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Author: Creighton Lane Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
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: Creighton Lane Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
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 : Fluid dynamics Languages : en Pages : 88
Book Description
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: Peter Bradshaw Publisher: ISBN: Category : Boundary layer Languages : en Pages : 52
Book Description
Surface pressure fluctuations below turbulent boundary layers were studied, in part, because they can be regarded as 'footprints' of passing turbulent eddies. The pressure fluctuations are formally described by a Poisson equation, implying that the pressure fluctuation at a given point is mathematically represented by the integral of a 'source' term over the whole flow field, with a weighting inversely proportional to the distance of the source from the given point. In turbulent boundary layers, fluctuations were made in a low-speed constant pressure the high-frequency part of the wall pressure fluctuations is generated mainly within the inner layer - say, the first 20% of the boundary layer thickness - and the low-frequency part is generated mainly in the outer layer. Measurements of velocity and surface-pressure turbulent boundary layer well downstream of an extensive region of wall roughness. The turbulence near the wall was representative of a smooth-wall flow, while that in the outer layer was typical of the upper stream rough-wall flow. Comparison with previous measurements on an entirely smooth wall illustrates the relative contributions of the inner and outer layers to the surface pressure fluctuations. Further work has been done to compare the VITA (Variable ge) conditional-sampling algorithm withuctuations were more advanced algorithms. Keywords: Turbulent boundary layer, Noise measurement, Statistical analysis, Surface roughness, and VITA algorithm.
Author: Creighton Lane
Author: Creighton Lane
Author: College of Aeronautics (Cranfield, Bedfordshire)
Author: John S. Serafini
Author: Peter Bradshaw
Author: Brian E. McGrath
Author: A. R. Green
Author: John H. Linebarger
Author: G. M. Lilley
Author: Virgil A. Sandborn
Author: Huon Li