Nonlinear dynamics of self-organising bubble departures from twin nozzles

Abstract

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.