Review of the Effect of Distributed Surface Roughness on Boundary-layer Transition

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ISBN 13 :
Total Pages : 13 pages
Book Rating : 4.:/5 (177 download)

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Book Synopsis Review of the Effect of Distributed Surface Roughness on Boundary-layer Transition by : A. L. Braslow

Download or read book Review of the Effect of Distributed Surface Roughness on Boundary-layer Transition written by A. L. Braslow and published by . This book was released on 1960 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: A discussion is presented on the transition phenomena associated with distributed roughness, a correlation of three-dimensional roughness effects at both subsonic and supersonic speeds, and the effect of laminar boundary-layer stability as influenced by heat transfer, pressure gradients, and boundary-layer control on the sensitivity of laminar flow to distributed roughness. Results indicate that the transition-triggering mechanism of three-dimensionaltype surface roughness appears to be the same at supersonic and subsonic speeds. In either case, a Reynolds number based on the height of the roughness and the local flow conditions at the top of the roughness can be used to predict with reasonable accuracy the height of threedimensional roughness required to cause premature transition. Neither the three-dimensional roughness Reynolds number nor the lateral spread of turbulence behind the roughness is changed to any important extent by increasing the laminar boundary-layer stability to theoretically small disturbances. Therefore, for a given stream Mach number and Reynolds number, surface cooling, boundary-layer suction, or a favorable pressure gradient will, in the presence of three-dimensional roughness, promote rather than delay transition. (Author).

Initial Value Study of Effect of Distributed Roughness on Boundary Layer Transition

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ISBN 13 :
Total Pages : 118 pages
Book Rating : 4.:/5 (93 download)

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Book Synopsis Initial Value Study of Effect of Distributed Roughness on Boundary Layer Transition by : Taha Khalil Aldoss

Download or read book Initial Value Study of Effect of Distributed Roughness on Boundary Layer Transition written by Taha Khalil Aldoss and published by . This book was released on 1982 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

An Analytical Study of the Effects of Surface Roughness on Boundary-Layer Transition

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ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis An Analytical Study of the Effects of Surface Roughness on Boundary-Layer Transition by :

Download or read book An Analytical Study of the Effects of Surface Roughness on Boundary-Layer Transition written by and published by . This book was released on 1974 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analytical model has been developed to describe the manner in which distributed surface roughness affects transition. The model pictures the roughness as having two distinct effects: one, it introduces higher disturbance levels in the boundary layer; and two, it alters the mean velocity profile and, hence, the growth rate of the disturbances. The alteration of the mean velocity profile is described by means of a 'turbulent sublayer', which visualizes an enhanced momentum transfer in a narrow layer next to the surface. The corresponding change in the amplification of disturbances is then determined by means of linear stability theory, and is related to transition by an empirical transition criterion.

An Analytical Study of the Effect of Surface Roughness on Boundary-Layer Stability

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ISBN 13 :
Total Pages : 69 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis An Analytical Study of the Effect of Surface Roughness on Boundary-Layer Stability by : Charles L. Merkle

Download or read book An Analytical Study of the Effect of Surface Roughness on Boundary-Layer Stability written by Charles L. Merkle and published by . This book was released on 1977 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of surface roughness on the transition of a laminar boundary layer are basically two-fold: (1) it can distort the mean velocity and temperature profiles thus altering the stability characteristics of the layer and (2) it can induce additional disturbances to the boundary layer which may lead to an earlier transition. Only the first of these effects is considered in this report. Three different types of surface roughness are investigated here; distributed roughness, surface waviness, and a single two-dimensional bump. An analytical model which describes the effect of distributed roughness on the mean flow and its stability is described. This model is further validated by comparison with Achenbach's experimental results and is then applied to the flow about an underwater body in order to illustrate the effects of surface roughness in a more realistic situation. Surface irregularities can play a dominant role in determining the practical limit for the application of boundary-layer control techniques. The present distributed roughness model as incorporated into the TAPS code can provide a reasonable prediction of its effect in the presence of boundary-layer control techniques (shaping, heating, suction) on the transition location for an underwater vehicle.

NASA Technical Note

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ISBN 13 :
Total Pages : 1384 pages
Book Rating : 4.3/5 (91 download)

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Book Synopsis NASA Technical Note by :

Download or read book NASA Technical Note written by and published by . This book was released on 1971 with total page 1384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Effects of Specific Types of Surface Roughness on Boundary-layer Transition

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Publisher : Hassell Street Press
ISBN 13 : 9781015205086
Total Pages : 50 pages
Book Rating : 4.2/5 (5 download)

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Book Synopsis Effects of Specific Types of Surface Roughness on Boundary-layer Transition by : Langley Aeronautical Laboratory

Download or read book Effects of Specific Types of Surface Roughness on Boundary-layer Transition written by Langley Aeronautical Laboratory and published by Hassell Street Press. This book was released on 2021-09-10 with total page 50 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.

