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Author : V.M. Gadetskiy
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (11 download)
Download or read book Investigation of the Influence of Vortex Generators on Turbulent Boundary Layer Separation written by V.M. Gadetskiy and published by . This book was released on 1974 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Lindsay J. Lina
Publisher :
ISBN 13 :
Total Pages : 30 pages
Book Rating : 4.:/5 (719 download)
Download or read book A Preliminary Flight Investigation of the Effects of Vortex Generators on Separation Due to Shock written by Lindsay J. Lina and published by . This book was released on 1950 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A preliminary investigation was made of an airplane in flight to determine the effectiveness of vortex generators in preventing separation due to compressibility shock at full-scale Reynolds numbers. Several arrangements of vortex generators were tested at 10 and 30 percent chord on the upper surface between 44 and 61 percent semispan on a wing of an F-51D airplane. The wing contour over this portion of the span was modified for other tests and indicated earlier flow separation than the original contour. The vortex generators, consisting of small airfoils of rectangular plan form mounted normal to the surface, were arranged in a spanwise row and set at an angle of attack of about 15 degrees, so as to produce a system of vortices for the purpose of increasing the transfer of momentum into the turbulent boundary layer.
Author : W. W. Humphreys
Publisher :
ISBN 13 :
Total Pages : 296 pages
Book Rating : 4.F/5 ( download)
Download or read book Experimental Study of the Effect of Streamwise Vortices on Unsteady Turbulent Boundary-layer Separation written by W. W. Humphreys and published by . This book was released on 1988 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Author : Jinjun Wang
Publisher : Cambridge University Press
ISBN 13 : 1107161568
Total Pages : 293 pages
Book Rating : 4.1/5 (71 download)
Download or read book Flow Control Techniques and Applications written by Jinjun Wang and published by Cambridge University Press. This book was released on 2018-12-13 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master the theory, applications and control mechanisms of flow control techniques.
Author : Coleman duP. Donaldson
Publisher :
ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.3/5 (91 download)
Download or read book Investigation of a Simple Device for Preventing Separation Due to Shock and Boundary-layer Interaction written by Coleman duP. Donaldson and published by . This book was released on 1950 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented of a preliminary investigation of vortex generators introduced into the region of boundary layer to increase the turbulent mixing, in an attempt to prevent separation due to boundary-layer and shock interaction. Prevention of such separation and some of its adverse effects up to Mach numbers ahead of the shock of the order of 1.4 appears possible by means of this simple device. Preliminary flight tests show that this method is effective in controlling shock-induced separation on the wing of an airplane at high speed.
Author : Holger Babinsky
Publisher : Cambridge University Press
ISBN 13 : 1139498649
Total Pages : 481 pages
Book Rating : 4.1/5 (394 download)
Download or read book Shock Wave-Boundary-Layer Interactions written by Holger Babinsky and published by Cambridge University Press. This book was released on 2011-09-12 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.
Author : National Aeronautics and Space Adm Nasa
Publisher : Independently Published
ISBN 13 : 9781793967527
Total Pages : 34 pages
Book Rating : 4.9/5 (675 download)
Download or read book Boundary Layer Flow Control by an Array of Ramp-Shaped Vortex Generators written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-13 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control. (See CASI ID 20120009374 for Supplemental CD-ROM.) Zaman, K. B. M. Q. and Hirt, S. M. and Bencic, T. J. Glenn Research Center NASA/TM-2012-217437, E-18130
Author : National Aeronaut Administration (Nasa)
Publisher :
ISBN 13 :
Total Pages : 32 pages
Book Rating : 4.6/5 (711 download)
Download or read book Boundary Layer Flow Control by an Array of Ramp-Shaped Vortex Generators written by National Aeronaut Administration (Nasa) and published by . This book was released on 2020-08-03 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control. (See CASI ID 20120009374 for Supplemental CD-ROM.) Zaman, K. B. M. Q. and Hirt, S. M. and Bencic, T. J. Glenn Research Center NASA/TM-2012-217437, E-18130 WBS 561581.02.08.03.47.06.03 VORTEX GENERATORS; VORTICITY; TURBULENT BOUNDARY LAYER; WIND TUNNEL TESTS; BOUNDARY LAYER SEPARATION; FLOW DISTRIBUTION; VELOCITY MEASUREMENT; UPSTREAM; DOWNWASH; LOW SPEED
Author : Nasa Technical Reports Server (Ntrs)
Publisher : BiblioGov
ISBN 13 : 9781289168520
Total Pages : 36 pages
Book Rating : 4.1/5 (685 download)
Download or read book Boundary Layer Flow Control by an Array of Ramp-Shaped Vortex Generators written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-07 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control.
