Interfacial shear stress in wavy stratified gas–liquid flow in horizontal pipes

Experimental flow pattern map, slippage and time–frequency representation of oil–water two-phase flow in horizontal small diameter pipes

“…Additionally, the phase inversion models (Yeh et al, 1964;Decarre and Fabre, 1997) show a better prediction for the transition between the DO/W and DW/O flows. Recently, new progress has been reported by Ullmann and Brauner (2006), Tzotzi and Andritsos (2013), Barral and Angeli (2013), Rodriguez and Castro (2014) in the development of a flow-pattern transition model. Our experimental flow pattern map is expected to provide the data required for evaluating these new models.…”

Statistical characterization of interfacial waves in turbulent stratified gas-liquid pipe flows

“…In laboratory studies, such subdivision has traditionally been based on a combination of visual observation and qualitative spectral analysis (Ayati et al, 2015;Espedal, 1998;Strand, 1993). Meanwhile, mathematical models yielding sub-regime transition criteria have mainly been based on linear stability analysis, see for instance Tzotzi & Andritsos (2013) for a review. Tzotzi & Andritsos (2013) listed the following stratified flow sub-regimes: i) smooth interface, occurring at very low gas and liquid velocities.…”

Experimental Study of the Dynamics of Water Film on an Aluminum Substrate under Wind Shear

“…The films consisted of the underlying water layer occupied by multiple waves. The instability on the films occurred when the viscous dissipation was insufficient to balance the energy transfer to a corresponding neutral wave [33]. Although the variations of the instantaneous film thickness with the wind speed or film flow rate were continuous and smooth, the film flows could be basically separated into two different flow regions: the "3D region" and the "roll-wave region".…”

“…This indicates that the wind speed is the main influence on the interfacial shape. This can be explained by Kelvin-Helmholtz instability theory [33]: when a two layer fluid has differential velocity, the interface will distort due to the momentum transfer. If only flow rate changes and the relative velocity stays the same, the distortion of interfacial shape will be similar, and only the frequency of rolling waves increases to transport the water mass.…”