Bubble motion in moderate Re crossflow over a cylinder

Vortex shedding in bluff-body flows appears in offshore structures and heat exchangers. Previous studies have shown that with the introduction of bubbles into the carrier liquid, the shedding frequency increases monotonically with respect to void fraction up to a gas volume fraction, α, of 10%. To gain insight on how bubbles interact with the shedding flow, we start with nominally one-way coupled experiments at α<0.01%, and will later expand to α=O(1%). For our low void fraction experiments, a single highly monodisperse stream of bubbles is injected upstream of a 25 mm circular cylinder in crossflows with Reynolds number up to 25,000. The bubble diameter is varied between experiments, as bubble size has been observed to modify the shedding frequency at higher void fractions. High-speed cameras are used to track 3D bubble trajectories, and simultaneous Stereo PIV and dynamic pressure transducer measurements are used to relate the bubble trajectories to the shedding phase and flow field.