Experimental study on the resonance between the near-wall particle wake and the incoming oscillatory flow

In dispersed multiphase flows at moderate to high particle Reynolds numbers, the wakes generated by particles play a critical role by modifying both the forces on the particles and the surrounding flow field. In various applications, the flow around a particle is typically not stable, but rather contains a range of disturbances. A key fundamental issue concerns how the surrounding disturbance interacts with and modifies such a wake. In this study, an incoming oscillatory flow is generated by the vortex street behind a horizontal cylinder, and the particle wake response to this controlled oscillatory inflow is investigated. A dual-dye visualization method is applied to mark the vortex structures of both the incoming flow and the particle wake. Rhodamine b and fluorescein are used to mark the vortex shedding from the cylinder and the particle wake respectively, enabling clear visualization of interactions between the incoming oscillatory flow and the particle wake. Results show that resonance exists between the particle wake and the incoming oscillation. In addition, natural vortex shedding becomes prominent at higher particle Reynolds number. Large-scale, low-frequency wake motions amplify faster than high-frequency oscillations. This research can provide a preliminary understanding on the particle wake response to different oscillatory inflows.