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Vortex Packets In Turbulent Boundary Layers With Application To High Reynolds Number Effects Isolated And Patterned Roughness Near Wall Modeling And Strategies For Drag Reduction
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Book Synopsis Vortex Packets in Turbulent Boundary Layers with Application to High Reynolds Number Effects, Isolated and Patterned Roughness, Near Wall Modeling and Strategies for Drag Reduction by :
Download or read book Vortex Packets in Turbulent Boundary Layers with Application to High Reynolds Number Effects, Isolated and Patterned Roughness, Near Wall Modeling and Strategies for Drag Reduction written by and published by . This book was released on 2001 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scientific goals of this work are to develop a complete physical model of turbulence in wall boundary layers and to develop means of describing and modeling surface roughness effect. We make use of recent developments in our understanding of the mechanistic structure of near wall turbulence for smooth walls at low Reynolds numbers to understand how large Reynolds number and wall roughness affect turbulence. We build upon experimental and computational evidence from smooth walls to extend the mechanistic picture of turbulence based on a paradigm of hierarchy of hairpin packets to high Reynolds number, when roughness effect increases in importance. Both experimental measurements of velocity field in smooth and rough walls and direct numerical simulations of evolution and interaction of hairpin vortices are used.
Book Synopsis Legislazione e controllo igienico del latte in Svizzera by :
Download or read book Legislazione e controllo igienico del latte in Svizzera written by and published by . This book was released on 1969 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Three-dimensional Turbulent Boundary Layers by : O. Sendstad
Download or read book Three-dimensional Turbulent Boundary Layers written by O. Sendstad and published by . This book was released on 1992 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Vortex-Induced Boundary Layer Separation by : Vallorie Jeanne Peridier
Download or read book Vortex-Induced Boundary Layer Separation written by Vallorie Jeanne Peridier and published by . This book was released on 1989 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unsteady boundary-layer separation at high Reynolds numbers, Re, is considered on a theoretical and computational basis. Whenever an external inviscid flow induces a region of adverse pressure gradient near a wall, the development of recirculating eddies in the boundary layer is common. An unsteady viscous-inviscid interaction often follows in the form of a local boundary-layer eruption and abrupt ejection of near-wall vorticity into the external flow. The dynamics of this process, as it develops in an initially thin boundary layer, is considered. As interaction ensues, the flow focuses into a band which progressively narrows in the streamwise direction. The complex flow development is extremely difficult to resolve using conventional Eulerian methods; here the boundary-layer solutions are obtained using Lagrangian methods, wherein trajectories of a large number of fluid particles are computed. The algorithms developed are general but are applied here to the problem of the boundary-layer induced by a two-dimensional vortex above an infinite plane wall. Solutions are obtained for the limit problem Re approaches limit of infinity, and for Re large but finite using an interacting boundary-layer approach. The present results describe the initial stages of a strong unsteady viscous-inviscid interaction; apparently it is necessary to account for the effect of normal pressure variations to continue the interaction. Keywords: Vortices; Turbulent boundary layer; Turbulent bursts; Boundary-layer eruptions; Unsteady interactions; Boundary layer flow separation. (edc).
Book Synopsis Excitation of Boundary-layer Turbulence Through Spark Discharges by : Enrique J. Klein
Download or read book Excitation of Boundary-layer Turbulence Through Spark Discharges written by Enrique J. Klein and published by . This book was released on 1971 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Experimental Investigation of Vortex Generation in a Turbulent Boundary Layer Undergoing Adverse Pressure Gradient by : Victor Zakkay
Download or read book An Experimental Investigation of Vortex Generation in a Turbulent Boundary Layer Undergoing Adverse Pressure Gradient written by Victor Zakkay and published by . This book was released on 1972 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Freestream Turbulence on Wall-bounded Tip Vortex Breakdown and Boundary Layer Stability by : Jack Medzorian
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.
