Effect of Nozzle Outlet Shape on Cavitation Behavior of Submerged High-Pressure Jet

A submerged high-pressure water jet is usually accompanied by severe cavitation phenomenon. An organ pipe nozzle can greatly improve the cavitation performance of the jet, making use of the self-excited oscillation of the flow. In order to study the effect of organ pipe nozzles of different nozzle outlet shapes on cavitation behavior of submerged high-pressure jet, in this paper we build a high-pressure cavitation jet experiment system and carried out a high-speed photography experiment to study cavitation cloud characteristics of a high-pressure submerged jet. Two organ pipe nozzles with and without a whistle were compared. The dynamic characteristics of the cavitation cloud was extracted through the POD method, it was found that the result effectively reflect the dynamic characteristics of the cavitation jet. The reconstruction coefficients of mode-1 obtained by the POD can better reflect the periodic time-frequency characteristics of cavitation development. The effect of the nozzle outlet shape on the cavitation behavior of organ pipe nozzle was analyzed based on unsteady numerical simulation, and it was found that the jet generated by the nozzle with a divergent whistle had a larger vorticity in the shear layer near the outlet. Further, stronger small-scale vortex and much severe cavitation occurred from the nozzle with a divergent whistle.

Experimental Study on the Impingement Characteristics of Self-Excited Oscillation Supercritical CO2 Jets Produced by Organ-Pipe Nozzles

Supercritical carbon dioxide (SCO2) jets are a promising method to assist drilling, enhance oil–gas production, and reduce greenhouse gas emissions. To further improve the drilling efficiency of SCO2 jet-assisted drilling, organ-pipe nozzles were applied to generate a self-excited oscillation SCO2 jet (SEOSJ). The impact pressure oscillation and rock erosion capability of SEOSJs under both supercritical and gaseous CO2 (GCO2) ambient conditions were experimentally investigated. It was found that the impact pressure oscillation characteristics of SEOSJs produced by organ-pipe nozzles are dramatically affected by the oscillation chamber length. The optimum range of the dimensionless chamber length to generate the highest impact pressure peak and the strongest pressure oscillation is within 7–9. The dimensionless pressure peak and the pressure ratio decreases gradually with increasing pressure difference, whereas the pressure oscillation intensity increases with increasing pressure difference and the increasing rate decreases gradually. The dominant frequency was observed to decrease monotonically with increasing chamber length but increases with the increase of pressure difference. Moreover, the comparison of impingement characteristics of SEOSJs under different ambient conditions showed that the values of dimensionless peak impact pressure are similar under the two ambient conditions, and the SEOSJ achieves higher pressure oscillation intensity and dominant frequency in SCO2 at the same pressure difference. The rock breaking ability of the SEOSJ is closely related to its axial impact pressure. The erosion depth and mass loss of sandstone caused by the organ-pipe nozzle with the best impact pressure performance is higher than those produced by other nozzles. The SEOSJ results in a deeper and narrower crater in SCO2 than in GCO2 under the same pressure difference. The reported results provide guidance for SEOSJ applications and the design of an organ-pipe nozzle used for jet-assisted drilling.

Experimental Investigation of Rossiter Modes for an Open Box Cavity With Adjustable Depth

Resonance in aerospace is a phenomenon that engineers have been trying to predict and avoid for a long time. Acoustic resonance is only a part in this field. When it was previously studied, it was mostly in connection with long slender gaps at the fuselage of aircrafts. Lately it has become a focus in the development of highly efficient aero engines. Bleed systems in the compressor part of engines are needed but not easy to place aerodynamically. Additionally, these bleed systems have complex geometries. These geometries coupled with the operational range of modern aircraft from low to high subsonic Mach numbers can create unwanted acoustic resonances. This paper is part of project study of these resonances. Here the bleed geometry is simplified to an open box cavity that is studied experimentally in order to measure its acoustic behavior in low to high subsonic flow. The experimental data is compared to theoretical prediction models to create a baseline for future studies. The results show a good agreement between Rossiter prediction and experiments for a shallow cavity of L/D = 4. Deeper cavities with a length to depth ratio of one and 0.5 represent more organ pipe resonance phenomena. This is especially governed by the geometry of the cavity itself and the height of the test section. All cavities experience a shift in modes depending on the operating point. This mode shift pattern is similar for deeper cavities. However, the operating range can be divided into four sections in which a mode shift occurs for all cavities.