Author : John C. Lin
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Control of Turbulent Boundary-layer Separation Using Micro-vortex Generators written by John C. Lin and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Martin Kiran Rao
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (63 download)
Download or read book An Experimental Investigation of the Use of Air Jet Vortex Generators to Control Shock Induced Boundary Layer Separation written by Martin Kiran Rao and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Ola Lögdberg
Publisher :
ISBN 13 : 9789171784681
Total Pages : 110 pages
Book Rating : 4.7/5 (846 download)
Download or read book Vortex Generators and Turbulent Boundary Layer Separation Control written by Ola Lögdberg and published by . This book was released on 2006 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul K. Chang
Publisher :
ISBN 13 :
Total Pages : 42 pages
Book Rating : 4.:/5 (227 download)
Download or read book Computation of the Turbulent Boundary Layer Downstream of Vortex Generators written by Paul K. Chang and published by . This book was released on 1987 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The approximate analysis of three-dimensional incompressible turbulent boundary layer downstream of vortex generators is presented. Extensive numerical computations are carried out to assess the effectiveness of single-row, counter-rotating vane-type vortex generators to alleviate flow separation lines. Flow separation downstream of the vortex generators on a thick airfoil are determined in terms of size, location, and arrangement of the vortex generators. These lines are compared with the separation line without the vortex generators. High efficiency is obtained with the moderately slender rectangular blade of the generator. The results indicate that separations is alleviated more effectively in the region closer to the symmetry axis of the generator than in the outer region of the symmetry axis. No optimum conditions for the alleviation of flow separation are established in this investigation, and no comparisons are made with other analytical results and experimental data. Keywords: Boundary layer computations, Flow separation, Vortex generators.
Download or read book Investigation of a Sub Boundary Layer Vortex Generator for the Control of Separation in Boundary Layer-shock Wave Interaction written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Unai Fernández Gámiz
Publisher :
ISBN 13 :
Total Pages : 127 pages
Book Rating : 4.:/5 (112 download)
Download or read book Fluid Dynamic Characterization of Vortex Generators and Two-dimensional Turbulent Wakes written by Unai Fernández Gámiz and published by . This book was released on 2014 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this PhD thesis is the fluid dynamic characterization of the flow behind vortex generators (VG) as well as to investigate their influence in the separation of the boundary layer. CFD simulations have been carried out for the analysis of the flow downstream a single vortex generator on a flat plate. In order to evaluate the induced flow effect of the VG, a test case of a single rectangular VG has been designed and the flow have been numerically simulated and analyzed. Three-Dimensional steady state simulations at low Reynolds number have been performed using EllipSys3D CFD code and the computational results have been compared with experimental data. The self-similar behavior and the helical symmetry on the VG induced flow have been studied. The computations have demonstrated considerable reliability when reproducing the physics of the VG by a rectangular vortex generator. Furthermore, a detailed analysis of the equilibrium parameters has been made on a two-dimensional turbulent wake in two different test cases: a twin-plate and a symmetric airfoil (NACA0012). Both cases have been numerically analyzed and the computational results have been compared with experimental observations. The self-similar behaviour on the wake generated by a twin-plate and a symmetric airfoil has been tested and the CFD results match the experimental observations reasonably well.This thesis has been divided into five main parts:PART I. In this part is presented the importance of this research as well as the main motivation to carry out such work. An extensive description of the state of the art on vortex generators models is presented with high emphasis on wind turbine applications. Further, a very detailed explanation of the state of the art on self-similarity and on two-dimensional turbulent wake equilibrium is given.PART II. The three chapters of this part comprise the foundation of this thesis. In this part there is a detailed description of the vortex generator models used in this research, as well as a comparison of the computational results with the wind tunnel experiments carried out by Clara M. Velte, as a validation tool of the computations. The implementation of the BAY model into the EllipSys CFD code is described in Chapter 5 and it was performed in conjunction with N.N. S?rensen and P.E. Rethore. Finally a parametric study of the device angle dependency of a single VG on a flat plate is described in Chapter 7. Four different angles of attack have been selected for this parametric study: 20o, 25o, 30o and 35o.PART III. In this part, a self-similarity analysis has been made on a single rectangular VG on a flat plate. The simulations were able to capture the helical behaviour of the vortex generator wake with good accuracy when comparing with the experimental data. A very detailed description of the downstream evolution of the helical parameters in the computations is presented in this chapter 8 and compared with experimental results.
