Download or read book Properties of the Fluctuating Wall Pressure Field of a Turbulent Boundary Layer written by M. K. Bull and published by . This book was released on 1963 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of measurements of various statistical properties of the fluctuating wall-pressure field associated with turbulent subsonic boundary layer flow in conditions covering a range of values of boundary layer thickness and flow speed are given. The measured quantities include overall rms pressures, frequency spectra, and longitudinal and lateral space-time correlations in both broad and narrow frequency bands. Some experimental values of space-time correlation between wall-pressure fluctuations and turbulent velocity fluctautions at various positions in the boundary layer are also presented. These experimental results and some of their implications on the structure of the wallpressure field and the nature of its convection and decay are discussed. (Author).

Download or read book Wall Pressure Fluctuations in a Turbulent Boundary Layer written by William W. Willmarth and published by . This book was released on 1958 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: When a turbulent boundary layer is produced by air flow past a solid surface, the turbulence in the boundary layer can generate a sound field in the free stream and will also induce fluctuating loads on the solid surface. If the surface is flexible, this motion will generate an additional sound field on both sides of the surface. In an initial investigation of the latter form of sound generation, suitable equipment has been developed to measure the fluctuating wall pressure in the turbulent boundary layer. The equipment includes a specially designed low-noise and low-turbulence-level wind tunnel and a small barium titanate transducer and preamplifier combination for frequencies up to 50 kilocycles. The transducer and preamplifier may be useful for other applications. Using this equipment, some of the properties of the wall pressure fluctuations in a turbulent boundary layer have been measured. It was found that the spectrum of the wall pressure fluctuations extended to 50 kilocycles and that the root-mean-square wall pressure was a constant part (0.0035) of the free stream dynamic pressure for 0.2

Download or read book Wall pressure Fluctuations and Pressure velocity Correlations in a Turbulent Boundary Layer written by John S. Serafini and published by . This book was released on 1963 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Pressure Fluctuations in Turbulent Boundary Layers written by M. V. Lowson and published by . This book was released on 1965 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulation of Turbulent Boundary Layer Wall Pressure Fluctuations written by Robert L. Ash and published by . This book was released on 1985 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Monte Carlo simulation of an unsteady, two-dimensional wall pressure field has been developed. The simulation has been evaluated in terms of the statistical properties measured in a variety of turbulent boundary layer experiments and the results are generally in good agreement. Since identifical pressure histories can be created using simulations, it has been possible to investigate the influence of receiver area (or 'microphone' size) on the statistical measurements of identical pressure histories. Based on these simulations, it was possible to conclude that the root mean square pressure levels increase in a quasi linear manner as the receiver size decreases. The trend is in substantial agreement with the experiments of Bull and Thomas, but the threshold of the diameter effect and the magnitude of the r.m.s. increase may be controlled by flow phenomena that are either ignored or improperly simulated. The power spectra are insensitive to receiver size in the energy containing frequency interval. Two-point correlations first show higher correlations with decreasing receiver size, then show poorer correlations as the receiver size becomes small enough to sense fine scale phenomena. The authors believe this simulation computer program can be valuable in studying the response of complex or non-linear structures to quasi-random wall pressure fields. The ability to adjust resolution and simulated flow conditions arbitrarily make it a flexible tool in the analyzing and designing fluid-structural systems.

Download or read book Fluctuating Properties of Turbulent Boundary Layers for Mach Numbers Up to 9 written by William D. Harvey and published by . This book was released on 1969 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluctuating properties of turbulent boundary layers for Mach numbers up to 9.

Download or read book Some Measurements of Longitudinal Space time Correlations of Wall Pressure Fluctuations in Turbulent Pipe Flow written by William Anton Von Winkle and published by . This book was released on 1961 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements made on some of the characteristics of the turbulent pressure field at the wall of a cylindrical pipe yielded root-mean-square pressure levels, power spectra, longitudinal space-time correlations, and convection velocity over a limited range of Reynolds number. The root-mean-square pressure levels were proportional to the dynamic pressure and when nondimensionalized by use of the dynamic pressure were observed to be independent of the Reynolds number and approximately equal to 0.008 over the Reynolds number range examined. The measurements indicate the existence of an apparent downstrea c nvection of the pressure field at a rate which is approximately the mean discharge velocity of the pipe flow. The pressure field in addition to being convected was also dispersed. Estimates of the scale of the turbulence were obtained. A limited statistical analysis of the pressure time history indicates that the amplitude variation is Gaussian. (Author).

