ACOUSTIC MEASUREMENTS IN SUPERSONIC TRANSITIONAL BOUNDARY LAYERS. PDF Download
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Author:
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ISBN:
Category :
Languages : en
Pages : 35
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Book Description
Surface pressure fluctuations associated with transitional and turbulent boundary-layer flows on a sharp, slender cone at supersonic Mach numbers were experimentally investigated in a 40- by 40-in. supersonic wind tunnel using a flush-mounted 0.25-in.-diam microphone. The results at Mach numbers 3 and 4 demonstrate the feasibility of locating microphones onboard wind tunnel test models to measure overall pressure fluctuations and power spectral distributions in transitional and fully developed turbulent flows. Transition Reynolds numbers determined using a surface microphone are compared with two other established methods of detection. Selected boundary-layer pressure fluctuation characteristics (power spectral density and root-mean-square values) and transition profiles are presented. Methods of data acquisition and analysis are discussed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Surface pressure fluctuations associated with transitional and turbulent boundary-layer flows on a sharp, slender cone at supersonic Mach numbers were experimentally investigated in a 40- by 40-in. supersonic wind tunnel using a flush-mounted 0.25-in.-diam microphone. The results at Mach numbers 3 and 4 demonstrate the feasibility of locating microphones onboard wind tunnel test models to measure overall pressure fluctuations and power spectral distributions in transitional and fully developed turbulent flows. Transition Reynolds numbers determined using a surface microphone are compared with two other established methods of detection. Selected boundary-layer pressure fluctuation characteristics (power spectral density and root-mean-square values) and transition profiles are presented. Methods of data acquisition and analysis are discussed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 35
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Book Description
Surface pressure fluctuations associated with transitional and turbulent boundary-layer flows on a sharp, slender cone at supersonic Mach numbers were experimentally investigated in a 40- by 40-in. supersonic wind tunnel using a flush-mounted 0.25-in.-diam microphone. The results at Mach numbers 3 and 4 demonstrate the feasibility of locating microphones onboard wind tunnel test models to measure overall pressure fluctuations and power spectral distributions in transitional and fully developed turbulent flows. Transition Reynolds numbers determined using a surface microphone are compared with two other established methods of detection. Selected boundary-layer pressure fluctuation characteristics (power spectral density and root-mean-square values) and transition profiles are presented. Methods of data acquisition and analysis are discussed.
Author: Maureen B. Tracy
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 84
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Book Description
Author: E. R. Bergstrom
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Category :
Languages : en
Pages :
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Book Description
Author: Samuel R. Pate
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ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 418
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Book Description
An experimental investigation was conducted to determine the effects of radiated aerodynamic-noise on boundary-layer transition in supersonic-hypersonic wind tunnels. It is conclusively shown that the aerodynamic noise (pressure fluctuations associated with sound waves), which radiate from the tunnel wall, turbulent boundary layer, will dominate the transition process on sharp flat places and sharp slender cones at zero incidence.
Author: P. Balakumar
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ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Book Description
Author: Ira R. Schwartz
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ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 548
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Book Description
Author: William A. Cassels
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ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 76
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Book Description
Boundary-layer transition by the sublimation and impact-pressure techniques and force tests have been performed on three Haack-Adams bodies of revolution of fineness ratios 7, 10, and 13 at zero angle of attack for free-stream Mach numbers of 2.00, 2.75, and 4.63 and a range of Reynolds numbers based on model length of 6 to 15 X 10(to the 6 power) with and without a roughness strip. The grit method of inducing turbulence was found to provide for a nearly complete turbulent flow over the models at the lower Mach numbers and higher Reynolds numbers considered in this study while the amount of trip drag was less than 8 percent of the model drag with transition fixed. A method of interpreting sublimation data was discussed and used and the results compared well with the impact-pressure results.
Author: Lawrence E. Olson
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
Acoustic disturbances and high frequency-low amplitude vibrations have been studied as a means to promote early boundary layer transition in a supersonic stream. A theoretical analysis of the stability characteristics of the leading edge of a blunted delta-wing was used to guide the choice of acoustic and vibration frequencies employed in this experimental study. Air driven acoustic generators, located in the stagnation chamber of the wind tunnel, produced a strong resonant tone at 4.6 KHz, with a sound level above 148 dB. Comparison of the Reynolds number dependent flow field on a delta model at angle of attack, using an oil streak technique for flow visualization, provided an index of the effectiveness of the acoustic disturbances. Operation of the tunnel with the tunnel air supplied through the acoustic generators and with the normal air supply indicated the 'effective' Reynolds number of the wind tunnel was increased by a factor near 1.4 by the acoustic generators. Extensive test section total pressure and flow angularity surveys and force and moment measurements on a winged body showed this increase in effective Reynolds number was produced with no degradation of flow quality. Piezoelectric vibration transducers were mounted in the supporting sting of the delta models, vibrating the models at frequencies ranging from 2.9 KHz to 82 KHz with peak-to-peak amplitudes from 49 microinches to 0.0015 inches. These vibrations were not as efficient as surface roughness of a height comparable to the peak-to-peak vibration amplitude in stimulating boundary layer transition. (Author).
