An Experimental Study of Turbulence Production Mechanisms in Boundary Layer Flows PDF Download
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Author: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
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The major goal of this research has been to identify the mechanisms responsible for turbulence production near smooth walls. Although many dynaical features of the turbulence production process have been previously identified, and many models proposed to explain how these features came to be, the reasons for their existence, and for their evolution into turbulent eruptions are stil not satisfactorily understood. The coherence associated with the production of turbulence near a wall is greater than anticipated before this investigation began. It is clear that many aspects of the physics can be modelled by the vortex ring/wall interaction, however, it appears that somewhat less stringent conditions can also initiate new production. Furthermore, the same physics appears to govern production for Reynolds numbers up to the onset of the law of the wake (which signals the onset of high Reynolds number asymptotic behavior). However, further investigation is required to determine which details of the interactions are necessary and which are sufficient, before attempts at logically modifying the production rate can be made.
Author: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
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Book Description
The major goal of this research has been to identify the mechanisms responsible for turbulence production near smooth walls. Although many dynaical features of the turbulence production process have been previously identified, and many models proposed to explain how these features came to be, the reasons for their existence, and for their evolution into turbulent eruptions are stil not satisfactorily understood. The coherence associated with the production of turbulence near a wall is greater than anticipated before this investigation began. It is clear that many aspects of the physics can be modelled by the vortex ring/wall interaction, however, it appears that somewhat less stringent conditions can also initiate new production. Furthermore, the same physics appears to govern production for Reynolds numbers up to the onset of the law of the wake (which signals the onset of high Reynolds number asymptotic behavior). However, further investigation is required to determine which details of the interactions are necessary and which are sufficient, before attempts at logically modifying the production rate can be made.
Author: Robert Edward Falco
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 18
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Author: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 76
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Book Description
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.
Author: Heung-tae Kim
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 188
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The structure of the turbulent boundary layer on a smooth wall with zero pressure gradient has been studied experimentally. Emphasis has been given to the production of turbulence in the inner layers. Intensive studies of a few.
Author: S. J. Kline
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 70
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Author: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 41
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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.
Author: Weijie Shao
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Siegfried Wagner
Publisher: Springer Science & Business Media
ISBN: 3540450602
Category : Technology & Engineering
Languages : en
Pages : 334
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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.
Author: James Hassler Strickland
Publisher:
ISBN:
Category : Boundary layer control
Languages : en
Pages : 430
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Author: Peter William Runstadler (Jr.)
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 342
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