the characteristics of the initial waves at the linear growth stage. The obtained characteristics were compared to the linear stability calculations; the comparison showed satisfactory agreement for the frequencies and velocities of the initial waves after taking into account non-equilibrium film thickness at the inlet. (C) 2018 Elsevier Ltd. All rights reserved.

AB - The initial stage of downward co-current annular flow was studied using two optical techniques: brightness-based laser-induced fluorescence technique and shadow technique. The experiments were conducted in a circular pipe and in a rectangular duct. The working area was represented by the first few centimetres from liquid inlet; the latter was organised as a tangential slot. The process of formation of disturbance waves was found to consist of three stages: formation of regular initial two-dimensional high-frequency waves; fragmentation into localised irregular three-dimensional waves and formation of large-scale quasi-two-dimensional disturbance waves. All the stages occur closer to the inlet at higher gas velocities and lower liquid flow rates. It was found that the initial two-dimensional waves appear at the initial area of thick film in the vicinity of the inlet. Spatiotemporal measurements were conducted and spectral and statistical approaches were applied to study the characteristics of the initial waves at the linear growth stage. The obtained characteristics were compared to the linear stability calculations; the comparison showed satisfactory agreement for the frequencies and velocities of the initial waves after taking into account non-equilibrium film thickness at the inlet. (C) 2018 Elsevier Ltd. All rights reserved.

KW - Annular flow

KW - Kelvin–Helmholtz instability

KW - Linear stability theory

KW - Liquid film

KW - Shadow technique

KW - Waves formation

KW - DROPLET ENTRAINMENT

KW - Kelvin-Helmholtz instability

KW - INITIATION

KW - LARGE-EDDY

KW - LASER-INDUCED FLUORESCENCE

KW - LENGTHS

KW - SIMULATION

KW - ANNULAR 2-PHASE FLOW

KW - DISTURBANCE WAVES

UR - http://www.scopus.com/inward/record.url?scp=85057255781&partnerID=8YFLogxK

U2 - 10.1016/j.ijmultiphaseflow.2018.11.010

DO - 10.1016/j.ijmultiphaseflow.2018.11.010

M3 - Article

AN - SCOPUS:85057255781

VL - 111

SP - 62

EP - 81

JO - International Journal of Multiphase Flow

JF - International Journal of Multiphase Flow

SN - 0301-9322

ER -