Download or read book A Robust Scheme for Control of Skin Friction and Heat Transfer in Turbulent Boundary Layers Via a New Instability Mechanism written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using direct numerical simulations of turbulent channel flow, we present new insight into the generation of streamwise vortices near the wall, and an associated drag reduction strategy. Growth of x-dependent spanwise velocity disturbances w(x) is shown to occur via two mechanisms: (i) linear transient growth, which dominates early-time evolution, and (ii) linear normal-mode instability, dominant asymptotically at late time (for frozen base flow streaks). Approximately 25% of streaks extracted from near-wall turbulence are shown to be strong enough for linear instability (above a critical vortex line Lift angle). However, due to viscous annihilation of streak normal vorticity COy, normal mode growth ceases after a factor of two energy growth. In contrast, the linear transient disturbance produces a 20-fold amplification, due to its rapid, early-time growth before significant viscous streak decay. Thus, linear transient growth of w(x) is revealed as a new, apparently dominant, generation mechanism of x-dependent turbulent energy near the wall.

Download or read book A Robust Scheme for Control of Skin Friction and Heat Transfer in Turbulent Boundary Layers Via New Instability Mechanism written by Fazle Hussain and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using direct numerical simulations of turbulent channel flow, we present a new method for skin friction reduction by prevention of streamwise vortex formation near the wall. Based on recent evidence of streak instability-induced vortex generation, we develop a new technique for drag reduction, enabling large-scale flow forcing without requiring instantaneous flow information. As proof-of-principle, x-independent forcing, with a wavelength of 400 wall units and an amplitude of only 6% of the centerline velocity, produces a significant sustained drag reduction 20% for imposed counterrotating streamwise vortices and 50% for colliding, z-directed wall jets. The drag reduction results from weakened longitudinal vortices near the wall, due to forcing-induced suppression of the underlying streak instability. In particular, the forcing significantly weakens the wall-normal vorticity flanking lifted low-speed streaks, thereby arresting the streaks' instability responsible for vortex generation. These results suggest promising new drag reduction strategies, e.g., passive vortex generators or colliding spanwise jets from x-aligned slots, involving large-scale (hence more durable) actuation and requiring no wall sensors or control logic.

Download or read book A Correlation of Heat transfer and Skin friction Data and an Experimental Reynolds Analogy Factor for Highly Cooled Turbulent Boundary Layers at Mach 5 0 written by Donald M. Wilson and published by . This book was released on 1969 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent boundary-layer heat transfer and skin-friction coefficients were measured on sharp slender cones at a free-stream Mach number of 5.0. Wall-to-stagnation temperature ratios from 0.15 to 0.80 were obtained by precooling or preheating the model. Tests were conducted for a wide range of Reynolds numbers by varying the tunnel supply pressure and temperature, thus providing data for naturally turbulent boundary layers. The experimental results were compared with existing theories which predict convective Stanton number or skin-friction coefficients. These comparisons indicate that the heat-transfer data are best predicted by the Spalding-Chi law and the skin friction by the Sommer-Short reference temperature method. The experimental Reynolds analogy factor is adequately predicted by Colburn's incompressible correlation for wall-to-stagnation temperature ratios above about 0.5. However, for lower wall temperature ratios, the experimental Reynolds analogy factor decreases with decreased temperature ratios in a manner which has not been previously reported. (Author).

Download or read book A General Review of Concepts for Reducing Skin Friction Including Recommendations for Future Studies written by Michael C. Fischer and published by . This book was released on 1974 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer and Skin Friction for Turbulent Boundary Layers on Heated Or Cooled Surfaces at High Speeds written by Langley Aeronautical Laboratory and published by Hassell Street Press. This book was released on 2021-09-09 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. To ensure a quality reading experience, this work has been proofread and republished using a format that seamlessly blends the original graphical elements with text in an easy-to-read typeface. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.

Download or read book Summary and Correlation of Skin friction and Heat transfer Data for a Hypersonic Turbulent Boundary Layer on Simple Shapes written by and published by . This book was released on 1965 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Skin Friction and Heat Transfer in Turbulent Boundary Layers Subjected to Small scale Free stream Turbulence written by Michael Joseph Barrett and published by . This book was released on 1998 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer Mass Transfer and Friction in Turbulent Boundary Layers written by Samson Semenovich Kutateladze and published by Core/Mechanical. This book was released on 1990 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reflects the growing practical applications for methods of computing the turbulent boundary layer based on relative limiting friction and heat exchange laws. Highlighted are conditions existing under two-phase flow and novel applications of injection critical parameters.

Download or read book Experimental study of the compressible turbulent boundary layer skin friction and heat transfer in the fully rough regime written by Howell Wesley Mann and published by . This book was released on 1968 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissociation Effects Upon Compressible Turbulent Boundary Layer Skin Friction and Heat Transfer written by William H. Dorrance and published by . This book was released on 1960 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Calculation Method for the Skin Friction and Heat Transfer of a Turbulent Boundary Layer with Variable Free Stream Velocity written by S. Levy and published by . This book was released on 1951 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineering Prediction of Turbulent Skin Friction and Heat Transfer in High speed Flow written by Aubrey M. Cary and published by . This book was released on 1974 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Control of Turbulent Boundary Layers by Uniform Injection and Suction of Fluid written by Julius C. Rotta and published by . This book was released on 1970 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent boundary layer control by injection is report as an effective means to reduce skin friction and heat transfer. Suction may be applied when boundary layer separation is to be prevented.

Download or read book The Influence of Surface Injection on Heat Transfer and Skin Friction Associated with the High speed Turbulent Boundary Layer written by Morris W. Rubesin and published by . This book was released on 1956 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Calculation of Turbulent Boundary Layers with Heat Transfer and Pressure Gradient Utilizing a Compressibility Transformation Part 2 Constant Property Turbulent Boundary Layer Flow with Simultaneous Mass Transfer and Pressure Gradient written by and published by . This book was released on 1972 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Local Coefficients of Skin Friction and Heat Transfer for Turbulent Boundary Layers on Two dimensional Diffusers written by J. N. Hool and published by . This book was released on 1954 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: