Self-sustained oscillation of a jet impinging upon a Helmholtz resonator

1987 ◽  
Vol 179 ◽  
pp. 77-103 ◽  
Author(s):  
W. M. Jungowski ◽  
G. Grabitz
Keyword(s):  
Helmholtz Resonator ◽  
Sustained Oscillation ◽  
Flow Oscillation ◽  
Velocity Measurements ◽  
Fluctuating Pressure ◽  
Air Jet ◽  
Oscillation Mechanism ◽  
Large Pressure ◽  
Detached Shock Wave ◽  
Pressure And Velocity Measurements

A planar, sonic, underexpanded air jet induced strong and self-sustained flow oscillation. The jet was bounded by two parallel walls extending between the nozzle and the Helmholtz resonator opposite. This oscillation was characterized by large pressure amplitudes in the resonator and periodic displacement of a detached shock wave. The observed phenomena were in some measure similar to those occurring with Hartmann-Sprenger tubes. Based on the experimental results, including Mach-Zehnder interferograms and fluctuating pressure and velocity measurements, the properties of the oscillation have been described and a model for theoretical analysis has been established. Experimental and numerical investigations have made possible a description of the oscillation mechanism, which is of the relaxation type.

Jet diffusion in the region of flow establishment

1967 ◽  
Vol 27 (2) ◽  
pp. 231-252 ◽  
Author(s):  
Sedat Sami ◽  
Thomas Carmody ◽  
Hunter Rouse
Keyword(s):  
Static Pressure ◽  
Differential Forms ◽  
Turbulent Shear ◽  
Pressure Probe ◽  
Mean Flow ◽  
Fluctuating Pressure ◽  
Air Jet ◽  
Intermittency Factor ◽  
Energy Equations ◽  
Efflux Velocity

In the flow-establishment region of an air jet issuing with an efflux velocity of about 35 ft./sec from a 1.0 ft. diameter nozzle into still air, measurements were made of mean axial and radial velocities, mean static pressure, turbulence intensities, turbulent shear, and pressure fluctuation. For the measurement of the latter a pressure probe using a ceramic piezo-electric tube was developed. Also included in the measurements were the temporal mean gradient and autocorrelation of the axial-velocity fluctuation and the intermittency factor. The fluctuating-pressure and turbulence-intensity fields were observed to be closely similar in form. Through use of the measured distributions of mean-flow and turbulence characteristics, all terms of the integral and differential forms of the momentum and mean-energy equations were evaluated throughout the region. The results are presented herein by curves of variation of each of the terms as they appear in the corresponding equations.

scholarly journals The physiology of oral whistling: a combined radiographic and MRI analysis

2018 ◽  
Vol 124 (1) ◽  
pp. 34-39 ◽  
Author(s):  
Alba Azola ◽  
Jeffrey Palmer ◽  
Rachel Mulheren ◽  
Riccardo Hofer ◽  
Florian Fischmeister ◽  
...  
Keyword(s):  
High Frequency ◽  
Vocal Tract ◽  
Resonant Cavity ◽  
Helmholtz Resonator ◽  
Theoretical Models ◽  
Experimental Models ◽  
Air Jet ◽  
Tongue Position ◽  
Buccal Space ◽  
Opening And Closing

The fluid mechanics of whistling involve the instability of an air jet, resultant vortex rings, and the interaction of these rings with rigid boundaries (see http://www.canal-u.tv/video/cerimes/etude_radiocinematographique_d_un_siffleur_turc_de_kuskoy.13056 and Meyer J. Whistled Languages. Berlin, Germany: Springer, 2015, p. 74–774). Experimental models support the hypothesis that the sound in human whistling is generated by a Helmholtz resonator, suggesting that the oral cavity acts as a resonant chamber bounded by two orifices, posteriorly by raising the tongue to the hard palate, and anteriorly by pursed lips (Henrywood RH, Agarwal A. Phys Fluids 25: 107101, 2013). However, the detailed anatomical changes in the vocal tract and their relation to the frequencies generated have not been described in the literature. In this study, videofluoroscopic and simultaneous audio recordings were made of subjects whistling with the bilabial (i.e., “puckered lip”) technique. One whistling subject was also recorded, using magnetic resonance imaging. As predicted by theory, the frequency of sound generated decreased as the size of the resonant cavity increased; this relationship was preserved throughout various whistling tasks and was consistent across subjects. Changes in the size of the resonant cavity were primarily modulated by tongue position rather than jaw opening and closing. Additionally, when high-frequency notes were produced, lateral chambers formed in the buccal space. These results provide the first dynamic anatomical evidence concerning the acoustic production of human whistling. NEW & NOTEWORTHY We establish a new and much firmer quantitative and physiological footing to current theoretical models on human whistling. We also document a novel lateral airflow mechanism used by both of our participants to produce high-frequency notes.

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