Dynamics of a single cavitation bubble near an oscillating boundary.

Cavitation and its effects are well investigated, especially single bubble cavitation and its collapse near rigid and elastic boundaries. In our current article, we investigated novel experiments of a single cavitation bubble near an oscillatory boundary. We generated the cavitation bubble by laser focusing in water. A flat glass plate was fixed to the shaft of the magnetostriction oscillator coil. We investigated the dynamics of bubbles at two relative wall distances (ratio of the distance between the bubble center and plate surface to the maximum radius of the bubble) of the bubble from the glass plate in combination with four modes of oscillation. Each mode has specific frequency and amplitude of oscillation. The high-speed camera captured the dynamics of the bubble using the back-illumination method with a framing rate of 120Kfps and simultaneously we used an optical CMOS sensor to measure the oscillation of the glass plate. We presented a clear comparison among the bubble dynamics near stationary and oscillating plates with parameters such as oscillating modes and direction. We correlated the dynamics of the bubble with the motion of the plate. In addition, we highlighted the differences including the characteristics of bubble shape and jetting that occurred during the collapse phase. The comparison of the time histories of the bubble's equivalent size postulated that the bubble's collapse times vary significantly in some cases compared to the bubble's dynamics near the stationary plate. In all cases, we noticed the shortening of the bubble's collapsing time, i.e. accelerated collapses. In our findings, we noticed a collapse times reduction of about 4-15%. Our finding signifies the importance of introducing the oscillation of the boundaries to obtain effective energy concentration over the time during the collapse. Our study also suggests that forced oscillation of boundaries is undesirable for destructive cavitation effects. The method we suggested for the manipulation of bubble dynamics holds potential for enhancing the efficiency of applications such as lithotripsy in biomedical devices, actuation and micro pumping in microfluidic devices, and effective semiconductor surface cleaning. Not but least, obtained results can be used as benchmark in future for validating numerical methods.