The Interaction Between a Non-embedded Longitudinal Vortex and Turbulent Boundary Layer Under the Influence of Streamwise Pressure Gradient PDF Download
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Author: Joseph Creazzo
Publisher:
ISBN:
Category : Longitudinal method
Languages : en
Pages : 602
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Book Description
Author: Joseph Creazzo
Publisher:
ISBN:
Category : Longitudinal method
Languages : en
Pages : 602
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 52
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Book Description
Author: Stanford University. Thermosciences Division. Thermosciences Division
Publisher:
ISBN:
Category :
Languages : en
Pages : 170
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Book Description
Author: Sinnappoo Kanesalingam
Publisher: Springer Nature
ISBN: 9811557500
Category : Technology & Engineering
Languages : en
Pages : 146
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Book Description
This book highlights novel applications of innovative fabrics in the design of an interlayer between the scalp and the helmet lining of motorcycle helmets to control the temperature inside the helmet. It examines various fibre microstructure configurations and fibre treatments in terms of their ability to assist in the dissipation of heat from the scalp. The findings presented here will be of considerable benefit to motorcyclists in South East Asia and other tropical regions.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Book Description
Author: Franklin Dement
Publisher:
ISBN: 9781423546672
Category :
Languages : en
Pages : 178
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Book Description
The Air Force Institute of Technology Boundary Layer Research Facility test section was modified to create controlled non-zero streamwise pressure gradients. The capability of the modified facility to reproduce theoretical laminar boundary layer velocity profiles and to create a self- preserving flow with an adverse streamwise pressure gradient was verified with three-dimensional laser Doppler anemometry. The effects of streamwise adverse and favorable pressure gradients on turbulent boundary layer flow characteristics (velocity profiles, turbulence and skin friction) and vortex formation over a flat plate with riblets at low speed (U = 5 mIs) were studied. Normal and spanwise velocity profiles for both pressure gradients showed the presence of paired counter-rotating vortices nested within the riblet valleys. These flow structures increased drag and significantly altered near-wall flow compared to a smooth plate turbulent boundary layer. The adverse pressure gradient tended to degrade these vortices as the flow progressed.
Author: Albert H. Jeans
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 176
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Book Description
Concave curvature has a relatively large, unpredictable effect on turbulent boundary layers. Some, but not all previous studies suggest that a large-scale, stationary array of counter-rotating vortices exists within the turbulent boundary layer on a concave wall. The objective of the present study was to obtain a qualitative model of the flow field in order to increase our understanding of the underlying physics. A large free-surface water channel was constructed in order to perform a visual study of the flow. Streamwise components of mean velocity and turbulence intensity were measured using a hot film anemometer. The upstream boundary was spanwise uniform with a momentum thickness to radius of curvature of 0.05. Compared to flat wall flow, large-scale, randomly distributed sweeps and ejections were seen in the boundary layer on the concave wall. The sweeps appear to suppress the normal mechanism for turbulence production near the wall by inhibiting the bursting process. The ejections appear to enhance turbulence production in the outer layers as the low speed fluid convected from regions near the wall interacts with the higher speed fluid farther out. The large-scale structures did not occur at fixed spanwise locations, and could not be called roll cells or vortices. (Author).
Author: Franz Durst
Publisher: Springer Science & Business Media
ISBN: 3642714358
Category : Science
Languages : en
Pages : 367
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Book Description
The first four symposia in the series on turbulent shear flows have been held alternately in the United States and Europe with the first and third being held at universities in eastern and western States, respectively. Continuing this pattern, the Fifth Symposium on Turbulent Shear Flows was held at Cornell University, Ithaca, New York, in August 1985. The meeting brought together more than 250 participants from around the world to present the results of new research on turbulent shear flows. It also provided a forum for lively discussions on the implications (practical or academic) of some of the papers. Nearly 100 formal papers and about 20 shorter communications in open forums were presented. In all the areas covered, the meeting helped to underline the vitality of current research into turbulent shear flows whether in experimental, theoretical or numerical studies. The present volume contains 25 of the original symposium presentations. All have been further reviewed and edited and several have been considerably extended since their first presentation. The editors believe that the selection provides papers of archival value that, at the same time, give a representative statement of current research in the four areas covered by this book: - Homogeneous and Simple Flows - Free Flows - Wall Flows - Reacting Flows Each of these sections begins with an introductory article by a distinguished worker in the field.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Longitudinal vortices in turbulent boundary layers that are subjected to strong wall curvature (both convex and concave) and strong adverse pressure gradients were investigated numerically. The motivation for this research was to uncover the fundamental mechanisms responsible for the generation of longitudinal vortices and their dynamical interaction with the other dominant coherent structures that arise from the presence of wall curvature and strong adverse pressure gradients. This understanding is essential for future implementation of separation control techniques for practical flows when longitudinal vortices are inherently present, or when forced longitudinal vortices are employed for separation control (i.e., on demand vortex generators). Furthermore, such investigations can shed light on the turbulence generation mechanisms for boundary layers subjected to streamwise curvature and pressure gradients when longitudinal vortices are present. The investigations were carried out using DNS, LES and unsteady RANS. Towards this end, we have employed our new Flow Simulation Methodology (FSM) for calculating turbulent flows. The present numerical investigations were a critical test for FSM and the turbulence model used in FSM as the investigated flows are highly complex with the turbulence in strong non-equilibrium.
Author: W. W. Humphreys
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
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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).
