Date of Award

5-2012

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical and Aerospace Engineering

Committee Chair(s)

Barton L. Smith

Committee

Barton L. Smith

Committee

Robert E. Spall

Committee

Heng Ban

Abstract

A synthetic jet is formed by periodic oscillation of a fluid through an orifice. The oscillatory motion is driven by diaphragm or other driver. Previous studies have demonstrated that synthetic jet formation and time-averaged cavity pressure are a function of the orifice shape. Traditionally, the performance of the jet is evaluated with varying configurations of fixed driver input voltage or fixed driver displacement. Neither of these measures accurately reflect the efficiency of the actuator. Defining efficiency as "desired output divided by required input," these traditional measures may not account for increase in required driving current or force.

A sharp inside edge of a synthetic jet orifice can result in separated flow and increased momentum flux (due to the decreased flow area) for a fixed driver displacement. This can lead one to believe that efficiency has been improved, when, in reality, much more power was required for the driver. Acoustic power, which is the time-average of volume flow rate through the orifice multiplied by the driving pressure, or in terms of electrical power, it is the driver power times the efficiency of the driver, accurately accounts for the amount of power required to drive the actuator. This study investigates the efficiency of a round (axisymmetric) synthetic jet actuator as a function of the radius of curvature of the interior edge of the orifice. Simultaneous particle image velocimetry (PIV) measurements at the jet exit and cavity pressure measurements are used to measure the acoustic power required to drive the jet. The resultant momentum flux of the jet is used as a measure of output of the jet. Results are obtained for a range of displacement amplitudes (or stroke lengths) and radii of curvature, while Reynolds number is held fixed.

Comments

This work made publicly available electronically on June 10, 2012.

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