Noise, Turbulence, and Thrust of Subsonic Freejets from Lobed Nozzles

Zaman, K. B. M. Q.; Wang, F. Y.; Georgiadis, N. J.

doi:10.2514/2.1990

Cited by 46 publications

(9 citation statements)

References 22 publications

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“…Thus, as we move further downstream from nozzle exit ( X/D j = 2.5), the velocity profile become similar to that of jet emanating from the conventional round nozzle. The same trend has already been reported by Zaman et al (2003) in their experimental work on lobed nozzles.…”

Section: Resultssupporting

confidence: 88%

“…As penetration increases the small scale turbulent structures appear well in advance and hence the radial profile of these highly penetrating nozzles deviates largely from conventional nozzle. The same "w" shaped radial profile observed in the present simulations was reported by Zaman et al (2003) for jet emanating from lobed nozzles in their experimental work. As the flow proceeds downstream, the turbulence intensity reduces and as a result the velocity profile gets smoothened to a conventional mode.…”

Section: Comparison Of Mean Axial Velocity For Different Lobe Penetra...supporting

confidence: 90%

“…The predicted sound pressure levels (SPLs) were within 3 dB deviation from the experimental value. An investigation of characteristics of noise, turbulence and thrust of subsonic jet from rectangular lobed nozzle was conducted by Zaman et al (2003). A reduction in noise at low frequency range was reported coupled with an increase in noise in the high frequency range.…”

Section: Introductionmentioning

confidence: 99%

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Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

Paul

Kriparaj

Tide

2020

AEAT

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Purpose The purpose of this study is to investigate the aerodynamic characteristics of subsonic jet emanating from corrugated lobed nozzle. Design/methodology/approach Numerical simulations of subsonic turbulent jets from corrugated lobed nozzles using shear stress transport k-ω turbulence model have been carried out. The analysis was carried out by varying parameters such as lobe length, lobe penetration and lobe count at a Mach number of 0.75. The numerical predictions of axial and radial variation of the mean axial velocity, u′u′ ¯ and v′v′ ¯ have been compared with experimental results of conventional round and chevron nozzles reported in the literature. Findings The centreline velocity at the exit of the corrugated lobed nozzle was found to be lower than the velocity at the outer edges of the nozzle. The predicted potential core length is lesser than the experimental results of the conventional round nozzle and hence the decay in centreline velocity is faster. The centreline velocity increases with the increase in lobe length and becomes more uniform at the exit. The potential core length increases with the increase in lobe count and decreases with the increase in lobe penetration. The turbulent kinetic energy region is narrower with early appearance of a stronger peak for higher lobe penetration. The centreline velocity degrades much faster in the corrugated nozzle than the chevron nozzle and the peak value of Reynolds stress appears in the vicinity of the nozzle exit. Practical implications The corrugated lobed nozzles are used for enhancing mixing without the thrust penalty inducing better acoustic benefits. Originality/value The prominent features of the corrugated lobed nozzle were obtained from the extensive study of variation of flow characteristics for different lobe parameters after making comparison with round and chevron nozzle, which paved the way to the utilization of these nozzles for various applications.

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Section: Resultssupporting

confidence: 88%

Section: Comparison Of Mean Axial Velocity For Different Lobe Penetra...supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

Paul

Kriparaj

Tide

2020

AEAT

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“…When a conventional splitter mixer is replaced by a lobed mixer, mixing efficiency of the mixed flow is found to be raised apparently [2]. Moreover, both the infrared signal and the aero-acoustic noise are suggested to be alleviated with the usage of a well-designed lobed mixer [3] [4]. However, due to the enhanced mixing process downstream of the lobed trailing edge, more energy losses are required for the mixing process.…”

Section: Introductionmentioning

confidence: 99%

Influence of Core Swirling Motion on Aerodynamic Performances of Lobed Exhaust Nozzle