Effect of Distributed Three-dimensional Roughness and Surface Cooling on Boundary-layer Transition and Lateral Spread of Turbulence at Supersonic Speeds

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ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Effect of Distributed Three-dimensional Roughness and Surface Cooling on Boundary-layer Transition and Lateral Spread of Turbulence at Supersonic Speeds by : Albert L. Braslow

Download or read book Effect of Distributed Three-dimensional Roughness and Surface Cooling on Boundary-layer Transition and Lateral Spread of Turbulence at Supersonic Speeds written by Albert L. Braslow and published by . This book was released on 1959 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Effect of Large Distributed Roughness Near an Airfoil Leading Edge on Boundary-layer Development and Transition

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ISBN 13 :
Total Pages : 496 pages
Book Rating : 4.:/5 (348 download)

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Book Synopsis Effect of Large Distributed Roughness Near an Airfoil Leading Edge on Boundary-layer Development and Transition by : Michael Fort Kerho

Download or read book Effect of Large Distributed Roughness Near an Airfoil Leading Edge on Boundary-layer Development and Transition written by Michael Fort Kerho and published by . This book was released on 1995 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of the effects of large distributed roughness located near the leading-edge of an airfoil has been performed to determine the effect on boundary-layer development and transition. Boundary-layer measurements were carried out on a two-dimensional NACA 0012 airfoil with a 21" chord. The distributed roughness used was in the form of densely packed large hemispherical elements applied to the leading-edge region of the airfoil section. The size of the distributed roughness was greater than or on the order of the laminar boundary-layer thickness. The roughness used is of the type and density observed to occur during the initial glaze ice accretion process. Detailed boundary-layer measurements were obtained through the use of hot-wire anemometry at Reynolds numbers of 0.75 $times$ 10$sp6$, 1.25 $times$ 10$sp6$, and 2.25 $times$ 10$sp6$. These measurements included mean and fluctuating velocity, turbulence intensity, flowfield intermittency, frequency content, and associated integral parameters. Both the clean model and roughness induced transitional boundary-layers were studied in great detail. Results from this investigation have shown that the transitional boundary-layer induced by large distributed roughness is markedly different from the clean model Tollmein-Schlicting induced transition process. For the type of roughness used in this study no fully developed turbulent boundary-layers were observed to occur at the roughness location, even though roughness heights were substantially greater than empirically determined critical roughness heights required to cause transition. Instead, the large distributed roughness was observed to trigger a transitional boundary-layer at or very near the roughness location. This transitional boundary-layer required a substantial chordwise extent to obtain a fully developed turbulent state. Turbulence intensity levels in the roughness induced transitional region were observed to be relatively low as compared to the clean model transitional region. In general, the clean model transitional process was substantially more energetic than that observed for the roughness induced boundary-layer. A new method for determining the location and extent of the transitional region by integrating the profiles of intermittency is also presented.

An Analytical Study of the Effect of Surface Roughness on the Stability of a Heated Water Boundary Layer

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ISBN 13 :
Total Pages : 46 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis An Analytical Study of the Effect of Surface Roughness on the Stability of a Heated Water Boundary Layer by : Michael A. Kosecoff

Download or read book An Analytical Study of the Effect of Surface Roughness on the Stability of a Heated Water Boundary Layer written by Michael A. Kosecoff and published by . This book was released on 1976 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The onset of transition from laminar to turbulent flow in a high Reynolds number, water boundary layer was investigated with emphasis on predicting the global effects of distributed surface roughness on transition. The authors used the results of linear stability theory as an indicator of transition, but, this paper presents only comparisons of the stability results (not actual transition predictions). The effects of surface roughness on transition were induced by means of an existing phenomenological model for the effects of distributed roughness on the mean flow profiles. This model, originally developed for high Mach number, compressible boundary layers, was applied without change to the present incompressible, water boundary-layer environment, and identical values of the required empirical constants were used in both cases. One conclusion obtained from the numerical results is that the presence of favorable pressure gradients and/or surface heating make the boundary layer more susceptible to roughness, not only when compared in terms of the actual roughness height, but also when compared in terms of the roughness height to momentum thickness ratio. When the roughness is sufficiently large, its presence can change the effect of surface heat addition from a strongly stabilizing factor to a strongly destabilizing phenomena.

