A hydrodynamic criterion of alternative bubble departures

Abstract

The bubble departures from two neighbouring brass nozzles (with inner diameter of 1.1 mm) in three liquids: distilled water, mineral and synthetic engine oils were investigated. The numerical simulations were used for reconstruction of liquid flow around the departing bubbles. Bubble movements in liquid have been recorded using a high speed camera. The 2D bubble paths have been reconstructed using: Laplacian of Gaussian filters, algorithm of detection of local extremes of image brightness and Kalman filter. It was shown that during alternative bubble departures bubble paths become repeatable. The dimensionless number (similar to Strouhal number) was proposed to describe oscillating liquid flow generated by departing bubbles over the nozzle outlet. Such number was used for defining the hydrodynamic criterion of alternative bubble departures.

A hydrodynamic interaction between bubbles and gas supply system during gas bubble departures in liquids: an experimental study

“…The influence of the distance between needles on the interaction between bubbles departing from them was investigated in papers 15 , 16 . It was shown that the hydrodynamic interaction can lead to chaotic pressure changes in the gas supply system and consequently chaotic bubble departures 15 .…”

A hydrodynamic interaction between gas bubbles departed in liquid and gas supply system

“…Moreover, the investigations on bubble departure, interactions between bubble-bubble and bubble coalescence are treated as an introduction to investigations on the greenhouse effect caused by escaping methane bubbles in the oceans [3,4]. There are a lot of papers in which the results of experiments of bubble generation from a single [5][6][7][8][9][10][11] and twin or more needles or orifices [12][13][14][15][16][17][18] were described.…”

“…The influence of the distance between needles on the interaction between bubbles that departed from them was investigated in papers [12,13]. It was shown that the hydrodynamic interaction can lead to chaotic pressure changes in the gas supply system and consequently chaotic bubble departures [12].…”

“…The regimes based on synchronisation among orifices and the parameters affecting the bubbling dynamics were described in [14]. In the paper [13] the coefficient of alternative bubble departure from twin needles (ABD) was proposed. It was shown that the interaction between bubbles depends on the distance between needles, air volume flow rate, liquid properties and bubbles departures frequencies.…”

“…In the experiment, bubbles were generated from two glass needles. Based on the results presented in the paper [13] the distance between needles was set as 4 mm and air volume flow rates were set in one of the needles in the range of 0.00492 l/min -0.0424 l/min. For that selected distance between needles and air volume flow rates, the hydrodynamic interaction between bubbles should occur.…”