The wavy structure of liquid film in annular gas-liquid flow was studied using a high-speed modification of the laser-induced fluorescence (LIF) technique, which was adapted for three-dimensional measurements. The three-dimensional structure of different types of waves in regimes with and without liquid entrainment was investigated. A comparison of the circumferential size of different types of waves was performed. Disturbance waves at high liquid Reynolds numbers were shown to be circumferentially non-uniform, and it was shown that this non-uniformity affects the generation of ripples.
Annular gas-liquid flow was investigated using high-speed modification of LIF technique. The evolution of liquid film surface was studied with high spatial and temporal resolution. It was found that all waves may be classified into primary and secondary waves; all the secondary waves arise due to instability of the back fronts of primary waves. The areas of inception and velocity of secondary waves were compared for annular flow with and without entrainment. The similarities and differences of wavy structure in both cases were demonstrated.
Time-averaged shear stress was measured in annular gas-liquid flow. The experiments were conducted in a wide range of phases flow rates, in two pipes of different diameters, with working liquids of different viscosities. The results were compared to a number of empirical correlations. It was shown that for a fixed gas superficial velocity the shear stress shows the same linear dependence on the inlet wetting density for all pipe diameters and liquid viscosities.
The evolution of thin liquid films sheared by a co-current gas flow in a vertical cylindrical channel with an internal diameter of 11.7 mm was studied using a high-speed implementation of the laser-induced fluorescence method. The main purpose of the work was to study the characteristics of the waves during the transition from the gravitational to the shear flow regime. The effect of gas velocity, liquid Reynolds number, and liquid viscosity on wave characteristics has been studied.
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