Na. Vlachos et al., LIQUID-TO-WALL SHEAR-STRESS DISTRIBUTION IN STRATIFIED ATOMIZATION FLOW/, International journal of multiphase flow, 23(5), 1997, pp. 845-863
Experiments were conducted in a horizontal flow loop (24 mm i.d.), usi
ng an electrochemical technique, for measuring liquid-to-wall shear st
ress, at Various positions around the pipe circumference. Measurements
of liquid film thickness, pressure drop as well as visual observation
s were also made. These data complement similar information obtained b
y Paras et al. (1994), in a horizontal 50.8 mm i.d. flow system. Mean
values and other statistical information are obtained from the analysi
s of the shear stress and film thickness data. Visual studies of the g
as/liquid interface confirm that its profile is concave rather than fl
at. The data show that the time-averaged shear stress tends to decreas
e in the lateral direction (i.e. away from the pipe bottom, Theta = 0
degrees) along which the liquid film gradually becomes thinner. Only f
or relatively low superficial gas velocities (e.g. U-G < 15 m/s), the
mean shear stress is almost constant up to Theta = 45 degrees; i.e. in
a flow region where there is a relatively thick liquid layer. An expr
ession is proposed for predicting the shear stress circumferential dis
tribution. By means of momentum balances (utilizing the new data), the
average gas/liquid interfacial friction factor is determined with imp
roved accuracy. Additionally an equivalent gas/liquid interface roughn
ess is expressed in terms of wave characteristics, i.e. wave intermitt
ency and amplitude. (C) 1997 Elsevier Science Ltd.