Download or read book Coherent Structures and Wall pressure Fluctuations Modeling in Turbulent Boundary Layers Subjected to Pressure Gradients written by Miloud Alaoui and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow around vehicles creates a turbulent boundary layer in the vicinity of the wall. The turbulent behavior induces pressure fluctuations that make the panels vibrate. These vibrations are then transmitted though the structure of the vehicle and radiate noise inside the cabin. The flow-induced noise levels increase with the speed of the vehicle. For this reason, aircraft manufacturers show a great interest in this topic.There are two objectives for this thesis: understand the mechanisms responsible for the wall-pressure fluctuations and predict this source of aircraft panel excitation.A study of available Large Eddy Simulation (LES) computations was performed. The database consists in simulations of turbulent boundary layer flows submitted to favorable, adverse and zero pressure gradients. This is necessary to understand the nature of the flow over curved geometries such as the aircraft flight deck. The effect of pressure gradients on coherent hairpin structures and hairpin packets could be identified and quantified based on visualization and statistical analysis methods. Linear stochastic estimation of the velocity fields revealed a pair of counter-rotating streamwise vortices above hairpin packets. These vortices have a vorticity opposite to that of the hairpins and an “inverse hairpin” model was proposed.Following the work of Ahn et al. (2010), a stochastic model for wall-pressure spectrum was developed. The idea is to build a stochastic turbulent velocity field using hairpin packets which are subjected to a mean flow. The characteristics of the packets depending on the pressure gradient are based on the analyses of the LES database. The pressure field at the wall is obtained by solving a Poisson equation. The results of the hairpin packet model are compared to numerical and experimental data. Finally, the model is used as input for a Statistical Energy Analysis (SEA) simulation in order to predict the levels of vibrations of panels submitted to a turbulent boundary layer flow over a portion of an aircraft cabin.

Download or read book Some Features of Surface Pressure Fluctuations in Turbulent Boundary Layers with Zero and Favorable Pressure Gradients written by Brian E. McGrath and published by . This book was released on 1987 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Temporal and Spectral Features of Wall Pressure Fluctuations Beneath a Turbulent Boundary Layer written by Carolyn Ceder Karangelen and published by . This book was released on 1991 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wall pressure Fluctuations in a Turbulent Boundary Layer written by John S. Serafini and published by . This book was released on 1962 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurements of the Fluctuating Pressure at the Wall Beneath a Thick Turbulent Boundary Layer written by W. W. Willmarth, C. E. Wooldridge and published by . This book was released on 1962 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Boundary Layer Theory written by Hermann Schlichting (Deceased) and published by Springer. This book was released on 2016-10-04 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new edition of the near-legendary textbook by Schlichting and revised by Gersten presents a comprehensive overview of boundary-layer theory and its application to all areas of fluid mechanics, with particular emphasis on the flow past bodies (e.g. aircraft aerodynamics). The new edition features an updated reference list and over 100 additional changes throughout the book, reflecting the latest advances on the subject.

Download or read book WALL PRESSURE FLUCTUATIONS BENEATH AN AXIALLY SUMMERTRIC TURBULEN BOUNDARY LAYER ON A CYLINDER written by CHI-SHENG YANG, WILLIAM W. WILLMARTH and published by . This book was released on 1969 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Thermal and Hydrodynamic Behavior of Thick Rough wall Turbulent Boundary Layers written by P. M. Ligrani and published by . This book was released on 1979 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thick, fully rough, and transitionally rough turbulent boundary layers were studied in order to investigate the differences between fully rough and transitionally rough behavior and to observe how downstream development affects these flows as the boundary layers become very thick. Measurements included Stanton numbers, skin friction coefficients, mean temperature and velocity profiles, Reynolds stress tensor component profiles, and spectra of the longitudinal velocity fluctuations. Predictions of wall heat transfer, wall shear, and mean profiles were made using a mixing-length and turbulent Prandtl number closure scheme which accounted for the effects of wall roughness in the boundary layer equations. The turbulent layers were artificially thickened using an array of solid obstacles which produced a two-dimensional equilibrium flow field with properties representative of natural bounday layers, at least up to the level of the turbulent correlations on a smooth wall, and to the level of the spectra of longitudinal velocity fluctuations on a rough wall. A rough-wall boundary layer environment was provided in which all measurements of lower order than the turbulence correlations could be discussed regarding the influence of roughness, and considered to have properties representative of natural behavior. (Author).

Download or read book The Structure of Turbulent Shear Flow written by A. A. R. Townsend and published by Cambridge University Press. This book was released on 1976 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.

Download or read book Wall Pressure Fluctuations in Boundary Layer Flow and Response of Simple Structures to Random Pressure Fields written by M. K. Bull and published by . This book was released on 1963 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented for r.m.s. pressure, spectra and broad and narrow band space-time correlations of the wall pressure field of a turbulent boundary layer and of correlations between wall pressure and longitudinal velocity fluctuations. Preliminary results of some similar measurements in the laminar-turbulent transition region of a boundary layer are also given. The report also includes results of measurements of panel response to turbulent boundary layer, jet and siren excitation.