Vortex Shedding in a Dispersed Multiphase Flow

Vortex-induced vibration from cross flow over a cylinder is an important design consideration in devices from flow meters to nuclear reactors. While past researchers have shown that introducing bubbles to the flow decreases vibration amplitude while increasing shedding frequency, the mechanisms causing these changes are not fully understood. Considering individual bubble transport may provide insight, as previous studies demonstrated that the frequency shift depends nonlinearly on bubble size. Using NSF funding, we begin by experimentally and numerically investigating the flow of individual monodispersed bubbles over a cylinder in cross flow, to assess the size-dependent location and time needed for bubbles to be captured in the shed vortices. These statistics are initially predicted using a one-way coupled point-particle tracking model with the flow field computed using high-order LES. The numerical results are then verified experimentally using high-speed camera visualization of a stream of monodisperse bubbles (range of 40-400 microns) introduced upstream of the cylinder. The bubble capture statistics provide insight into the mechanism for frequency shift, which will be explored further in higher phase fraction flows that are no longer one-way coupled.