Jet Flapping Control with Acoustic Excitation

Shouichiro Iio,Ken Hirashita,Tomomi Uchiyama,Yusuke Katayama,Yoshiaki Haneda,Toshihiko Ikeda

doi:10.4236/jfcmv.2013.12007

Abstract

The dynamics of flapping motion of a rectangular jet under acoustic excitation is studied experimentally by means of hot-wire measurement and flow visualization with smoke method. The excitation sufficiently enables“phase-lock”, which permitted us to extract the organized wave motion from a background field of finite turbulent fluctuations. The mean and fluctuation velocity are investigated and focused on the excitation frequency and the Reynolds number. As the excitation frequency decreases, it was found that the jet flapping and the jet spread were enhanced. The excitation with sub-harmonic frequency has significant effects on the rectangular jet behavior. The maximum value of the periodic velocity fluctuation strongly depends on the excitation frequency.

Highlights

The development of a large coherent structure in a mixing layer of jet flow is responsible for some of the most fascinating aspects of fluid dynamics, such as mixing, transport and instability, etc
A lot of researches have been carried out concerning the mechanism and role of coherent structures in jet flows [3,4,5,6,7,8,9]
Left images are looked into the vortex structures in the near field of the jet, and the visualization images in the far field are showed in right images

Summary

Introduction

The development of a large coherent structure in a mixing layer of jet flow is responsible for some of the most fascinating aspects of fluid dynamics, such as mixing, transport and instability, etc. A lot of researches have been carried out concerning the mechanism and role of coherent structures in jet flows [3,4,5,6,7,8,9]. Ho and Gutmark [12] found that a free jet could be effectively excited by acoustic disturbances in its inherent frequency to obtain more upstream position of a vortex roll-up and more localized, organized and higher energy containing coherent structures. Acoustic excitation in this study is one of a zero net mass flux control method.

Objectives

Findings

Discussion

Conclusion