Experimental Investigation of the Turbulence Production Mechanism in Boundary Layers PDF Download
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Author: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 41
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Book Description
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: R. E. Falco
Publisher:
ISBN:
Category :
Languages : en
Pages : 41
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Book Description
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: S. J. Kline
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 70
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Book Description
Author: Peter W. Runstadler
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 616
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Book Description
Author: Donald Ralph Zimmerman
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 348
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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: Ronald M. C. So
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 276
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Author: Peter William Runstadler (Jr.)
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 342
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Author: Gazi Hasanuzzaman
Publisher: Cuvillier
ISBN: 9783736975583
Category :
Languages : en
Pages : 180
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Book Description
Experimental investigation in turbulent boundary layer flows represents one of the canonical geometries of wall bounded shear flows. Utmost relevance of such experiments, however, is applied in the engineering applications in aerospace and marine industries. In particular, continuous effort is being imparted to explore the underlying physics of the flow in order to develop models for numerical tools and to achieve flow control. Flow control experiments have been widely investigated since 1930's. Several flow control technique has been explored and have shown potential benefit. But the choice of control technique depends largely on the boundary condition and the type of application. Hence, friction drag of subsonic transport aircraft is intended to be reduced within the scope of this Ph. D. topic. Therefore, application of active control method such as microblowing effect in the incompressible, zero pressure gradient turbulent boundary layer was investigated. A series of experiments have been performed in two different wind tunnel facilities. Wind tunnel from Department of Aerodynamics and Fluid Mechanics (LAS) was used for the measurements for moderate Reynolds number range in co-operation with the wind tunnel from Laboratoire de M ́ecanique de Feiret Lille for large Reynolds number range. Measurements are conducted with the help of state-of-the-art techniques such as Laser Doppler Anemometry, Particle Image Velocimetry and electronic pressure sensors.
Author: Alexander Vladimir Lisin
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 164
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Book Description