Ding¹,

Liu²,

Du³

2019

Preprint

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Influence of core flow inlet swirl angle on aerodynamic performances of an exhaust nozzle with scarfed lobed mixer was studied by the validated computational approach. The computational simulation was conducted by resolving the steady form of discretized three-dimensional Reynolds Averaged Navier-Stokes equations with the shear stress transport k-Ω turbulence model. Simulation results depict that swirling motions have ignorable influence on the flow field of the top part in the cross sections slightly downstream of the lobed trailing edge. Besides, for the flow field downstream of the L/D=0.1 cross section, the swirling motions are suggested to cause the clockwise stream-wise vortex to stretch into several smaller-scale vortexes. When the case with a bigger swirling angle is investigated, the induced smaller-scale vortexes are more strengthened by the swirling motions. Concerning the 15° swirling case, the loss caused by the destroyed vortex pattern and the benefit induced by the improved smaller-scale vortexes almost counteract with each other with respect to the thermal mixing efficiency. In the last studied cross section as compared with the baseline case, the case with a maximum swirling angle of 30° has increased 6.94% for the thermal mixing efficiency and decreased 0.42% for the total pressure recovery coefficient.

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“…Schematic of a generic lobed mixerThe enhancement in mixing in the presence of lobes is primarily attributed to the increase in interfacial area and the formation of coherent streamwise vortices[106,107].Paterson[108] performed the first detailed study of the lobed-mixer flow field and revealed the existence of the streamwise vortices that develop from radially oriented secondary flows prevailing along the sidewalls of the lobes. Werle et al[109] and Eckerle et al[110] observed the streamwise vortices to have a diameter on the order of the lobe width upon formation.…”

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confidence: 99%

Computations and Measurements of the Effects of Trailing-Edge Geometry on the Wake of Bluff Bodies

Caylan¹

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This study has aimed to shed further light on the wake dynamics of a bluff body with a streamlined fore body and a rectangular blunt base through experiments and numerical analysis. Specifically, the study was designed to establish the role of instability modes and small-scale turbulence in shaping the wake dynamics, and the effect of boat tails including lobed geometries on the wake structure. In the absence of small-scale turbulence, the near wake of the body is dominated by the effects of two instability modes that promote larger-scale transient motions. Small-scale turbulence is found to have a significant suppressing effect on these motions. Presence of a straight tail is observed not to alter the fundamental structure of the wake, but the relative roles of the instability modes affecting the wake and the resultant streamwise mixing rates are modified. The straight tail is noted to reduce the initial size of the wake significantly to yield substantial reduction in form drag. Shaping the tail into a lobed trailing edge is found to modify the initial cross-section of the wake to an extent to negate the drag-reduction benefits produced by the tail in the straight configuration. Furthermore, the lobed configuration introduces three-dimensional coherent vortical structures at the tail trailing edge that dominate the near-wake development as well as promoting cross-stream mixing farther downstream. iii First and foremost, I would like to thank my thesis supervisor, Dr. Metin I. Yaras, for his instruction, patience, advice, and encouragement. His intelligence and enthusiasm have undoubtedly shaped me for the better, into what I am today. I also wish to gratefully acknowledge Dr. Brian R. McAuliffe of the National Research Council of Canada (NRC) for his collaboration in the work. Further, I would like to thank my close friend and colleague in our research group, Chanon Pretorius. Chanon and I started the journey of our masters at the same time and learnt a lot from each other over the course of our graduate years. It has been a blast working with him. I am grateful to my fellow students and colleagues for not only their assistance, but also their friendship; these include (names are in alphabetical order) Adnan

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Noise, Turbulence, and Thrust of Subsonic Freejets from Lobed Nozzles

Cited by 46 publications

References 22 publications

Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

Influence of Core Swirling Motion on Aerodynamic Performances of Lobed Exhaust Nozzle

Computations and Measurements of the Effects of Trailing-Edge Geometry on the Wake of Bluff Bodies

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