Novel Nozzle Shapes for Synthetic Jet Actuators Intended to Enhance Jet Momentum Flux

An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was assembled from these two types of nozzles—it had a rounded lip on the inside and straight section on the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were at both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate placed at a small distance downstream of the main nozzle. The actuators with particular nozzles were tested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity profiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were performed at eight power levels and at the actuator resonance frequency. The highest momentum flux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement was approximately 31% in comparison with an effect of the reference nozzle at the same input power. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters for a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated. These values were studied as functions of the dimensionless stroke length.

Separation criteria of nanoscale water droplets from a nozzle plate surface

This paper studies the water nanojet ejection process using molecular dynamics simulation. The results show that nanoscale water droplets cannot separate from the nozzle plate surface when the nozzle aperture has a diameter of 27.5 Å or smaller. The maximum height of the produced water nanojet is reduced after reaching to its highest position when the jet does not separate from the plate surface. Separation phenomenon between the water nanojet and the nozzle plate surface is the most obvious with the 27.5-Å-diameter nozzle aperture for this simulation setup. In addition, initial findings on the characteristics of nanoscale water droplets (width and contact angle) impinging onto a fixed plate surface are revealed in preparation for future investigation.