Journal ArticleDOI
Detrimental Effects of Almost Immeasurably Small Freestream Nonuniformities Generated by Wind-Tunnel Screens
TLDR
In this article, measurements were obtained during the course of a series of flow quality improvements to a small stand-alone wind tunnel that has been modified for boundary-layer transition studies.Abstract:
Measurements are presented that were obtained during the course of a series of flow quality improvements to a small stand-alone wind tunnel that has been modified for boundary-layer transition studies. The objective of establishing a Blasius boundary layer with a high degree of spanwise uniformity has been frustrated by the persistence of Klebanoff modes, i.e., weak streamwise vortices within the layer. The vortices originate at the leading edge and appear to be caused by almost immeasurably small nonuniformities in the freestream introduced by the wind-tunnel screens. The vortices cause a spanwise thickening and thinning of the layer. Contours of the background unsteadiness in a spanwise plane through the layer show locally concentrated regions with elevated levels that are associated with the vortices. These contours are used as a sensitive indicator for the flow quality improvements. Although far from forming a complete parametric study, the observations should act as a valuable guide for others. For example, spanwise variations in the porosity of the screens were discovered by traversing each screen between a laser and a photo detector. Significant improvement in the spanwise uniformity of the layer was obtained by sorting the screens based on these resultsread more
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Reference EntryDOI
Fundamentals of Wind-Tunnel Design
TL;DR: In this paper, the fundamentals of low-speed wind tunnel design are discussed, as well as the specific measurement requirements and the various space, budget, and power constraints that guide the tunnel design.
Journal ArticleDOI
On the Environmental Realizability of Algebraically Growing Disturbances and Their Relation to Klebanoff Modes
TL;DR: In this article, a theoretical explanation of some experimentally observed phenomena associated with the so-called Klebanoff modes is obtained by analyzing the flow over a finite thickness flat plate resulting from a small-amplitude distortion imposed on the upstream mean flow.
Journal ArticleDOI
Linear and nonlinear instabilities of a Blasius boundary layer perturbed by streamwise vortices. Part 2. Intermittent instability induced by long-wavelength Klebanoff modes
Xuesong Wu,Meelan M. Choudhari +1 more
TL;DR: In this paper, the stability properties of a Blasius boundary layer perturbed by Klebanoff distortions with a relatively long spanwise scale were investigated and it was shown that the instability is intermittent in time and localised in space, being confined to a finite part of the Kleinbanoff mode cycle and to a specific window along the streamwise direction.
Proceedings ArticleDOI
Design, Fabrication, and Characterization of an Anechoic Wind Tunnel Facility
TL;DR: In this article, the design, fabrication, and preliminary characterization of an anechoic wind tunnel facility at the University of Florida is presented, which is used for airframe noise analysis.
References
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TL;DR: In this article, an experimental investigation is described, in which principal emphasis is given to revealing the nature of the motions in the non-linear range of boundary-layer instability and the onset of turbulence, and it is demonstrated that the actual breakdown of the wave motion into turbulence is a consequence of a new instability which arises in the aforementioned three-dimensional wave motion.
Journal ArticleDOI
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Journal ArticleDOI
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E. M. Laws,J. L. Livesey +1 more
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Proceedings ArticleDOI
Experimental study of disturbances produced in a pre-transitional laminar boundary layer by weak freestream turbulence
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