Perforated Wall Noise in the AEDC-PWT 16-ft and 4-ft Transonic Tunnels PDF Download
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Author: O. P. Credle Publisher: ISBN: Category : Transonic wind tunnels Languages : en Pages : 78
Book Description
The report presents the results of recent studies of noise in Propulsion Wind Tunnel (16T) and Aerodynamic Wind Tunnel (4T). Noise levels in the free stream and at the test section wall were measured in both tunnels as a function of Mach number, Reynolds number, wall angle, and wall porosity. In Tunnel 4T, free-stream noise characteristics were also evaluated with solid (taped) test section walls. Test results revealed that the perforated test section wall holes generate discrete frequency, high energy noise. In Tunnel 16T, there is a critical Mach number range in which a wall hole frequency. Test section noise levels were found to vary slightly with wall angle and significantly with Mach number and wall porosity. The wall porosity corresponding to the minimum noise levels was found in Tunnel 4T. (Author).
Author: O. P. Credle Publisher: ISBN: Category : Transonic wind tunnels Languages : en Pages : 78
Book Description
The report presents the results of recent studies of noise in Propulsion Wind Tunnel (16T) and Aerodynamic Wind Tunnel (4T). Noise levels in the free stream and at the test section wall were measured in both tunnels as a function of Mach number, Reynolds number, wall angle, and wall porosity. In Tunnel 4T, free-stream noise characteristics were also evaluated with solid (taped) test section walls. Test results revealed that the perforated test section wall holes generate discrete frequency, high energy noise. In Tunnel 16T, there is a critical Mach number range in which a wall hole frequency. Test section noise levels were found to vary slightly with wall angle and significantly with Mach number and wall porosity. The wall porosity corresponding to the minimum noise levels was found in Tunnel 4T. (Author).
Author: M. O. Varner Publisher: ISBN: Category : Boundary layer noise Languages : en Pages : 44
Book Description
In an attempt to determine the parameters characterizing the noise environment in transonic tunnels, noise-generating mechanisms for porous-wall tunnels with 60-deg inclined holes were isolated and studied. The noise environment in the test section is separated into three distinct parts: the noise due to jet flow through the porous walls, a wall hole-tunnel resonance phenomena, and the turbulent boundary layer on the test section walls and in the diffuser. Each part is analyzed separately for the effects of aerodynamic and geometric flow constraints on the frequency and power characteristics. The contribution of each of the acoustic models to the test section free-stream fluctuating pressure level is also examined.
Author: R. E. Dix Publisher: ISBN: Category : Aeroacoustics Languages : en Pages : 224
Book Description
Between 1986 and 1990, a large database was compiled at AEDC from the results of a series of wind tunnel experiments investigating the aerodynamics of flow over open cavities. The database, known as the Weapons Internal Carriage and Separation (WICS) database, covered four experiments that were completed in the AEDC wind tunnels. The initial database documentation focused on the test and data, but included very little analysis of the results. The purpose of the present work is to report analysis of the cavity acoustics and trajectory data. In addition, an updated engineering mathematical model for cavity aeroacoustics is presented.
Author: North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development Publisher: ISBN: Category : Aerodynamics Languages : en Pages : 644
Author: N. Sam Dougherty Publisher: ISBN: Category : Aerodynamic noise Languages : en Pages : 108
Book Description
An experimental investigation of acoustic disturbances and means of suppression from ventilated transonic wall samples was performed in a low-background-noise research tunnel at AEDC. Configurations for ventilation investigated were longitudinally slotted walls, with and without baffles in the slots, slats versus round rods, and perforated walls with normal or inclined circular holes with varied hole sizes and varied diameter/wall thickness ratio. Comparative acoustic data were acquired over a broad range of subsonic Mach numbers. Several of these wall configurations were found to emit intense, discrete whistling noise with overall root-mean-square amplitudes as large as five percent of the free-stream dynamic pressure. In all cases except one, suppressed noise levels not exceeding 0.75 percent of the free-stream dynamic pressure were achieved compared to a background noise level for the tunnel of approximately 0.47 percent with solid test section walls. Noise suppression was accomplished by means of appropriate devices added to the wall samples which could have application to actual transonic wind tunnel test sections. (Author).
Author: O. P. Credle
Author: O. P. Credle
Author: M. O. Varner
Author: N. Sam Dougherty (Jr.)
Author: R. E. Dix
Author: T. D. Reed
Author: North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development
Author: 
Author: N. Sam Dougherty
Author: 
Author: United States. National Aeronautics and Space Administration