Abstract
The nonlinear dynamics of self-organising bubble departures from twin nozzles in engine oils was analysed. Air bubbles were generated from twin brass nozzles with an inner diameter equal to 1 mm. The flow of bubbles in bubble chains was recorded using high-speed camera. The time series of air pressure oscillations and signal from laser–phototransistor identifying the presence of bubbles over the nozzles outlet were recorded simultaneously. The self-organising bubble departures were observed and their stability was analysed. It was found that self-organising bubble departures become unstable because of successive (during subsequent bubble departures) decrease of the mean air pressure in one of the nozzle air supply system. It was shown that instability of self-organising bubble departures leads to equalization of pressures in both nozzles air supply systems which causes that simultaneous bubble departures appear. In the present experiment, this process was repeated in a cyclic and chaotic way. It was shown that stable self-organising bubble departures are accompanied by periodic air pressure oscillations in one of the nozzles and chaotic air pressure oscillations in the second one.
Highlights
The self-organising bubble departures were observed in many experimental investigations
The carried out analysis [2, 3] shows that self-organising mechanism of bubble departures depend on hydrodynamic interactions between bubbles
Because the frequency of bubble departures in oils is lower than in water, b Fig. 4 Flow structures of bubbles departed in engine oils for selected air volume flow rates (q = 0.0333 l/min, q = 0.0530 l/ min, q = 0.0769 l/min) and distance between the nozzles. a distance between the nozzles S = 4 mm—mineral oil, b distance between the nozzles S = 8 mm—mineral oil, c distance between the nozzles S = 10 mm—mineral oil, d distance between the nozzles S = 4 mm—synthetic oil, e distance between the nozzles S = 8 mm—synthetic oil, f distance between the nozzles S = 10 mm—synthetic oil the mutual interaction between the flow of bubbles and pressure oscillations in gas supply systems are easier to investigate
Summary
The self-organising bubble departures were observed in many experimental investigations Such experiments were carried out in systems with orifice [1] and nozzles [2, 3]. Alternative bubble departures (self-organising structure of bubble departures), in water from nozzles, were investigated in papers [2, 3] In these experiments, the distance between nozzles was changed from 3 mm up to 10 mm. It has been shown that the appearance of alternative bubble departures depends on the distance between nozzles, their arrangement and the air volume flow rate. The present experiment was carried out with using twin nozzles with independent air supply system in our opinion such experimental stand contraction allows as to observe only the hydrodynamic interactions between departing bubbles.
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