Roughness Effects on Boundary-layer Transition for Blunt-leading-edge Plates at Mach 6

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ISBN 13 :
Total Pages : 52 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Roughness Effects on Boundary-layer Transition for Blunt-leading-edge Plates at Mach 6 by : Paul F. Holloway

Download or read book Roughness Effects on Boundary-layer Transition for Blunt-leading-edge Plates at Mach 6 written by Paul F. Holloway and published by . This book was released on 1966 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

A Review of Factors Affecting Boundary-layer Transition

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ISBN 13 :
Total Pages : 36 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis A Review of Factors Affecting Boundary-layer Transition by : Albert L. Braslow

Download or read book A Review of Factors Affecting Boundary-layer Transition written by Albert L. Braslow and published by . This book was released on 1966 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

משחקידע

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (233 download)

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Book Synopsis משחקידע by :

Download or read book משחקידע written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

NASA Reference Publication

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ISBN 13 :
Total Pages : 984 pages
Book Rating : 4.:/5 (319 download)

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Book Synopsis NASA Reference Publication by :

Download or read book NASA Reference Publication written by and published by . This book was released on 1977 with total page 984 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds

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ISBN 13 :
Total Pages : 76 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds by : William A. Cassels

Download or read book Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds written by William A. Cassels and published by . This book was released on 1970 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boundary-layer transition by the sublimation and impact-pressure techniques and force tests have been performed on three Haack-Adams bodies of revolution of fineness ratios 7, 10, and 13 at zero angle of attack for free-stream Mach numbers of 2.00, 2.75, and 4.63 and a range of Reynolds numbers based on model length of 6 to 15 X 10(to the 6 power) with and without a roughness strip. The grit method of inducing turbulence was found to provide for a nearly complete turbulent flow over the models at the lower Mach numbers and higher Reynolds numbers considered in this study while the amount of trip drag was less than 8 percent of the model drag with transition fixed. A method of interpreting sublimation data was discussed and used and the results compared well with the impact-pressure results.

Effects of Specific Types of Surface Roughness on Boundary-layer Transition

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ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (11 download)

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Book Synopsis Effects of Specific Types of Surface Roughness on Boundary-layer Transition by : Laurence K. Loftin

Download or read book Effects of Specific Types of Surface Roughness on Boundary-layer Transition written by Laurence K. Loftin and published by . This book was released on 1946 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Distributed Roughness Receptivity in a Flat Plate Boundary Layer

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ISBN 13 :
Total Pages : pages
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Book Synopsis Distributed Roughness Receptivity in a Flat Plate Boundary Layer by : Matthew Scott Kuester

Download or read book Distributed Roughness Receptivity in a Flat Plate Boundary Layer written by Matthew Scott Kuester and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface roughness can affect boundary layer transition by acting as a receptivity mechanism for transient growth. Several experiments have investigated transient growth created by discrete roughness elements; however, very few experiments have studied transient growth initiated by distributed surface roughness. Some of the work in this field predicts a "shielding" effect, where smaller distributed roughness displaces the boundary layer away from the wall and shields larger roughness peaks from the incoming boundary layer. This dissertation describes an experiment specifically designed to study the shielding effect. Three roughness configurations, a deterministic distributed roughness patch, a slanted rectangle, and the combination of the two, were manufactured using rapid prototyping and installed flush with the wall in a flat plate boundary layer. The main objective was to compare the wakes of the discrete roughness and the combined roughness to examine if the distributed roughness shields the discrete roughness. Naphthalene flow visualization and hotwire anemometry were used to characterize the boundary layer in the wakes of the different roughness configurations. For roughness Reynolds numbers (Re[subscript k]) between 113 and 230, the distributed roughness initiated small amplitude disturbances that underwent transient growth. The discrete roughness element created a pair of high- and low-speed streaks in the boundary layer at a sub-critical Reynolds number (Re[subscript k]) = 151). At a higher Reynolds number (Re[subscript k]) = 220), the discrete element created a turbulent wedge 15 boundary layer thicknesses downstream. When the distributed roughness was added around the discrete roughness, the wake amplitude decreased at the sub-critical Reynolds number, and transition was delayed by two boundary layer thicknesses at the higher Reynolds number. The distributed roughness redirects energy from longer spanwise wavelength modes to shorter spanwise wavelength modes. The presence of the distributed roughness also decreased the growth rate of secondary instabilities in the roughness wake. This dissertation documents the first detailed measurements of transient growth over streamwise-extended distributed roughness and demonstrates that the shielding effect has the potential to delay roughness-induced transition. The results from this experiment lay the ground work for future studies of roughness receptivity and transient growth. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152606

An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer

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ISBN 13 :
Total Pages : 176 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer by :

Download or read book An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer written by and published by . This book was released on 1983 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: A previous study on the effect of surface roughness on the turbulent boundary layer, using a Fortran code, ITRACT, solved for the characteristics of a laminar, transitional and turbulent boundary layer on smooth surfaces. The present study investigates the influence of surface roughness on a compressible turbulent boundary layer and then extends the usefulness of ITRACT by including in it the optional capability of rough-surface boundary-layer calculations. Surface roughness was represented by distributed sources and sinks in the appropriate governing equations. The most important term is a sink term in the mean momentum equation, representing the form drag due to the roughness element. Governing boundary-layer equations for continuity, momentum, and energy were derived in a form to account for blockage effects due to roughness elements. The modified governing equations were then transformed using Probstein-Elliott and Levy-Lees transformations. The resulting equations, with appropriate boundary conditions, were solved by finite-difference techniques to determine the nondimensional velocity components and temperature at a finite number of nodes in the boundary-layer flow field.