Flow-visualization of Three-dimensional Boundary-layer Separation on Bodies of Revolution at Incidence PDF Download

Author: Taeyoung Han
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 86

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Book Description
Surface streamline patterns on three bodies of revolution, namely a spheroid, a low-drag body and a hemisphere-hemispheroid combination body, have been examined at several angles of attack. Most of the tests were performed at low Reynolds numbers in a hydraulic flume using colored dye to make the surface flow visible. A limited number of experiments was also carried out in a wind tunnel, using wool tufts, to study the influence of Reynolds number and turbulent separation. The study has verified some of the important qualitative features of three-dimensional separation criteria proposed earlier by Maskell, Lighthill, Wang and others. The observed locations of laminar separation lines on a spheroid at various incidences have been compared with the numerical boundary-layer solutions of Wang, and it is suggested that the quantitative differences may be attributed to the significant viscous-inviscid interaction, especially at large incidences. (Author).

Author: V. C. Patel
Publisher:
ISBN:
Category :
Languages : en
Pages : 13

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Book Description
This report summarizes the objectives and accomplishments of an experimental and theoretical investigation of the boundary layer development on bodies of revolution at incidence. The results of the flow visualization studies in laminar flow, detailed measurements in a turbulent boundary layer, and calculations of laminar as well as turbulent boundary layers using two different numerical schemes and turbulence models are reviewed to emphasize the important characteristics of separation in three dimensions.

Author: H. U. Meier
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

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Book Description
Detailed measurements in three-dimensional boundary layers and separated flow fields, developing on a prolate spheroid, are presented. The discussion is concentrated on the possible topological structure of separation patterns resulting from laminar or turbulent boundary layer flows. A hypothesis about the transition from an unsteady two-dimensional axisymmetric flow separation into a steady three-dimensional vortex flow is established. (Author).

Author: Jean Délery
Publisher: John Wiley & Sons
ISBN: 1118579887
Category : Science
Languages : en
Pages : 181

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Book Description
This book develops concepts and a methodology for a rational description of the organization of three-dimensional flows considering, in particular, the case where the flow is the place of separations. The descriptive analysis based on the critical point theory of Poincaré develops conventional but rather unfamiliar considerations from aerodynamicists, who face the understanding of complex flows including multiple separation lines and vortices. These problems concern industrial sectors where aerodynamics plays a key role, such as aerospace, ground vehicles, buildings, etc. Contents 1. Skin Friction Lines Pattern and Critical Points. 2. Separation Streamsurfaces and Vortex Structures. 3. Separated Flow on a Body. 4. Vortex Wake of Wings and Slender Bodies. 5. Separation Induced by an Obstacle or a Blunt Body. 6. Reconsideration of the Two-Dimensional Separation. 7. Concluding Remarks. About the Authors Jean Délery is a Supaero (French National Higher School of Aeronautics and Space) engineer who has worked at Onera (French national aerospace research center) since 1964. He has participated in several major French and European aerospace programs, is the author of many scientific publications, and has occupied various teaching positions particularly at Supaero, the University of Versailles-Saint-Quentin, Ecole polytechnique in France and “La Sapienza” University in Rome, Italy. He is currently emeritus adviser at Onera.

Author: Tuncer Cebeci
Publisher:
ISBN:
Category :
Languages : en
Pages : 66

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Book Description
An investigation is carried out into the structure of the laminar boundary layer originating from the forward stagnation point of a prolate spheroid at incidence in a uniform stream, assuming that the external velocity distribution is given by attached potential theory. The principal new results of the study are: (1) A new transformation of the body coordinates is devised which facilitates the computation of the solution near the nose, (2) Two variations of the standard box method of solving the equations are devised to enable solutions to be computed in regions of cross-flow reversal, (3) Whereas in two dimensional flows the effect of the boundary layer approaching separation on the external flow may be represented by a blowing velocity, in the present study we find that this is only true near the windward line of symmetry, (4) The boundary layer over the whole of the spheroid cannot be computed in an integration from the forward stagnation point. (5) For alpha> or = 15 deg the accessible region on the leeward side of the ok is largely determined by the external streamline through the ok.

Author: V. C. Patel
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 32

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Book Description
Three-dimensional thin boundary-layer equations for laminar and turbulent flows are solved by two different numerical schemes. The methods are applied to the flow over bodies of revolution at incidence and the results are compared with the available experimental data in order to study the range of validity of the classical boundary-layer approximations in regions of increasing circumferential gradients and flow reversal associated with the early stages of a free-vortex type of separation. Comparison with the DFVLR 6:1 spheroid data of Meier et al and the 4:1 combination-body data of Ramaprian, Patel and Choi indicate that the methods perform well in regions where the boundary layer remains thin but the predictions deteriorate as the boundary layer thickens. The results point out the need for the development of methods of handle thick boundary layers and viscous-inviscid interactions. (Author).

Author: V. C. Patel
Publisher:
ISBN:
Category :
Languages : en
Pages : 29

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Book Description
An experimental and theoretical study of three-dimensional boundary layers on bodies of revolution at incidence was conducted during the period May 1980-July 1983. This final report summarizes the technical accomplishments. Reference is made to previous reports and papers resulting from the study and some recent experimental results on the boundary layer in the plane of symmetry and the vortex formation region are presented. One of the primary objectives of this study was to develop instrumentation for the measurement of the mean flow and the Reynolds stresses in three-dimensional turbulent boundary layers, and to use these to supplement the mean-flow measurements made earlier by Ramaprian, Patel and Choi on the combination body at an incidence of 15 degrees.

Author: Walter B. Sturek
Publisher:
ISBN:
Category : Body of revolution
Languages : en
Pages : 38

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Book Description
Experimental measurements of the three dimensional boundary layer on a yawed, spinning tangent-ogive-cylinder model in supersonic flow are reported. The measurements were made using a flattened total head probe at one axial station near the base of the model for 10 azimuthal stations about the circumference. The test conditions were: M = 3, angle of attack = 4 deg, omega = 0 and 10,000 RPM. The trends observed in comparing measurements with and without the model spinning were: (1) the boundary layer is more thick and less full where surface spin opposes the crossflow velocity; and (2) the boundary layer is less thick and more full where surface spin is in the same direction as the crossflow velocity. (Author).

Author: Raymond Sedney
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 64

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Book Description
The subject is investigated with flow visualization techniques; the turbulent boundary layer on the wall of a continuous supersonic wind tunnel is used. Sizeable separated flow regions can be studied since the wall width is 38cm and the boundary layer is typically 2.5cm thick. The large scale of the experiment is required to resolve the fine details of the flow structure. The flow visualization techniques are discussed. The structure of the separated flow upstream of the obstacle is seen to change with relatively small changes in Reynolds number R; the number of vortices varies from 6 to 4 to 2 as R changes. Data are presented for large and small protuberances, but the latter are emphasized.

Author: H. U. Meier
Publisher:
ISBN:
Category :
Languages : en
Pages : 18

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Book Description
Detailed measurements in three-dimensional boundary layers and separated flow fields, developing on a prolate spheroid and flow visualizations are presented. The discussion is concentrated on the possible topological structure of separation patterns resulting from laminar on turbulent boundary layer flows at different Reynolds numbers. (Author).