Book Synopsis The Effect of Persistent Vortices on Boundary Layer Behavior in Turbulent Flow Along a Kelvin-Stuart Cat's Eyes Wavy Wall by : Amir Mehmedagic
Download or read book The Effect of Persistent Vortices on Boundary Layer Behavior in Turbulent Flow Along a Kelvin-Stuart Cat's Eyes Wavy Wall written by Amir Mehmedagic and published by . This book was released on 2013 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis A Wind-tunnel Study of Low-speed Turbulent Boundary Layer Flow Over a Rough-to-smooth Surface Transition with and Without Two-dimensional Vortex Generators by : John Patrick Burke
Download or read book A Wind-tunnel Study of Low-speed Turbulent Boundary Layer Flow Over a Rough-to-smooth Surface Transition with and Without Two-dimensional Vortex Generators written by John Patrick Burke and published by . This book was released on 1981 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Interaction of an Embedded Longitudinal Vortex with an Attached, Three-dimensional, Turbulent Boundary Layer by : Stanford University. Thermosciences Division. Thermosciences Division
Download or read book Interaction of an Embedded Longitudinal Vortex with an Attached, Three-dimensional, Turbulent Boundary Layer written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1990 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A turbulent boundary layer at low reynolds number and drag reduction by riblets by : Y.P. Tang
Download or read book A turbulent boundary layer at low reynolds number and drag reduction by riblets written by Y.P. Tang and published by . This book was released on 1991 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulent Boundary Layers by : Helmut E. Weber
Download or read book Turbulent Boundary Layers written by Helmut E. Weber and published by . This book was released on 1979 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Structure of High Reynolds Number Turbulent Boundary Layers, Part A. by :
Download or read book The Structure of High Reynolds Number Turbulent Boundary Layers, Part A. written by and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: We provide a summary of our accomplishments under a three-year 'mini URI' program in collaboration with researchers at Yale and Princeton universities. Whereas the central theme of the program is high Reynolds number wall-bounded turbulence, studies at Penn State included (1) analysis of fundamental issues of scale interactions in high Reynolds number turbulence dynamics, (2) the use of the wavelet decomposition and generalized filtering techniques in describing the relationship between the Fourier-spectral description of scale and the physical-space description of structure, (3) direct numerical simulation of passive scalar sources in low Reynolds number turbulent boundary layers and analysis of scalar evolution in relationship to laboratory data, (4) the relationship between homogeneous turbulent shear flow and the inertial sublayer in high Reynolds number turbulent boundary layers, and (5) the development and application of sophisticated data analysis techniques which intimately combine graphical and quantitative analysis within a fully interactive 'Analytical Environment'. A brief summary of the accomplishments in each area of development is presented. Turbulence, Turbulent boundary layers, Shear flows.
Book Synopsis An Experimental Study of the High Reynolds Number Turbulent Boundary Layer by : Gary Joseph Kunkel
Download or read book An Experimental Study of the High Reynolds Number Turbulent Boundary Layer written by Gary Joseph Kunkel and published by . This book was released on 2003 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Shear-free Turbulent Boundary Layers by : Stanford University. Thermosciences Division. Thermosciences Division
Download or read book Shear-free Turbulent Boundary Layers written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1993 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Three-Dimensional Vortex Interactions in Turbulent Boundary Layers by : C. R. Smith
Download or read book Three-Dimensional Vortex Interactions in Turbulent Boundary Layers written by C. R. Smith and published by . This book was released on 1985 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: A combined analytical experimental program, which has as its continuing objective the detailed investigation of the three dimensional vortex interactions which take place in turbulent boundary layers, is described and the accomplishments detailed. The analytical and numerical studies have examined both the development and characteristics of loop and hairpin vortices in both uniform and shear flows; particular attention has been paid to the strong three dimensional, inviscid viscous interaction of these types of vortical flow structures with wall region fluid. The experimental studies have focussed on the creation & detailed examination of three dimensional hairpin vortices, developing flow visualization patterns for cross-comparison with both the analytical studies and fully turbulent boundary layer flows. A technique for developing quantitative data by image processing of the visualization patterns is also described. Keywords: Turbulent boundary layer; Coherent structure; Flow visualization; Numerical modelling; Vortex wall interactions; Computer aided analysis; Loop vortices; Hairpin vortices.
Book Synopsis Tollmien-Schlichting/vortex Interactions in Compressible Boundary Layer Flows by : Nicholas D. Blackaby
Download or read book Tollmien-Schlichting/vortex Interactions in Compressible Boundary Layer Flows written by Nicholas D. Blackaby and published by . This book was released on 1993 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
