Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles PDF Download
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721832385
Category :
Languages : en
Pages : 36
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Book Description
The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured. Brown, Clifford A. and Bridges, James Glenn Research Center NASA/TM-2006-214364, E-15640, AIAA Paper 2006-2654
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721832385
Category :
Languages : en
Pages : 36
Get Book Here
Book Description
The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured. Brown, Clifford A. and Bridges, James Glenn Research Center NASA/TM-2006-214364, E-15640, AIAA Paper 2006-2654
Author: Clifford A. Brown
Publisher:
ISBN:
Category :
Languages : en
Pages : 14
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Author: Nasa Technical Reports Server (Ntrs)
Publisher: BiblioGov
ISBN: 9781289237646
Category :
Languages : en
Pages : 24
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Book Description
The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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Author: Sanjay Singh
Publisher: Springer Nature
ISBN: 9819713064
Category :
Languages : en
Pages : 605
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Book Description
Author: Suvanjan Bhattacharyya
Publisher: Springer Nature
ISBN: 9811970556
Category : Technology & Engineering
Languages : en
Pages : 479
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Book Description
This book presents the select proceedings of the 48th National Conference on Fluid Mechanics and Fluid Power (FMFP 2021) held at BITS Pilani in December 2021. It covers the topics such as fluid mechanics, measurement techniques in fluid flows, computational fluid dynamics, instability, transition and turbulence, fluid‐structure interaction, multiphase flows, micro- and nanoscale transport, bio-fluid mechanics, aerodynamics, turbomachinery, propulsion and power. The book will be useful for researchers and professionals interested in the broad field of mechanics.
Author: Amy Eileen McCluskey
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Abstract: Research, design, and experimentation were performed in the Gas Dynamics and Turbulence Laboratory at The Ohio State University to control far-field noise for high-speed jets and observe the effects of control with the purpose of noise mitigation. Recently localized arc filament plasma actuators (LAFPA) were developed to force an axisymmetric Mach 0.9 jet. Previous experimentation was improved upon by adding four actuators to an eight actuator equally spaced setup. A new nozzle extension was designed to house these twelve actuators and an adaptor was developed to provide flush mounting of the electrodes of the actuators between the nozzle and extension. The twelve actuators were used to excite the flow over a large frequency range, which was expressed in terms of the non-dimension forcing Strouhal number (StDF). Microphones, mounted at angles of 30° and 90°, were used to collect far-field sound pressure levels. The response of the jet varied greatly with azimuthal mode and StDF. The perturbations were observed to greatly affect the far-field sound pressure levels at StDF's between 0.1 and 5. Furthermore, greater noise mitigation was recorded at higher modes such as azimuthal modes 5 and "6. This was contrasted to the enhanced mixing observed at lower modes such as m = 1 or "1. However, the effects of actuation on the flow were independent of azimuthal mode when forced at a StD higher than about 2. While these patterns and results were observed at an angle of 30° to the jet axis, the effects remained unclear at an angle of 90°. However, the general observation was made that forcing at higher modes significantly reduces far-field noise.
Author: Willard D. Coles
Publisher:
ISBN:
Category : Propulsion systems
Languages : en
Pages : 54
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 732
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Author: American Institute of Aeronautics and Astronautics
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 530
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