Within AURIGA’s bubble-scale work package, Djamel Eddine Aissaoui is characterising the lift force on single bubbles in linear shear flow, using Particle Shadow Velocimetry at HZDR.
Single-bubble dynamics are targeted as a key building block for the project’s broader theoretical aim of modelling flow regime transitions in multi-phase fluid dynamics. Accurate closure models for the lift force are central to this effort, since the lateral migration of bubbles governs the local and global void-fraction distribution. While the lift coefficient is well characterised for bubbles rising in pure water, the ionic liquids screened in AURIGA’s experimental phase alter interfacial mobility and, in turn, the sign and magnitude of the lift force. This motivates a dedicated single-bubble lift-force study, following the approach developed by Hessenkemper et al., across a range of aqueous ionic-liquid mixtures, to support the reformulation of the drift-flux model.
The measurement
Single bubbles are released into a vortex-driven bubble column designed to produce a well-defined linear shear flow in the surrounding liquid. Bubble and liquid-phase velocities are measured simultaneously using Particle Shadow Velocimetry (PSV), a direct in-line illumination technique. Bubble trajectories are extracted through automated detection and tracking, and the local lift coefficient is obtained by solving a lateral force balance along each bubble’s path, following Ziegenhein et al. (2018) and Hessenkemper et al. (2020), accounting for the drag, virtual mass and buoyancy forces acting on the bubble. Measurements are conducted in aqueous ionic-liquid (BMIM) solutions at 0.1%, 1%, 5% and 10% mass concentration, allowing the influence of interface contamination on the lift force to be quantified.
The resulting dataset provides the experimental basis needed to reformulate the drift-flux model for interface-contaminated systems, and supports AURIGA’s broader aim of connecting local, bubble-scale properties to the global flow regime transitions studied in the theoretical work package.