Pulsating jets are very common and useful in various industrial aspects. However, they have some different basic characteristics from steady jets. In this research, the authors reveal both the frequency and the amplitude effects of pulsations on a jet, including large-amplitude cases. Experiments are conducted at a Reynolds number of 5,000, Strouhal numbers of 0.011 -0.27 and velocity-amplitude ratios of 0.1 -1.0. Using a hot-wire anemometry, the authors show centre velocities, radial profiles, half widths and total flow rates at several positions downward a nozzle exit. From centre velocities and radial profiles, we can see that the streamwise scale of the potential core is less than three times the diameter. From half widths and total flow rates, we can see that the pulsation enhances mixing, and confirm the frequency and the amplitude effects specifically. On the other hand, from centre velocities and radial profiles, we cannot see the both effects clearly. As a result, the authors show the combined frequency-and-amplitude effect upon total flow rate, which consists with small-amplitude results by Crow and Champagne (1971), and find the optimum frequencies.
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 ,
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