Yong He

Bio: Yong He is an academic researcher from Nanjing University of Science and Technology. The author has contributed to research in topics: Bubble & Physics. The author has an hindex of 3, co-authored 5 publications receiving 95 citations.

Experimental and Theoretical Studies on the Movements of Two Bubbles in an Acoustic Standing Wave Field

Abstract: When subjected to an ultrasonic standing-wave field, cavitation bubbles smaller than the resonance size migrate to the pressure antinodes. As bubbles approach the antinode, they also move toward each other and either form a cluster or coalesce. In this study, the translational trajectory of two bubbles moving toward each other in an ultrasonic standing wave at 22.4 kHz was observed using an imaging system with a high-speed video camera. This allowed the speed of the approaching bubbles to be measured for much closer distances than those reported in the prior literature. The trajectory of two approaching bubbles was modeled using coupled equations of radial and translational motions, showing similar trends with the experimental results. We also indirectly measured the secondary Bjerknes force by monitoring the acceleration when bubbles are close to each other under different acoustic pressure amplitudes. Bubbles begin to accelerate toward each other as the distance between them gets shorter, and this acceleration increases with increasing acoustic pressure. The current study provides experimental data that validates the theory on the movement of bubbles and forces acting between them in an acoustic field that will be useful in understanding bubble coalescence in an acoustic field.

Experimental and theoretical analysis of detonation products state on bubble dynamics and energy distribution in underwater explosion

Abstract: The initial states and pressure of detonation products in a bubble have a great impact on bubble pulsation in underwater explosions; particularly, the initial accelerated expansion of a bubble can determine the energy distribution. The energy output and distribution of explosives were obtained on the basis of the underwater explosion experiment in this paper. To study the process of bubble pulsation and energy output, we proposed a gas equation of state (EOS) combining the pvk form, Jones–Wilkins–Lee (JWL) EOS, and the initial states of a bubble to take the effects of the initial bubble pressure and detonation products state transformation into account; furthermore, the bubble radius, velocity, and acceleration vs time were obtained through the Rayleigh–Plesset equation under our experimental condition. The differences of bubble behaviors were compared by adopting the JWL EOS and a polytropic EOS with k = 3. The results showed that the initial bubble pressure and detonation products state transformation influence the accelerating expansion and the subsequent bubble oscillation, respectively. Subsequently, comparisons of the energy output and distribution for different gas EOSs showed that the initial shock wave energy for the JWL EOS was underestimated in accelerating expansion, and the bubble energy was overestimated using the polytropic EOS for k = 3; the obtained energy output and distribution had a better agreement with experimental data when adopting the improved gas EOS. In addition, the energy distribution was determined before the detonation products turned to the explosion gas state in initial expansion based on the relationship of the accelerating expansion characteristics and the initial shock wave energy generation. The research has a great significance to reveal the mechanism of bubble pulsation in underwater explosions.

Research on Crude Oil Demulsification Using the Combined Method of Ultrasound and Chemical Demulsifier

Abstract: In this paper, experiments of crude oil demulsification using ultrasound, chemical demulsifier, and the combined method of ultrasound and chemical demulsifier, respectively, at different temperatures (40°C, 60°C, and 70°C) are carried out. The photos of water droplet distribution in crude oil, taken with microscopic imaging system, before and after demulsification using the above methods at 70°C are given. Research results show that the combined method of ultrasound and chemical demulsifier has the best demulsification effect, followed by chemical demulsifier. Ultrasound without using chemical demulsifier has the least demulsification effect. Furthermore, the impact of ultrasonic power, treatment time, and temperature on crude oil demulsification using the combined method of ultrasound and chemical demulsifier is studied. Results indicate that the final dehydration rate increases with the increase of temperatures and ultrasonic power and almost does not change with the increase of ultrasonic treatment time. These important conclusions will provide the foundation for an extensive application of the combined method of ultrasound and chemical demulsifier.