PIV Measurement of Internal and External Flow of an Acoustically Levitated Droplet

摘要

The characteristics of the flow structure of an acoustically levitated droplet were experimentally investigated by observing internal and external flow of a drop simultaneously. The flow field has been obtained using Particle Image Velocimetry (PIV). Velocity distributions around a levitated droplet were estimated from PIV results. According to the velocity distributions at the equatorial plane of a levitated water droplet, the flow direction of the internal circulation and the external flow of levitated droplet was opposite, since the circulation in the boundary layer predicted in the early studies was likely-to exist at the interface of droplet. In our previous studies, it has been confirmed the internal motion and external flow have been strongly affected by the viscosity of a liquid. Experimental and theoretical estimation of velocity distributions around a droplet also suggests the mechanism of momentum transport by the theoretically-predicted circulation in the boundary layer.