Mithun Ravisankar

• Ravisankar, Mithun; Wang, Dongyue; Atasi, Omer; Legendre, Dominique & Zenit, Roberto (2025). Experimental evidence of a double recirculation within the skirt of a skirt bubble. International Journal of Multiphase Flow. ISSN 0301-9322. 195. doi: 10.1016/j.ijmultiphaseflow.2025.105530. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the dynamics of freely rising bubbles for a range of Eötvös and Morton numbers where a distinct skirt appears. This regime has not been studied in detail through experiments since the late 1970s. Using modern flow visualization techniques, such as high-speed photography and particle image velocimetry (PIV), we gain new insights by analyzing bubble shapes, terminal velocities, and drag forces, and compare our results with recent Direct Numerical Simulations (DNS) of skirt bubble behavior. Our findings confirm the existence of a maximum skirt length, beyond which the skirt becomes unstable. Notably, for the first time in experiments, we provide evidence of a secondary toroidal vortex inside the bubble skirt, observed in a moving frame of reference in agreement with the predictions from DNS.

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