An Experimental Study of Amplitude and Frequency Effects upon a Pulsating Jet(Fluids Engineering)

Abstract

Pulsating jets are very commoll and useful in varieus industriul aspects ． However ， し hey have some difFerent basi ¢ characteristics from steady jets ， h1 亡 his res 已arch ， the authors reveal both the frequency and the a 皿 plitude effects of puLsations 〔 ＞ n a let ， including large − amplitude cases ． Experi・ ments 且 re conducted at a Reynolds number of 5000 ， Stronhal numbers of (， ． Dll − O ． 27 and velocity − amplitude ratios of e ． 1 − 1 ． O． Using a hot − wire anemometry ， the authors show centre velocities ， radial pr面 les， half width5 and total now rates at several positions downward a rユ ozzle exit ． From centre velocities and radial profiles， we can see that the streamwise g ． cale of the potential core is less than three t〒 mes the diameter ． From half widths and total flow rates ， we can see that the pulsation enhances mix 正 ng ， and col 甫 rm the frequency and the aniplitude effects specifically ． On the other hand ， from centre veloci し ies and radial profiles， we can not see the both effects clearly ． As a result ， the au 亡 hors show the coln1 ， ined frequency − amplitude effect on total flow rute ， whi じ h consists with small ． amplitude vesults by Crow and Champagne ｛ ／ 97⊥) ， and find the optimum frequencies ，