Author: Olivia R. DawsonPublisher:
ISBN:
Category : Vortex-motion
Languages : en
Pages : 40
Book Description
The Effect of Persistent Vortices on Boundary Layer Behavior in Flow Along a Wavy Wall
Author: Olivia R. DawsonPublisher:
ISBN:
Category : Vortex-motion
Languages : en
Pages : 40
Book Description
The Effect of Persistent Vortices on Boundary Layer Behavior in Turbulent Flow Along a Kelvin-Stuart Cat's Eyes Wavy Wall
Author: Amir MehmedagicPublisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 35
Book Description
The vortex persistence theory predicts that the addition of a sufficiently strong, stationary vortex near a wall will reduce the wall fluxes in turbulent flows. To test the theory flow visualization and hot-wire experiments in a water tunnel at moderate Reynolds number reveal that a persistent vortex will relaminarize the boundary layer along wavy even in the presence of freestream turbulence. This result is consistent with Dawson [7] who found similar boundary layer behavior using a von Karman separatrix shaped wavy wall, and Balle [2], who's results showed laminar wall heat fluxes under stationary vortices using the von Karman wavy wall. Based on Dawson's flow visualization, and following Balle's analogy, the separatrix of a Kelvin-Stuart Cat's Eyes flow pattern was replaced with a solid wavy wall to stabilize the vortices shed by an array of half-delta vortex generators just upstream of the leading edge of the wavy wall. The correct angle of the array allows for persistent vortices to traverse along the grooves of the wavy wall, and displacing the array even slightly yields different turbulent fluxes. The present flow visualization and hot-wire anemometry results suggest that using the cat's eyes wavy wall gives better relaminarization properties than the von Karman shaped wavy wall, which can have many real world applications.
Experimental Study of the Effect of Streamwise Vortices on Unsteady Turbulent Boundary-layer Separation
Author: W. W. HumphreysPublisher:
ISBN:
Category :
Languages : en
Pages : 296
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).
Analysis of Turbulent Boundary Layers
Author: Tuncer CebeciPublisher: Elsevier
ISBN: 0323151051
Category : Technology & Engineering
Languages : en
Pages : 423
Book Description
Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculating two-dimensional and axisymmetric laminar and turbulent boundary layers. This book will be useful to readers who have advanced knowledge in fluid mechanics, especially to engineers who study the important problems of design.
An Investigation of Boundary Layer Behavior on Wavy Walls
Author: Suxun LiLegislazione e controllo igienico del latte in Svizzera
Author: Scientific and Technical Aerospace Reports
Author: Effects of Near Wall Vortex Perturbation in an Array on the Induced Velocity and Pressure
Author: Aditya SridharPublisher:
ISBN:
Category : Perturbation (Quantum dynamics)
Languages : en
Pages : 54
Book Description
When stationary streamwise vortices are introduced in a turbulent boundary layer, previous flow visualization studies revealed that the flow can be partially relaminarized. To study this phenomenon, and the wall pressure signature of the vortices for detecting unstable departures from equilibrium in active flow control systems, it is important to understand the behavior of vortices near the wall, as well as their locally-induced velocity and pressure gradients. A relatively simple potential flow field with multiple point vortices is calculated, using the method of images, where for each vortex, a virtual vortex of equal strength and distance from the wall, but with opposite rotation, was introduced in the domain. The induced velocity and coefficient of pressure on the wall are sinusoidal are dependent on the vortex position and the array configuration; i.e., the span of the vortices (i.e., the distance between the vortex cores) and the height of the vortices from the wall. The effects of center-pair vortex perturbation in different directions on the induced velocity and pressure coefficient on the wall was also investigated.
An Experimental Investigation of Turbulent Boundary Layers Along Curved Surfaces
Author: Ronald M. C. SoPublisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 276
Book Description
Self-sustaining Mechanisms of Wall Turbulence
Author: Ronald Lee PantonPublisher: Computational Mechanics
ISBN:
Category : Science
Languages : en
Pages : 448
Book Description
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.