Experimental Study of Turbulence Production Mechanisms in Boundary Layer Flows

Experimental Study of Turbulence Production Mechanisms in Boundary Layer Flows
Author: R. E. Falco
Publisher:
Total Pages: 76
Release: 1985
Genre:
ISBN:

Studies of turbulence structure near a wall show that the production process has many manifestations. Detailed experiments, involving visual information in two mutually orthogonal planes, and simultaneous multiple hot-wire anemometry, along with both experimental and numerical simulations were performed in an attempt to determine the underlying conceptual framework. Results indicate that the wide variety of evolutions observed during the turbulence production process near a wall are all manifestations of the evolution of vortex ring-like eddies with the wall and the wall layer. Additional important evolutions result from the interaction of two of these vortex ring/wall interactions occurring with small spatial and temporal differences. Boundary layer interactions have been divided into (4) classes ranging from weak interactions to ones producing strong turbulence. These classes were simulated experimentally vortex ring/moving wall interactions, and--within the constraints of two-dimensions--qualitatively by simple numerical vortex-in-cell simulations. The instantaneous local thickness of the viscous sublayer and the flow field of the large scale motions play dominant roles in determining which class of evolution is observed.

Experimental Investigation of the Turbulence Production Mechanism in Boundary Layers

Experimental Investigation of the Turbulence Production Mechanism in Boundary Layers
Author: R. E. Falco
Publisher:
Total Pages: 41
Release: 1986
Genre:
ISBN:

Over the past year we have discovered the mechanism of production of the long streaks and a mechanism for creation of vortex ring-like typical eddies, and have demonstrated the occurrence of both within a real turbulent boundary layer. These aspects were the missing links needed to complete the conceptual structural model. This model de-emphasizes the importance of hairpin vortices in wall layer transport. However, experimental determination of the relative importance of each of the elements of the model in low Reynolds number layers is far from complete, and we know very little of the Reynolds number dependence or pressure gradient dependence of the model. What we have learned so far suggests several critical parameters that can be manipulated to control the production of turbulence and hence reduce drag. In the proposed research we want to focus on acquiring additional data to support the rational theory that has been formed so as to provide the basis for determining how much leverage we have in our efforts to control boundary layer turbulence.

Recent Results in Laminar-Turbulent Transition

Recent Results in Laminar-Turbulent Transition
Author: Siegfried Wagner
Publisher: Springer Science & Business Media
Total Pages: 334
Release: 2013-06-05
Genre: Technology & Engineering
ISBN: 3540450602

The 24 papers presented at the international concluding colloquium of the German priority programme (DFG-Verbundschwerpunktprogramm) "Transition", held in April 2002 in Stuttgart. The unique and successful programme ran six years, starting April 1996, and was sponsored mainly by the Deutsche Forschungsgemeinschaft, DFG, but also by the Deutsches Zentrum für Luft-und Raumfahrt, DLR, the Physikalisch-Technische Bundesanstalt Braunschweig, PTB, and Airbus Deutschland. The papers summarise the results of the programme and cover transition mechanisms, transition prediction, transition control, natural transition and measurement techniques, transition - turbulence - separation, and visualisation issues. Three invited papers are devoted to mechanisms of turbulence production, to a general framework of stability, receptivity and control, and a forcing model for receptivity analysis. Almost every transition topic arising in subsonic and transonic flow is covered.

Self-sustaining Mechanisms of Wall Turbulence

Self-sustaining Mechanisms of Wall Turbulence
Author: Ronald Lee Panton
Publisher: Computational Mechanics
Total Pages: 448
Release: 1997
Genre: Science
ISBN:

Why is wall turbulence self-sustaining? In this book well-regarded researchers not only discuss what they know and believe, but also speculate on ideas that still require numerical or experimental testing and verification. An initial brief history of boundary layer structure research is followed by chapters on experimental information and specific topics within the subject. There are then sections on computational aspects.