Enhancing cavitation intensity in co-flow water cavitation peening with organ pipe nozzles

Co-flow water cavitating jets induce compressive residual stress through cavitation impacts produced by the collapse of the cavitation cloud. Co-flow water cavitation peening causes minimal surface alteration compared to conventional processes such as shot peening, which is a major advantage. However, enhancement of cavitation intensity for co-flow water cavitation peening nozzles is required for practical applications requiring greater process capability. Scaling of co-flow cavitation peening nozzles to achieve greater cavitation intensity requires higher flow rates, thus requiring pumps of higher capacities. In contrast, organ pipe geometry nozzles can enhance cavitation intensity without significant increase in pump capacity and have been used in deep sea drilling applications. The objective of this work is to study the effects of organ pipe inner jet nozzle geometry on co-flow water cavitation intensity and peening performance relative to a standard (unexcited) inner jet nozzle geometry through experiments on aluminum alloy Al 7075-T651. Nozzle performance is characterized via extended mass loss and strip curvature tests, high-speed visualization of the cavitation cloud, analysis of impulse pressures, and through-thickness residual stress measurements. It is found that the optimum organ pipe inner jet nozzle geometry enhances the mass loss and peak strip curvature by 61% and 66%, respectively, compared to the unexcited inner jet nozzle. Residual stress measurements show that the organ pipe inner jet nozzle produces deeper compressive residual stresses in the material than the unexcited inner jet nozzle.

INFLUENCE OF THE THICKNESS OF THE BACK WALL OF A WOODEN ORGAN PIPE AND THE AIR PRESSURE IN THE WIND CHEST ON ITS SOUND PROPERTIES

The paper presents the results of the study of the influence of the back wall thickness of an organ pipe made of resonant spruce wood and the air pressure in the wind chest on its frequency spectrum. A wooden organ pipe with a replaceable back wall was used in the experiment. The wooden plate used for the back wall had an initial thickness of 7 mm. The plate was gradually thinned in 1 mm decrements to a thickness of 1 mm. For each plate thickness, the frequency spectrum was scanned at four different air pressures, namely 588 Pa, 716 Pa, 814 Pa and 941 Pa. The results of the experiment showed that at a given back wall thickness, the fundamental tone frequency increases with increasing air pressure. The decrease in the back wall thickness was manifested by a decrease in the fundamental frequency. At an air pressure of 716 Pa, the intensity of the fundamental as well as the second harmonic component of the pipe acoustic spectrum increased slightly at all wall thicknesses. With increasing air pressure, the intensity of higher harmonic frequencies also increased. The decrease in the back wall thickness of the wooden organ pipe had only a minimal effect on the intensity of the individual harmonic components of the frequency spectrum. Changing the thickness of the back wall of a wooden organ pipe will not significantly affect its final sound.

Examining Fouquieria splendens in an environmental and ecological context: Effect of topography and interspecific neighbors on ocotillo morphology and distribution

Fouquieria splendens is a stem-succulent native to the Chihuahuan, Mojave, and Sonoran Deserts that spans Mexico and the American Southwest. It is well-known for its variable morphology, the underlying reason for which remains incompletely understood. Here, we attempt to quantify the effect of topographic and interspecific factors on F. splendens morphology and distribution. To this end, we measured 27 ocotillos located in the Organ Pipe Cactus National Monument within the Sonoran Desert during June of 2019. We also quantified the spatial distribution of interspecific neighbors relative to F. splendens within two topographically different sites: a bajada gradient and a plain. Using ocotillo morphology, the distances to the nearest neighbors of ocotillos, and hydrographic data extracted from the National Hydrography Dataset, we demonstrate 1) the effect of major interspecific neighbors, i.e. shrubs and cacti, on ocotillo morphology; 2) the effect of elevation on intraspecific spacing as individuals compete for limited space; and 3) a trade-off between height and number of branches. This places F. splendens morphology in its larger environmental and ecological context, highlighting the importance of individual traits and associated trade-offs among traits affected by topography and interspecific neighbors. By examining the ocotillo in a multi-species community and diverse landscape, this study provides empirical insight into a wider range of factors contributing to the variation in F. splendens morphology and spacing.

