Motion and drag of a single bubble in super-purified water

Abstract

We experimentally study the motion and shape of a single rising bubble in super-purified water. We develop an apparatus that is equipped with a measurement system for monitoring both the resistivity and amount of total organic carbon of water in order to evaluate the purity of water. We investigate the critical Reynolds number above which the rising bubble motion changes from rectilinear to zigzag or spiral motion. It is revealed that the critical Reynolds number is susceptible to the range of observation height in the experimental tank. Next, we investigate the effects of the amount of contaminant on bubble motion. The drag coefficient of bubbles in the case of low Reynolds numbers is greatly affected by a small amount of contaminant. We also compare the experimental results of both the terminal rising velocity and drag coefficient with theoretical results for ellipsoidal bubble obtained for high Reynolds number. For smaller bubbles, good agreement is found between the experimental and theoretical results. For larger bubbles, however, discrepancies are prominent. Finally, we examine the effects of the bubble shape on its motion. There exist significant discrepancies between the experimental and theoretical results of aspect ratio as a function of Weber number, even in the range where the experimental and theoretical results in both the terminal velocity and drag coefficient show good agreement.

Energy balance in viscous liquid containing a bubble: Rise due to buoyancy

“…According to the flow transition schemes given by Tripathi et al, the values of Eo and Ga suggest that we are at the beginning of an asymmetric oscillatory region. This observation stays in close agreement with the threshold parameters of path instability given by other researchers with respect to the bubble diameters (> 1.8 cm), aspect ratio (χ > 1.6), and Reynolds number (Re < 600). Significant bubble oscillations in water were reported for We > 3 and χ > 3.7 or for bubbles with diameter > 2.2 mm .…”

Shapes and paths of an air bubble rising in quiescent liquids

“…By varying the viscosity and density of the surrounding medium in our experiments, we could vary the Morton number, M o from 230.314 (for pure Glycerol) to 2.52 × 10 −11 (pure water). In addition, contamination in the tank can also alter the dynamics particularly for smaller bubbles [20][21][22]. However, we have taken care to minimise this problem by changing the liquid frequently, and minimising the time taken to carry out each experiment while allowing sufficient time for the flow to subside after pouring the liquid.…”

Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

“…1 covers a wide range of Ga, underlining the current uncertainty on the path instability threshold. This is partly due to the influence of the setup and to experimental uncertainties in the detection of the incipient instability [15]. However, the key issue is often the presence of surfactants that may affect the gas-liquid interface, changing the shear-free boundary condition satisfied by the liquid into a no-slip one at least on a part of the interface, therefore modifying the flow structure past the bubble, hence the threshold of the instability [16,17].…”