Effect of controlled pulsation on axisymmetric jet behavior.

Abstract

Axisymmetric jets have been observed to investigate the effect of controlled pulsation on the behavior of vortex rings by using the hydrogen bubble technique and hot-film measurement. Pulsed jets had similar velocity profiles in the initial region and in the fully developed region. This similar velocity profile was coincident with that in natural jets. The differences between the two kinds of jets in volume rate, in decay of centerline velocity and in distribution of turbulent intensity, were observed to be remarkable in the initial region. Such differences were caused by the different behavior of vortex rings in the initial region. Behavior of vortex rings in the initial region of pulsed jets was roughly classified into three types by Strouhal number, Sr0 (Sr0 <0.9, 0.9^Sr0 < 2.6, Sr0^2.6). It was found that the pulsation for Sr0 =0.3 was the most dispersive wave in a jet column.

An Experimental Study of Amplitude and Frequency Effects upon a Pulsating Jet

“…11 shows the results can be approximated by the Tollmien's theory at x/d > 1.5 -3.0. According to Seno et al (9) , Tollmien's theory shows a good agreement with their experiment at x/d = 7.0 -11.3. Note that the radial profile at the nozzle exit in Seno et al is almost uniform, and that the profile in the present study is almost subject to the 1/7-power law.…”

“…They showed the existence of a practical upper limit of the jet-pulsation amplitude. Seno et al (9) conducted flow visualisations and velocity measurements at several cases with the combinations of Re, St and the jet pulsation amplitude, and roughly classified the flow into three types by St concerning ring-like vortices near the nozzle exit; namely St < 0.9, St = 0.9 -2.6 and St > 2.6. Petersen & Samet (10) considered the flow instability of a small-amplitude circular pulsating jet at the vicinity of a nozzle exit at Re = 5.6×10 4 .…”

An HMV mapping study of a pulsating jet system

“…This pulsating motion is controlled by the frequency and amplitude of the membrane vibration. An electrode is then mounted above the system and in the presence of a suitable redox active species, can be used to monitor the periodic flow induced by the apparatus Note that the study of oscillating jets has been detailed in the literature and examples of the flow and vortex behaviour of various exit geometries using tracer methods [23] can be found in the literature [24,25]. However, in the system deployed here, the oscillation of flow is bipolar in nature as the liquid is periodically ejected and then drawn back into the body of an apparatus.…”

Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

“…However, for engine applications a more reliable excitation method is required and must be developed. In this context it should be noted that mechanical devices have been successfully employed, for example a reciprocating piston by Binder and Favre-Marinet 14and a rotating disc valve by Seno, et al (15). Fig.…”