Imaging of the self-excited oscillation of flow past a cavity during generation of a flow tone

Abstract

Flow through a pipeline-cavity system can give rise to pronounced ff ow tones, even when the inflow boundary layer is fully turbulent. Such tones arise from the coupling between the inherent instability of the shear flow past the cavity and a resonant acoustic mode of the system. A technique of high-image-density particle image velocimetry is employed in conjunction with a special test section, which allows effective laser illumination and digital acquisition of patterns of particle images. This approach leads to patterns of velocity, vorticity, streamline topology and hydrodynamic contributions to the acoustic power integral. Comparison of global, instantaneous images with time-and phaseaveraged representations provides insight into the small-scale and large-scale concentrations of vorticity, and their consequences on the topological features of Streamline patterns, as well as the streamwise and transverse projections of the hydrodynamic contribution to the acoustic power integral. Furthermore, these global approaches allow the definition of effective wavelengths and phase speeds of the vortical structures, which can lead to guidance for physical models of the dimensionless frequency of oscillation.

Generation of tones due to flow past a deep cavity: Effect of streamwise length

“…These configurations include jet excitation of a long (closed) organ pipe (Cremer and Ising, 1967;Fletcher, 1974Fletcher, , 1976Fletcher, , 1979, jet-sequential orifice plates (Howe, 1975(Howe, , 1980Flatau and Van Moorhem, 1990;Hourigan et al, 1990), wake from a plate in a test section (Parker, 1966;Cumpsty and Whitehead, 1971;Stoneman et al, 1988), shear layer-cavity resonator (DeMetz and Farabee, 1977;Elder, 1978;Nelson et al, 1981Nelson et al, , 1983, and cavity shear layer-long pipeline (Pfizenmaier, 1973;Schachenmann and Rockwell, 1980;Schachenmann, 1982a, 1982b;Karadogan, 1982, 1983;Davies, 1981Davies, , 1996aDavies, , 1996bRockwell et al, 2003;Geveci et al, 2003;Oshkai et al, 2004). The configuration of a cavity shear layer-side branch (deep cavity) is not addressed in the foregoing.…”

The research of the structure and flow characteristics of water- and abrasive-water fan jet

“…Dla wykonywania analiz wyników przeprowadzanych badań, posługiwano się aparatem matematycznym opracowanym i zaadaptowanym na potrzeby oprogramowania Koncerto2 [9]. Dokonując analiz uzyskanych obrazów, moż-na określić średnie czasowe przebiegi kierunkowych skła-dowych prędkości strugi w układzie ortogonalnym, według poniższych zależności:…”

“…[8][9].340 SEIJI SHIMIZU GUOYI PENG YASUYUKI OGUMA * W referacie zaprezentowano istotne aspekty badań struktury i charakterystyki przepływu płaskiej strugi wodnej i wodno-ściernej wytwarzanej w dyszy szczelinowej. Badania takie przeprowadzane w Nihon University w Japonii, metodą prześwietlania takiej strugi suspensyjnej przy uży-ciu techniki laserowej (PIV), pozwalają na wyodrębnienie zachowań poszczególnych jej składników w strefie erozji oraz określenie rozkładów prędkości cząstek materiału ściernego.…”

Aeroacoustic power generated by multiple compact axisymmetric cavities: Effect of hydrodynamic interference on the sound production

“…A single cavity in a pipe line with an acoustic feedback due to a longitudinal standing wave has been the focus of a considerable number of experimental studies, [7][8][9][10][11][12][13] in which the effect of various geometric parameters such as the depth of the cavity and the width of the cavity is addressed.…”