Flight Measurement of Wall-pressure Fluctuations and Boundary-layer Turbulence PDF Download

Author: Harold R. Mull
Publisher:
ISBN:
Category : Pressure
Languages : en
Pages : 30

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Author: John S. Serafini
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 88

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This experimental study was carried out at a free-stream Mach number of 0.6 and a Reynolds number per foot of 3.45 x 106. The magnitudes of the wall-pressure fluctuations agree with the Lilley-Hodgson theoretical results. Space-time correlations of the wall-pressure fluctuations generally agree with Willmarth's results for longitudinal separation distances. The convection velocity of the fluctuations is found to increase with increasing separation distances, and its significance is explained. Measurements with the longitudinal component of the velocity fluctuations indicate that the contributions to the wall-pressure fluctuations are from two regions, an inner region near the wall and an outer region linked with the intermittency.

Author: Creighton Lane
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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The turbulent boundary layer (TBL) noise generated inside an aircraft can have a detrimental impact on humans. In an effort to better understand TBL physics and measurement techniques, measurements of the fluctuating wall-pressure beneath a TBL have been performed in an anechoic wind tunnel. The measurements were made using an array of pressure microphones provided by Bombardier Aerospace. Analysis of frequency spectra indicated several shortcomings of the array, namely a low saturation limit and electrical issues, however the low speed spectra agree well with the Goody prediction model. Furthermore, an investigation of the relationship between wall-pressure and velocity fluctuations was performed using a pinhole mounted microphone and simultaneous hot-wire boundary layer measurements. This revealed flow interference from the hot-wire apparatus, obscuring the expected relationships and trends. Several areas of improvement have been identified, including higher saturation limit microphones, LDA for velocity measurements, and increasing rigidity of the experimental setup.

Author: John S. Serafini
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 63

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Pressure fluctuations of a turbulent layer along a plane boundary were investigated. All measurements were made at a nominal free-stream Mach number of 0.6 and an average Reynolds number per foot of 3.45 x 10 to the 6th power in a wind-tunnel facility specially designed for the purpose. The pressure fluctuations were measured with miniature pressure transducers and the velocity fluctuations with hot-wire anemometers. The rootmean-square magnitudes of the wall-pressure fluctuations agree with the Lilley-Hodgson theoretical results, whereas the mean-square spectra do not agree, except over a small range of frequencies. Measurements of the correlations of the wall-pressure fluctuations with the longitudinal component of the velocity fluctuations indicate that the contributions to the wall-pressure fluctuations are from two regions, an inner region near the wall and an outer region linked with the intermittency. (Author).

Author: Chi-Sheng Yang
Publisher:
ISBN:
Category : Turbulence
Languages : en
Pages : 101

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Measurements of the turbulent pressure field on the outer surface of a 3 inch diameter cylinder were made at a point 24 feet downstream of the origin of the turbulent boundary layer. The root-mean square wall pressure was 2.42 times the wall shear stress. The normalized power spectrum at high frequencies contained twice the energy density of the spectrum beneath a plane boundary layer. The convection speed was the same as that in a plane boundary layer but the eddy size was smaller by a factor of two. The smaller eddy size and unchanged convection speed account for the greater energy in the spectrum at high frequencies. (Author).

Author: C. E. Wooldridge
Publisher:
ISBN:
Category :
Languages : en
Pages : 108

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 538

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Author: Alan. L. Kistler
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ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 62

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Author:
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ISBN:
Category :
Languages : en
Pages : 78

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This study is an investigation into the suitability of various wavevector-frequency models of turbulent boundary layer wall pressure fluctuations for the prediction of experimental measurements of turbulent boundary layer wall pressure spectra. Three separate models of the wavevector- frequency spectrum proposed by D.M. Chase in 1980 and 1987 are evaluated. The wavevector-frequency spectral models are integrated numerically using a formulation for the point wall pressure spectrum (based on the work of Uberoi and Kovasznay). The representation of the wall pressure spectrum used accounts for the effect of a finite sized transducer on the measured wall pressure spectrum. By accounting for the area averaging effect of finite sized transducers on the measured turbulent boundary layer wall pressure spectra, it was possible to use Chase's rigorous formulations for the wavevector-frequency spectrum instead of the point pressure spectrum representations which assume an infinitely small measurement sensor. Results from the numerical integrations are compared to recent experimental data to determine which model of the wavevector- frequency spectrum most accurately predicts measured turbulent boundary layer wall pressure spectra. Data from experiments using fluids with a wide range of physical properties (air, water, and glycerine) are used for comparison purposes. Using the selected model, new empirical constants are established for use in the model for each fluid under consideration. Justification for use of the new empirical constants is given, and current limitations of the wavevector- frequency models are discussed.

Author: Virgil A. Sandborn
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 168

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