On the Lagrangian Description of Unsteady Boundary Layer Separation
Author: Leon L. Van Dommelen
Publisher:
Published: 1989
Total Pages: 30
ISBN-13:
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Author: Leon L. Van Dommelen
Publisher:
Published: 1989
Total Pages: 30
ISBN-13:
DOWNLOAD EBOOKAuthor: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-07-09
Total Pages: 50
ISBN-13: 9781722455040
DOWNLOAD EBOOKAlthough unsteady, high-Reynolds number, laminar boundary layers have conventionally been studied in terms of Eulerian coordinates, a Lagrangian approach may have significant analytical and computational advantages. In Lagrangian coordinates the classical boundary layer equations decouple into a momentum equation for the motion parallel to the boundary, and a hyperbolic continuity equation (essentially a conserved Jacobian) for the motion normal to the boundary. The momentum equations, plus the energy equation if the flow is compressible, can be solved independently of the continuity equation. Unsteady separation occurs when the continuity equation becomes singular as a result of touching characteristics, the condition for which can be expressed in terms of the solution of the momentum equations. The solutions to the momentum and energy equations remain regular. Asymptotic structures for a number of unsteady 3-D separating flows follow and depend on the symmetry properties of the flow. In the absence of any symmetry, the singularity structure just prior to separation is found to be quasi 2-D with a displacement thickness in the form of a crescent shaped ridge. Physically the singularities can be understood in terms of the behavior of a fluid element inside the boundary layer which contracts in a direction parallel to the boundary and expands normal to it, thus forcing the fluid above it to be ejected from the boundary layer. Vandommelen, Leon L. and Cowley, Stephen J. Glenn Research Center NASA-SAA-C-99066-G; RTOP 505-62-21...
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-07-09
Total Pages: 26
ISBN-13: 9781722455163
DOWNLOAD EBOOKA theory to explain the initial stages of unsteady separation was proposed by Van Dommelen and Cowley (1989). This theory is verified for the separation process that occurs at the equatorial plane of a sphere or a spheroid which is impulsively spun around an axis of symmetry. A Lagrangian numerical scheme is developed which gives results in good agreement with Eulerian computations, but which is significantly more accurate. This increased accuracy, and a simpler structure to the solution, also allows verification of the Eulerian structure, including the presence of logarithmic terms. Further, while the Eulerian computations broke down at the first occurrence of separation, it is found that the Lagrangian computation can be continued. It is argued that this separated solution does provide useful insight into the further evolution of the separated flow. A remarkable conclusion is that an unseparated vorticity layer at the wall, a familiar feature in unsteady separation processes, disappears in finite time. Vandommelen, Leon L. Glenn Research Center ...
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-07-10
Total Pages: 70
ISBN-13: 9781722679392
DOWNLOAD EBOOKThe Lagrangian description of unsteady boundary layer separation is reviewed from both analytical and numerical perspectives. It is explained in simple terms how particle distortion gives rise to unsteady separation, and why a theory centered on Lagrangian coordinates provides the clearest description of this phenomenon. Some of the more recent results for unsteady three dimensional compressible separation are included. The different forms of separation that can arise from symmetries are emphasized. A possible description of separation is also included when the detaching vorticity layer exits the classical boundary layer region, but still remains much closer to the surface than a typical body-lengthscale. Cowley, Stephen J. and Vandommelen, Leon L. and Lam, Shui T. Unspecified Center...
Author: Stephen J. Cowley
Publisher:
Published: 1990
Total Pages: 72
ISBN-13:
DOWNLOAD EBOOKAuthor: Tzuyin Wu
Publisher:
Published: 1985
Total Pages: 202
ISBN-13:
DOWNLOAD EBOOKAuthor: Kazutoshi Tominaga
Publisher:
Published: 1992
Total Pages: 150
ISBN-13:
DOWNLOAD EBOOKAuthor: S. F. Shen
Publisher:
Published: 1986
Total Pages: 9
ISBN-13:
DOWNLOAD EBOOKThe central theme of research under this grant had been the study of phenomena of unsteady boundary layer separation, emphasizing but not restricted to the Lagrangian description.
Author: Leonard Louis Van Dommelen
Publisher:
Published: 1981
Total Pages: 516
ISBN-13:
DOWNLOAD EBOOKAuthor: Tzuyin Wu
Publisher:
Published: 1991
Total Pages: 504
ISBN-13:
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