Mean velocity distributions in a horizontal air–water flow

Co-current stratified gas–liquid downflow—Influence of the liquid flow field on interfacial structure

“…There is considerable discussion in the literature (e.g. Fabre et al, 1983;Paras and Karabelas (1992) ;Banat, 1992;Wongwises and Kalinitchenko, 2002) that these structures create secondary flows inside the liquid flow field, which are characterized by axial velocity components opposed to the main flow. Axial velocity measurements very close to the gas-liquid interface were not made as they are prone to error; indeed, laser light reflected at the interface acts as a spurious ''reference beam'' reaching the photomultiplier and may cause serious errors (Paras and Karabelas, 1992).…”

“…Paras and Karabelas, 1991;Banat, 1992;Lorencez et al, 1997;Wongwises and Kalinitchenko, 2002). However, studies concerning the flow structure under the wavy gas-liquid interface (i.e.…”

Liquid Layer Characteristics in Stratified Gas-Liquid Downflow: A Study of Transition to Wavy Flow

“…For low gas and liquid flow rates, the liquid layer velocity profile maintains typical laminar flow characteristics. For higher liquid flow rates, where the liquid surface is dominated by 3D small amplitude high-frequency waves, the liquid flow displays typical turbulent characteristics (i.e., the turbulence intensity value, u /u * , has a maximum at y + ∼ 13, and the slope of the PSD in the high frequency range is roughly −5/3, as in the case of turbulent single phase flow [6,9]). However, as the gas flow rate increases, the mean axial velocity, U z , deviates from the von Karman distribution [6,13].…”

“…The flow characteristics, such as liquid hold-up and pressure drop, have been extensively studied in horizontal stratified two-phase flows [7][8][9]. However, studies concerning the flow structure under the wavy interface in thin liquid layers in inclined pipes do not seem to be available in the literature, most likely due to the difficulty in obtaining accurate velocity measurements inside such thin liquid layers.…”

An investigation of channel flow with a smooth air–water interface

“…These trends display a significantly different behaviour with those observed by later researchers. For example, both Paras et al (1998) and Wongwises and Kalinitchenko (2002) measured the air velocity profiles and found that the maximal velocity shifts towards the interface. The inconclusive results of this basic statistical quantity suggest that further study is warranted.…”