Flow Regimes in Curved Subsonic Diffusers
01 Sep 1962-Journal of Basic Engineering (American Society of Mechanical Engineers)-Vol. 84, Iss: 3, pp 303-312
About: This article is published in Journal of Basic Engineering.The article was published on 1962-09-01. It has received 120 citations till now. The article focuses on the topics: Flow (mathematics).
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TL;DR: In this article, features of two-dimensional and three-dimensional separating turbulent boundary layer flows are discussed, and the behavior and structure of strong adverse-pressure-gradient separating flows over streamlined surfaces and backward-facing step separations are reviewed.
224 citations
TL;DR: In this article, the authors measured the angular deflection of the glottal jet from the streamwise direction (symmetric configuration) quantified for each realization, with a bimodal flow configuration observed for divergence angles of 10 and 20°, with the flow eventually skewing and attaching to the vocal fold walls.
Abstract: Pulsatile two-dimensional flow through static divergent models of the human vocal folds is investigated. Although the motivation for this study is speech production, the results are generally applicable to a variety of engineering flows involving pulsatile flow through diffusers. Model glottal divergence angles of 10, 20, and 40° represent various geometries encountered in one phonation cycle. Frequency and amplitude of the flow oscillations are scaled with physiological Reynolds and Strouhal numbers typical of human phonation. Glottal velocity trajectories are measured along the anterior–posterior midline by using phase-averaged particle image velocimetry to acquire 1,000 realizations at ten discrete instances in the phonation cycle. The angular deflection of the glottal jet from the streamwise direction (symmetric configuration) is quantified for each realization. A bimodal flow configuration is observed for divergence angles of 10 and 20°, with the flow eventually skewing and attaching to the vocal fold walls. The deflection of the flow toward the vocal fold walls occurs when the forcing function reaches maximum velocity and zero acceleration. For a divergence angle of 40°, the flow never attaches to the vocal fold walls; however, there is increased variability in the glottal jet after the forcing function reaches maximum velocity and zero acceleration. The variation in the jet trajectory as a function of divergence angle is explained by performance maps of diffuser flow regimes. The smaller angle cases are in the unstable transitory stall regime while the 40° divergent case is in the fully developed two-dimensional stall regime. Very small geometric variations in model size and surface finish significantly affect the flow behavior. The bimodal, or flip-flopping, glottal jet behavior is expected to influence the dipole contribution to sound production.
58 citations
Cites background or methods from "Flow Regimes in Curved Subsonic Dif..."
...Fox and Kline (1962) compiled two-dimensional B. D. Erath Æ M. W. Plesniak (&) School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA E-mail: plesniak@ecn.purdue.edu diffuser data, identifying flow regimes based on diffuser parameters....
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...This behavior can be explained by relating the divergence angles of these vocal fold configurations to the diffuser flow regimes for steady inlet flow plotted by Fox and Kline (1962), as shown in Fig....
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...been reported by Iguchi et al. (1990), Ikeda et al. (1994), and Pelorson et al. (1994, 1995, 1996). Teager and Teager (1983) and Kaiser (1983) addressed asymmetric jet behavior in laryngeal flows, including scenarios of complete attachment of the jet to the vocal fold wall....
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...been reported by Iguchi et al. (1990), Ikeda et al. (1994), and Pelorson et al....
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...This can again be explained by the diffuser flow regime map of Fox and Kline (1962). Because N/W1 remains constant, the only variable is W, which increases to 40 ....
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Abstract: Flow through a driven, 7.5 times life-size vocal fold model was investigated at corresponding life-size flow rates of Q
mean
= 89.1 ml/s, 159.4 ml/s, and 253.0 ml/s. The flow was scaled to match physiological values for Reynolds, Strouhal, and Euler numbers. The models were driven at a life-size frequency of 94 Hz. Particle image velocimetry (PIV) data were acquired in the anterior–posterior midplane of the glottis, and the unsteady transglottal pressure drop across the vocal folds was simultaneously measured. Flow and pressure data were obtained at four discrete instances during the closing phases of the phonatory cycle for which t/T
open
= 0.60, 0.70, 0.80, and 0.90. The glottal jet trajectory exhibited a bimodal distribution of flow attachment between the two medial surfaces of the glottis. Vortex shedding at the trailing edge separation point generated instabilities in the shear layer, which caused large oscillations in the glottal jet orientation downstream of the glottal exit. The development of the Coanda effect during the glottal cycle was found to have minimal impact on the transglottal pressure drop, suggesting that flow orientation does not directly influence the dipole sound source. The change in transglottal pressure drop as a result of jet trajectory was less than 2% for all three investigated flow rates.
56 citations
Additional excerpts
...This behavior is not unexpected, as the glottal orientation corresponds to the ‘‘appreciable stall’’ regime, as defined by the performance mappings of diffuser flows by Fox and Kline (1962), and Smith and Kline (1974)....
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TL;DR: In this paper, the authors presented the results of an experimental program with the aim of controlling the flow in a highly unstable 90 deg curved diffuser, which is an integral part of an open jet wind tunnel at the University of Southampton, has the unique configuration of extreme shortness and high area ratio.
Abstract: This paper represents the results of an experimental program with the aim of controlling the flow in a highly unstable 90 deg curved diffuser. The diffuser, which is an integral part of an open jet wind tunnel at the University of Southampton, has the unique configuration of extreme shortness and high area ratio. In this study, several passive flow control devices such as vortex generators, woven wire mesh screens, honeycomb, and guide vanes were employed to control the three-dimensional diffusing flow in a scaled-down model. Although less successful for vortex generators, the other devices were found to improve significantly the uniformity of the flow distribution inside the curved diffuser and hence the exit flow. This study suggests that a cumulative pressure drop coefficient of at least 4.5 at the diffuser exit with at least three guide vanes is required to achieve adequate flow uniformity at the diffuser exit. These flow conditioning treatments were applied to the full-scale diffuser with exit dimensions of 1.3×1.3 m2. Flow with comparable uniformity to the scale-model diffuser is obtained. This study provides valuable guidelines on the design of curved/straight diffusers with nonseparated flow and minimal pressure distortion at the exit.
51 citations
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01 Jan 2003TL;DR: In this article, the basic thermodynamics and fluid mechanics of hydraulic machinery are discussed, as well as the cavitation in hydraulic machinery, including pumps, compressors, fans, axial flow and radial flow.
Abstract: Dimensional analysis - basic thermodynamics and fluid mechanics hydraulic pumps hydraulic turbines centrifugal compressors and fans axial flow compressors and fans steam turbines axial flow and radial flow gas turbine cavitation in hydraulic machinery.
50 citations