Interaction of a rigid buoyant sphere and a deforming bubble with a vortex ring: The role of deformability

Biswas, Subhajit; Govardhan, Raghuraman N.

doi:10.1103/physrevfluids.7.094302

Cited by 5 publications

(1 citation statement)

References 54 publications

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“…Several physical mechanisms are known to be involved in bubble drag reduction, e.g., the reduction in flow mixture density and reduced viscosity (Legner 1984;Skudarnov and Lin 2006;Elbing et al 2008), bubble deformability lifting the high vorticity regions away from the wall (Van Gils et al 2013;Lu et al 2005), effective compressibility of the flow mixture (Ferrante and Elghobashi 2004), disruption of the coherent flow structures by bubbles (Sugiyama et al 2008;Jha and Govardhan 2015;Biswas and Govardhan 2020, 2022, and the extraction of turbulent energy during bubble deformation and splitting (Meng and Uhlman 1989). These different mechanisms do not exclude each other and are likely to act simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Effects of salt concentration on top wall bubble injection in a turbulent channel flow: bubble dynamics and wall drag reduction

Biswas,

Govardhan

2024

Exp Fluids

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Most applications related to bubble drag reduction (BDR) occur in contaminated environments where the presence of different surface active agents modify bubble coalescence and hence, affect flow drag. Although there have been studies on bubble drag modifications with salt/surfactant, the effects of systematic variation in salt/surfactant concentration on bubble dynamics and drag remain relatively unexplored. Driven by this motivation, in the present work, we experimentally investigate the effects of salt concentration on the bubble dynamics and drag modification in a fully developed horizontal turbulent channel flow for top wall bubble injection, over a wide range of salt concentrations (0< M <0.08, moles/liter), channel Reynolds number (22,500< Re <65,000), and injected bubble void fraction (0< α <0.16). The injected bubbles interact with the flow in the turbulent channel and as they move downstream reach an equilibrium state between the bubbly phase and the fully developed carrier phase that persists further downstream. The equilibrium state of the bubble dynamics is captured by high-speed visualizations and the corresponding drag is obtained from stream-wise pressure drop measurements within the channel. Increasing salt concentration levels is seen to lead to reduction in bubble coalescence and consequently in bubble size that modifies bubble deformability, migration, and distribution near the top wall, with the changes being dependent on the Re and α values. At low Re ≈ 22, 500, the addition of salt leads to a dramatic reduction in bubble sizes (∼ 100 microns)

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