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Numerical studies of unsteady laminar boundary-layer separation over impulsively-started moving objects.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Numerical studies of unsteady laminar boundary-layer separation over impulsively-started moving objects./
作者:	Wu, Tzuyin.
面頁冊數:	1 online resource (258 pages)
附註:	Source: Dissertations Abstracts International, Volume: 53-07, Section: B.
Contained By:	Dissertations Abstracts International53-07B.
標題:	Mechanical engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9204086click for full text (PQDT)
ISBN:	9798492749521

Numerical studies of unsteady laminar boundary-layer separation over impulsively-started moving objects.
Wu, Tzuyin.

Numerical studies of unsteady laminar boundary-layer separation over impulsively-started moving objects. - 1 online resource (258 pages)

Source: Dissertations Abstracts International, Volume: 53-07, Section: B.

Thesis (Ph.D.)--Cornell University, 1991.

Includes bibliographical references

To understand unsteady separated flows over a maneuvering body requires an analysis of the Navier-Stokes equations in a set of body-fixed coordinates. Effects of the extra apparent body forces in various combinations are yet to be systematically explored. The boundary-layer equations in body-fixed coordinates, however, retain the usual form except for the Coriolis term arising from the body rotation. In the two-dimensional case, the Coriolis term is absent. Computed results of the initiation of unsteady separation, according to the Lagrangian criterion, over a circular cylinder impulsively started into several variable motions, including linear acceleration/deceleration as well as rotation about different pivot locations, are presented and discussed. Effects of sudden change of the cylinder motion are examined through visualizing the evolving singular deformation of the influenced 'fluid packet' away from the wall. Calculations of general unsteady three-dimensional boundary-layer flows are fraught with difficulties. Resolution of the singular behavior at separation is a delicate problem. The task is further complicated by the geometric singularities associated with body-oriented coordinate systems and the inherent motion of the stagnation point. A numerical scheme is proposed to sidestep these difficulties. As the first stage of development, the simpler problem of the boundary layer over a suddenly started prolate spheroid at both large and small incidences is calculated. The formation of a three-dimensional separation is then investigated. Details of displacement-velocity distributions and streamline patterns are examined and discussed. From a physical viewpoint, separation shows up as an abrupt eruption of a certain 'fluid packet' that becomes deformed into one having zero thickness in a direction parallel to the surface. In the present case, the computed results suggest that this eruption, identified as a rapidly growing local thickness of the boundary layer, appears to occur first at a point in the symmetry plane and then spread in the crosswise direction. Figuratively, the boundary layer would develop a crescent shaped mountain-ridge thrusting itself into the main stream. Present findings about the features of separation are consistent with those deduced from the Lagrangian formulation.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798492749521Subjects--Topical Terms:

649730
Mechanical engineering.
Subjects--Index Terms:

moving objectsIndex Terms--Genre/Form:

542853
Electronic books.

Numerical studies of unsteady laminar boundary-layer separation over impulsively-started moving objects.
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504 $a Includes bibliographical references
520 $a To understand unsteady separated flows over a maneuvering body requires an analysis of the Navier-Stokes equations in a set of body-fixed coordinates. Effects of the extra apparent body forces in various combinations are yet to be systematically explored. The boundary-layer equations in body-fixed coordinates, however, retain the usual form except for the Coriolis term arising from the body rotation. In the two-dimensional case, the Coriolis term is absent. Computed results of the initiation of unsteady separation, according to the Lagrangian criterion, over a circular cylinder impulsively started into several variable motions, including linear acceleration/deceleration as well as rotation about different pivot locations, are presented and discussed. Effects of sudden change of the cylinder motion are examined through visualizing the evolving singular deformation of the influenced 'fluid packet' away from the wall. Calculations of general unsteady three-dimensional boundary-layer flows are fraught with difficulties. Resolution of the singular behavior at separation is a delicate problem. The task is further complicated by the geometric singularities associated with body-oriented coordinate systems and the inherent motion of the stagnation point. A numerical scheme is proposed to sidestep these difficulties. As the first stage of development, the simpler problem of the boundary layer over a suddenly started prolate spheroid at both large and small incidences is calculated. The formation of a three-dimensional separation is then investigated. Details of displacement-velocity distributions and streamline patterns are examined and discussed. From a physical viewpoint, separation shows up as an abrupt eruption of a certain 'fluid packet' that becomes deformed into one having zero thickness in a direction parallel to the surface. In the present case, the computed results suggest that this eruption, identified as a rapidly growing local thickness of the boundary layer, appears to occur first at a point in the symmetry plane and then spread in the crosswise direction. Figuratively, the boundary layer would develop a crescent shaped mountain-ridge thrusting itself into the main stream. Present findings about the features of separation are consistent with those deduced from the Lagrangian formulation.
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