The charged bubble oscillator: dynamics and thresholds
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Dr. T. Hongray has a Ph.D. in Theoretical Physics from the University of Hyderabad and did his post-doctoral studies at IIIT-B. Prior to joining RV University, he was in Myanmar from 2017 as faculty at Myanmar Institute of Information Technology (MIIT), Mandalay, as part of the Indian team in mentoring and running the academic programs during the initial years of the Institute which was established under the aegis of the Indo-Myanmar Friendship Project.
He is actively involved in research in the areas of complex systems, nonlinear oscillations in neuronal bursting signals, single bubble sonoluminescence (SBSL), bifurcation theories of dynamical systems and computational physics and has published research papers in these fields. He is also very passionate about and actively exploring the area of quantum computation both at a research level and as an accessible course for beginners who want to get into it at the undergraduate level. Besides that, he has an interest in the area of probabilistic robotics, swarm dynamics, and the theory of computer graphics.
Having taught physics, robotics and computer graphics at an undergraduate level and having interacted with students closely, he strongly believes in a teaching approach that encourages healthy collaboration and constant discussions between students and teachers thereby effectively removing the boundary that exist between students and teachers in many traditional educational systems.
Competency begins with having the right mindset.
The nonlinear, forced oscillations of a bubble in a fluid due to an external pressure field are studied theoretically. In the presence of a constant charge on the bubble, the bubble oscillator’s behaviour changes markedly. We report results at significantly higher pressures and forcing frequencies than presented earlier. The influence of the bubble’s ambient radius on thresholds and dynamics is also reported. Charge and pressure thresholds are calculated for the system, delineating different dynamics.
A detailed study is performed on the parameter space of the mechanical system of a driven pendulum with damping and constant torque under feedback control. We report an interesting bow-tie shaped bursting oscillatory behaviour, which is exhibited for small driving frequencies, in a certain parameter regime, which has not been reported earlier in this forced system with dynamic feedback. We show that the bursting oscillations are caused because of a transition of the quiescent state to the spiking state by a saddle-focus bifurcation, and because of another saddle-focus bifurcation, which leads to cessation of spiking, bringing the system back to the quiescent state. The resting period between two successive bursts (T_rest) is estimated analytically.
The effect of charge on the dynamics of a gas bubble undergoing forced oscillations in a liquid due to incidence of an ultrasonic wave is theoretically investigated. The limiting values of the possible charge a bubble may physically carry are obtained. The presence of charge influences the regime in which the bubble's radial oscillations fall. The extremal compressive and expansive dimensions of the bubble are also studied as a function of the amplitude of the driving pressure. It is shown that the limiting value of the bubble charge is dictated both by the minimal value reachable of the bubble radius as well as the amplitude of the driving ultrasonic pressure wave. A non-dimensional ratio ζ is defined that is a comparative measure of the extremal values the bubble can expand or contract to, and we find the existence of an unstable regime for ζ as a function of the driving pressure amplitude, Ps. This unstable regime is gradually suppressed with increasing bubble size. The Blake and the upper transient pressure thresholds for the system are then discussed.