Author : Chaoqun Liu
Publisher : Academic Press
ISBN 13 : 0128190248
Total Pages : 458 pages
Book Rating : 4.1/5 (281 download)
Download or read book Liutex and Its Applications in Turbulence Research written by Chaoqun Liu and published by Academic Press. This book was released on 2020-10-29 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liutex and Its Applications in Turbulence Research reviews the history of vortex definition, provides an accurate mathematical definition of vortices, and explains their applications in flow transition, turbulent flow, flow control, and turbulent flow experiments. The book explains the term "Rortex" as a mathematically defined rigid rotation of fluids or vortex, which could help solve many longstanding problems in turbulence research. The accurate mathematical definition of the vortex is important in a range of industrial contexts, including aerospace, turbine machinery, combustion, and electronic cooling systems, so there are many areas of research that can benefit from the innovations described here. This book provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence. Important theory and methodologies used for developing these laws are described in detail, including: the classification of the conventional turbulent boundary layer concept based on proper velocity scaling; the methodology for identification of the scales of velocity, temperature, and length needed to establish the law; and the discovery, proof, and strict validations of the laws, with both Reynolds and Prandtl number independency properties using DNS data. The establishment of these statistical laws is important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence. Provides an accurate mathematical definition of vortices Provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence Explains the term “Rortex as a mathematically defined rigid rotation of fluids or vortex Covers the statistical laws important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence
Author : Jack Medzorian
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)
Download or read book Effect of Freestream Turbulence on Wall-bounded Tip Vortex Breakdown and Boundary Layer Stability written by Jack Medzorian and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wall-bounded tip vortices appear in a variety of aerodynamic applications, such as, aircraft engines, inlet S-ducts, turbomachinery tip leakage, and vortex generators used for flow separation control. Studies show that vortex flows with high swirl that are exposed to a sufficient adverse pressure gradient will trigger the onset of vortex instability. However, it is not known whether the addition of freestream turbulence or the presence of a wall will stabilize a vortex due to momentum entrainment or trigger early bursting via amplification of an instability pathway. In this study, a wall-bounded vortex is analyzed in a low-speed wind tunnel to evaluate the effects that adverse pressure gradient and freestream turbulence have on vortex stability boundaries. Experimental techniques such as high-speed stereoscopic particle image velocity is used to capture three-dimensional flow fields of the wall bounded vortex. In addition to the PIV measurements, point measurements are taken using Laser Doppler Velocimetry to obtain turbulent characterization of the freestream and boundary layer flow. The results in this study predict an increase in vortex stability with freestream turbulence. Near a wall, further increases in vortex stability is depicted due to increased diffusion and reduction in rotational momentum. Furthermore, turbulent kinetic energy in a vortex core is decreased in high freestream turbulence when the vortex is near a wall due to a reduction in roll up and entrainment of high turbulence that exists in turbulent boundary layers near the wall. Turbulent boundary layers exposed to high freestream turbulence and adverse pressure gradients appear in a variety of aerodynamic application such as the suction side of airfoils within gas turbine engines and on aircraft wings. Non-equilibrium turbulent boundary layers exposed to a non-constant adverse pressure gradient have been shown to influence the outer region of the mean boundary layer profile due to the resilience of larger scale superstructures. However, it is not known whether the addition of freestream turbulence will increase the effect of history in a turbulent boundary layer due to increased entrainment of larger scales or decrease in effects from breakdown of these superstructures in the freestream. In this study, an experimental technique known as laser Doppler velocimetry is applied to obtain 2-dimensional, high-speed velocity measurements used for capturing mean profiles, turbulent statistics, and turbulent characterization of the freestream flow. The results in this study predict that pressure gradient history effects can have influence on Reynolds stress distributions past the outer region and into the log-region of the boundary layer due to diffusion of turbulence towards the wall. Additionally, pressure gradient effects, and thus the effects of a boundary layer's history, are significantly reduced when subjected to freestream turbulence due to dominant influence of turbulence within the wake region. Lastly, turbulent statistics show that a straight contoured wall, containing a smaller local pressure gradient but sustained over longer distance, has a greater adverse pressure gradient effect on a boundary relative to concave or convex contouring.
