Trajectory Analysis of Rising Spheroidal Bubbles in a Rolling Column

Abstract

The rise of spheroidal bubbles is emulated using a hexapod with periodic angular perturbations to mimic bubble paths in columns onboard seagoing vessels. Bubble trajectories are determined using high-speed camera imaging/ultrasound Doppler velocimetry in vertical, inclined, and rolling columns. The performances of the measurement techniques are compared based on the bubble rise velocity time series and frequency spectra. A hierarchy of reference frames is developed to relate the bubble velocity/acceleration components in the (non-)Galilean frames and to infer from trajectography the lift and drag forces applying to the bubble in the moving-bubble frame. Wall disruption during bubble flights in the rolling column is scrutinized using various geometric/dynamic metrics to underline the dissimilarities between near-wall and centerline bubble path oscillations. Although Coriolis, centrifugal, and Euler accelerations play roles neither on the bubble streamwise rise nor the bubble accelerations, the time-varying character of the buoyancy force brings in dynamic features to the bubble rise in a rolling column that are distinct from those observed in static inclined columns.