The Baroque Clarinet and Chalumeau

The second edition of The Baroque Clarinet (1992) is a history of the clarinet and chalumeau from antiquity to 1760 in six chapters: “Origins of the Chalumeau,” “Music for the Chalumeau,” “The Earliest Clarinets,” “Playing Techniques for the Baroque Clarinet,” “Music for the Baroque Clarinet,” and “Baroque Clarinet in Society.” There are five appendices: four checklists of extant chalumeaux, extant clarinets, chalumeau music and sources from 1694 to 1780, clarinet music and sources from about 1715 to 1760; and a fifth of chalumeau and clarinet concerts, rehearsals, and clarinets for purchase in newspaper advertisements from 1718 to 1760. The second edition has significant additions of makers, players, music, and iconography, that last in a chapter called “The Baroque Clarinet in Society.” Topics discussed include single-reed instruments in Egyptian antiquity and from the 10th through the 17th centuries; the mock trumpet; chalumeaux during the 17th and 18th centuries; Jacob Denner’s chalumeaux and clarinets; an organ pipe that sounds like a chalumeau; chalumeau players; chalumeau descriptions from the mid-18th century; later documented chalumeau makers; chalumeau reproductions; how and why Johann Christoph Denner improved the chalumeau and invented the clarinet, based on previous studies of mechanical inventions; chalumeau and clarinet music and composers; and the Baroque clarinet’s use by traveling musicians, in court and aristocratic music, church and civic music, and military music.

Origins of the Chalumeau

Chapter 1 describes the basic construction of the chalumeau and discusses its ancestors in Egyptian antiquity and from the tenth through the 17th centuries; the mock trumpet; chalumeaux during the 17th and 18th centuries; Jacob Denner’s chalumeaux and clarinets revealed in archival sources and three surviving two-key clarinets; an organ pipe that sounds like a chalumeau; chalumeau players; chalumeau descriptions from the mid-18th century; later documented chalumeau makers; and chalumeau reproductions. Ten surviving chalumeaux are described in detail and biographical information is presented on seven makers. Individual players are identified when playing specific musical works, and the chalumeau size as required in the music. Late-19th- and early-20th-century reproductions of chalumeaux and their makers are identified.

Effects of the exit aspect ratio of organ-pipe nozzle on the axial pressure oscillation characteristics of self-resonating waterjet

Self-resonating waterjet is a kind of high-efficient jet being employed in a number of applications. This study aims to enhance the working performance of self-resonating waterjet by providing organ-pipe nozzles with the optimal exit aspect ratio R o. The characteristics of the axial pressure oscillation of the jets were analyzed with the use of six different R o, which were R o = 2, 2.5, 3, 4, 5, and 6, respectively. The pressure oscillation peak ( Pmax) and amplitude ( P a) were used to evaluate the effects under two inlet pressures of 10 MPa and 20 MPa. Results show that R o has significant influence on the magnitudes of the pressure oscillations and is able to eliminate the self-resonating pulsations. It was found that both Pmax and P a as a function of the standoff distance shows some differences for different R o, while the inlet pressure is almost independent of the trends of Pmax and P a against the standoff distance for all the six R o. Under the experimental conditions, R o = 5 should be the optimal ratio for creating the largest Pmax and P a. While at inlet pressure of 20 MPa, R o = 4 turns to be a preferred value for generating greater values of the P a. It was also found that the relations of the averaged dimensionless Pmax and P a against the dimensionless standoff distance are linear and cubic, respectively. In addition, the dimensionless Pmax against R o is hardly affected by the inlet pressure and standoff distance, while the dimensionless P a as a function of R o is influenced by the standoff distance more than by the inlet pressure.