Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
Experimental Study of Unsteady Turbulent Boundary Layers
Author: Experimental Study of the Fluid Mechanics of Unsteady Turbulent Boundary Layers
Author: Giles John BreretonPublisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 304
Book Description
An experimental study of the effects of forced, free-stream unsteadiness on turbulent boundary layers was undertaken in an effort to characterize the nature of such flows and to provide guidance for turbulence modelers. A turbulent boundary layer, which had developed under steady, constant-pressure conditions, was locally subjected to a range of frequencies of sinusoidal free-stream unsteadiness. The response of the boundary layer to these free-stream effects was studied through simultaneous measurements of the u and v components of the velocity field, using a two-color laser-doppler anemometer. To focus on the distinct behaviors of the deterministic and time-averaged fields of flow, the equations of fluid motion were reformulated according to a triple decomposition of velocity and pressure into; (i) a time-averaged measure, (ii) a deterministic or organized, unsteady measure, and (iii) a turbulent measure.
An Experimental Study of the Dynamics of an Unsteady Turbulent Boundary Layer
Author: Stanford University. Thermosciences DivisionPublisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 226
Book Description
Experimental Study of Unsteady Separating Turbulent Boundary Layers
Author: N. K. AgarwalPublisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 189
Book Description
A detailed experimental study of two large amplitude unsteady freestream flows and a third unsteady flow produced by an oscillating roof damper is reported. Detailed ensemble-averaged velocity and turbulence measurements were made using hot-wire and laser anemometers. While the primary function of this report is to present and document these data, some discussion of the results and a number of data plots are presented. The reduced data are available on computer diskettes. Upstream of detachment at the phases with no flow reversal, the flows are quasi-steady. For the large amplitude flows, at low velocity phases some flow reversal occurs upstream of detachment, which was not observed in the moderate amplitude flow studied by Simpson et al. (1983). After the beginning of detachment, large amplitude and phase variations develop through each flow. Huge backflow velocities, as large as free-stream, were measured. Keywords: Unsteady flows, Laser anemometry, Turbulence, Separation.
Experimental Study of the Effect of Streamwise Vortices on Unsteady Turbulent Boundary-layer Separation
Author: W. W. HumphreysPublisher:
ISBN:
Category :
Languages : en
Pages : 296
Book Description
This experiment studied the effect of streamwise vortices on unsteady turbulent boundary-layer separation. The objectives were to document the flow field, to characterize the time response of the boundary layer, and to understand the actual mechanisms by which the streamwise vortices modify boundary-layer behavior. A new configuration for non-obtrusive three-component Laser Doppler Anemometry (LDA) determined the phase averaged velocity and Reynolds stress components, in an unsteady water tunnel, at a momentum thickness Reynolds number of 1840. The streamwise vortices were created by three pairs of half-delta wing vortex generators, while the boundary-layer separation was controlled through impulsively initiated opposite-wall suction, which created a strong adverse pressure gradient. The time response of the freestream velocity demonstrates that convection is the primary mechanism by which vortex generators modify the response of the boundary layer. There is an initial fast response throughout the boundary layer which is unaffected by the presence of vortex generators, followed by a slow or convective response, the magnitude of which is substantially modified by the presence of the vortex generators. Flow control, Unsteady turbulent layers. Aircraft, Vortex generators. (jes).
An Experimental Study of the Effect of Streamwise Vortices on Unsteady Turbulent Boundary-layer Separation
Author: William W. HumphreysPublisher:
ISBN:
Category :
Languages : en
Pages : 502
Book Description
A Compilation of Unsteady Turbulent Boundary Layer Experimental Data
Author: Lawrence W. CarrPublisher:
ISBN:
Category : Turbulence
Languages : en
Pages : 62
Book Description
A comprehensive literature search was conducted and those experiments related to unsteady turbulent boundary-layer behavior were cataloged. In addition, an international survey of industrial, university, and government research laboratories was made, in which new and ongoing experimental programs associated with unsteady turbulent boundary-layer research were identified. Pertinent references were reviewed and classified based on the technical emphasis of the various experiments that include instantaneous or ensemble-averaged profiles of boundary-layer variables are stressed. Detailed reviews that include descriptions of the experimental apparatus, flow conditions, summaries of acquired data, and significant conclusions are made. The measurements made in these experiments that exist in digital form have been stored on magnetic tape, and instructions are presented for accessing these data sets for further analysis. (Author).
Standardization of Computational Experiments in Unsteady Turbulent Boundary-layer Flow
Author: Compilation of unsteady turbulent boundary layer experimental data
Author: Study of Unsteady Turbulent Boundary Layers
Author: Angel Nicolas MenendezPublisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 226
Book Description
A turbulent boundary layer, subjected to a free-stream velocity which changes sinusiodally in time under a zero time mean pressure gradient, is studied both experimentally and analytically. Using a two-component Laser Doppler Anemometer and a Heat Flux Gage, detailed and high quality information is obtained on the instantaneous velocity distribution and wall shear stress, respectively, at various stations. An asymptotic theory, for large Reynolds numbers, is developed for the oscillatory motion. It is valid for both boundary layers at arbitrary time-mean pressure gradients and fully developed pipe and channel flow, and is successfully applied to the present and previous available experimental information. The theory identifies two frequency parameters, in terms of which four different frequency regimes are defined. Similarity laws are identified for each one of these frequency regimes. All the experimental data have been archived on magnetic tape. (Author).