• Thotreithem Hongray

      Articles written in Pramana – Journal of Physics

    • Oscillatory dynamics of a charged microbubble under ultrasound

      Thotreithem Hongray B Ashok J Balakrishnan

      More Details Abstract Fulltext PDF

      Nonlinear oscillations of a bubble carrying a constant charge and suspended in a fluid, undergoing periodic forcing due to incident ultrasound are studied. The system exhibits period-doubling route to chaos and the presence of charge has the effect of advancing these bifurcations. The minimum magnitude of the charge 𝑄min above which the bubble’s radial oscillations can occur above a certain velocity 𝑐1 is found to be related by a simple power law to the driving frequency 𝜔 of the acoustic wave. We find the existence of a critical frequency $\omega_{H}$ above which uncharged bubbles necessarily have to oscillate at velocities below $c_{1}$. We further find that this critical frequency crucially depends upon the amplitude $P_{s}$ of the driving acoustic pressure wave. The temperature of the gas within the bubble is calculated. A critical value 𝑃tr of $P_{s}$ equal to the upper transient threshold pressure demarcates two distinct regions of 𝜔 dependence of the maximal radial bubble velocity 𝑣max and maximal internal temperature 𝑇max. Above this pressure, 𝑇max and 𝑣max decrease with increasing 𝜔, while below 𝑃tr, they increase with 𝜔. The dynamical effects of the charge, the driving pressure and frequency of ultrasound on the bubble are discussed.

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