Application of a high-speed laser-induced fluorescence technique for studying the three-dimensional structure of annular gas–liquid flow

Abstract

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.

Solitary waves on falling liquid films in the inertia-dominated regime

“…Fluorescence intensity-based measurements of the instantaneous and local film height have been conducted, for example, in laminar falling films , in annular gas-liquid flows (Alekseenko et al 2009(Alekseenko et al , 2012 and in gas-sheared liquid flows in a horizontal rectangular duct (Cherdantsev, Hann & Azzopardi 2014). Liu and co-workers ) determined the critical Re for the onset of wave formation as a function of the inclination angle, and a phase boundary which separates the saturated, finite-amplitude wave regime from the multipeaked solitary wave regime was identified.…”

“…Liu and co-workers ) determined the critical Re for the onset of wave formation as a function of the inclination angle, and a phase boundary which separates the saturated, finite-amplitude wave regime from the multipeaked solitary wave regime was identified. In the work of Alekseenko et al (2009Alekseenko et al ( , 2012 and Cherdantsev et al (2014), 2D and three-dimensional (3D) film-thickness measurements were used to scrutinise the topology of large-amplitude disturbance waves as a function of Re, and to link the generation of ripples forming atop these waves to the mechanisms of liquid entrainment. Markides and co-workers (Zadrazil, Matar & Markides 2014a; used planar laser-induced fluorescence imaging (PLIF) instead, in order to investigate the coupling between the film-thickness and velocity-field variations over a 2D domain.…”

Three-dimensional investigation of liquid film structure at the initial area of annular-dispersed flow

“…Besides, it would be difficult to completely eliminate optical distortions appearing due to the curvature of the pipe [3]. It was recently shown [4] that the wavy structure of gas-sheared films is qualitatively the same in channels of different shape, size and orientation.…”

“…Reemitted fluorescent light was recorded by high-speed camera and recalculated into local film thickness. Detailed description of this method can be found in [3]. In present experiments, frame rate of high speed camera is 1 KHz; spatial resolution is 0.2 mm/pixel.…”

Experimental characterization of vertical downward two-phase annular flows using Wire-Mesh Sensor

“…Disturbance waves are considered to be crucial interfacial phenomena in annular flows, because they carry a significant fraction of the total liquid flow rate. Alekseenko et al (2012) linked the circumferential non-uniformity to the frequency, amplitude and circumferential size of ripple waves that are formed by the presence of the disturbance waves. The existence of disturbance waves is also important for the entrainment of the liquid phase into the gas core (Azzopardi, 1997).…”