A Unified View Of Global Instabilities Of Compressible Flow Over Open Cavities
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| Total Pages | : 7 |
| Release | : 2005 |
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We report progress in our ongoing effort to compute and understand the three-dimensional instabilities (resonance) of open cavity flows from incompressible to supersonic speeds. In particular, our work is aimed at regimes where significant interactions occur between the shear layer spanning the cavity and the recirculating flow within the cavity, as encountered in many experiments and numerical simulations reported in the literature. Complementary methodologies for extracting information about global instabilities (including their receptivity and optimal control) of two- and three-dimensional cavity flows have been developed. We present here some sample calculations that show that for a low Mach number cavity with a length-to-depth ratio of two, the two-dimensional steady flow is unstable to three-dimensional (spanwise homogeneous) disturbances that consist of spanwise modulation of the recirculating vortex interior to the cavity. The oscillations are unstable over a narrow band of spanwise wavelengths comparable to the cavity depth. They are oscillatory in time, but with a very slow frequency that is about ten times slower than the incipient two-dimensional Rossiter instability. Instability seems to be related to cellular patterns observed in surface streamline patterns on cavity bottoms in some previous experiments.
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| Total Pages | : 56 |
| Release | : 2006 |
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This report results from a contract tasking Nu-modeling Inc, as follows: The contractor will investigate the global linear instability of three- dimensional flow over an open cavity to develop a unified framework for understanding and controlling cavity-driven instabilities, Specifically the contractor will: (1) Perform global instability analyses of the flow field in two-dimensional open cavities: (2) Investigate linear and nonlinear interaction of the modes using simplified models and compare with DNS results, and assess the limits of usefulness of existing empirical prediction models, (3) Perform two-dimensional DNS and global instability analysis of full-bay open-cavity models, Compare results with DNS and/or experiment, and propose adjustments of the empirical models, (4) Perform three-dimensional DNS in empty open cavities and classify global instabilities as functions of flow and geometric parameters, (5) Propose theoretically founded flow-control strategies for realistic geometries and flow conditions.
| Author | : V. Theofilis |
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| Release | : 2003 |
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| Author | : S. G. Kelly |
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| Total Pages | : 44 |
| Release | : 1984 |
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The mathematical modelling of the two dimensional compressible for over an open rectangular cavity is considered. The flow field is divided into three regions: (1) the two-dimensional compressible flow outside the cavity which is governed by a convective wave equation; (2) the two dimensional flow inside the cavity for which the mean flow is neglected and thus is governed by the wave equation; and (3) the shear layer spanning the cavity which is the major focus of the investigation. the work of Tam and Block is followed and a method for determining the discrete frequencies of shear layer oscillation is determined including shear layer thickness effects and assuming that the shear layer grows downstream. a line source placed at the trailing edge is used to model the trailing edge interaction process and the analysis of a shear layer excited by a reflected wave of arbitrary frequency is considered. Since the mean flow in the shear layer is nonuniform, standard stability procedures do not work. The nonparallel effects are assumed to be weak. The method of multiple scales is used to analyze the nonparallel stability of the shear layer. The stability characteristics of the shear layer are used in an equation developed by Tam and Block to predict discrete oscillation frequencies. The numerical methods for solving the equations are discussed. Originator-supplied keywords include: Open cavity flows; Nonparallel stability; and Multiple scales.
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| Total Pages | : 980 |
| Release | : 1998 |
| Genre | : Aeronautics |
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| Author | : American Institute of Aeronautics and Astronautics |
| Publisher | : |
| Total Pages | : 1380 |
| Release | : 2006 |
| Genre | : Aeronautics |
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| Author | : Alexander Gelfgat |
| Publisher | : Springer |
| Total Pages | : 524 |
| Release | : 2018-07-06 |
| Genre | : Technology & Engineering |
| ISBN | : 3319914944 |
Instabilities of fluid flows and the associated transitions between different possible flow states provide a fascinating set of problems that have attracted researchers for over a hundred years. This book addresses state-of-the-art developments in numerical techniques for computational modelling of fluid instabilities and related bifurcation structures, as well as providing comprehensive reviews of recently solved challenging problems in the field.
| Author | : Samui, Pijush |
| Publisher | : IGI Global |
| Total Pages | : 544 |
| Release | : 2016-08-12 |
| Genre | : Technology & Engineering |
| ISBN | : 152250589X |
The development of new and effective analytical and numerical models is essential to understanding the performance of a variety of structures. As computational methods continue to advance, so too do their applications in structural performance modeling and analysis. Modeling and Simulation Techniques in Structural Engineering presents emerging research on computational techniques and applications within the field of structural engineering. This timely publication features practical applications as well as new research insights and is ideally designed for use by engineers, IT professionals, researchers, and graduate-level students.
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| Total Pages | : 400 |
| Release | : 1948 |
| Genre | : Mechanics, Applied |
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| Author | : François Charru |
| Publisher | : Cambridge University Press |
| Total Pages | : 411 |
| Release | : 2011-06-30 |
| Genre | : Science |
| ISBN | : 1139500546 |
The instability of fluid flows is a key topic in classical fluid mechanics because it has huge repercussions for applied disciplines such as chemical engineering, hydraulics, aeronautics, and geophysics. This modern introduction is written for any student, researcher, or practitioner working in the area, for whom an understanding of hydrodynamic instabilities is essential. Based on a decade's experience of teaching postgraduate students in fluid dynamics, this book brings the subject to life by emphasizing the physical mechanisms involved. The theory of dynamical systems provides the basic structure of the exposition, together with asymptotic methods. Wherever possible, Charru discusses the phenomena in terms of characteristic scales and dimensional analysis. The book includes numerous experimental studies, with references to videos and multimedia material, as well as over 150 exercises which introduce the reader to new problems.
