Non-parallel Stability of Compressible Boundary Layers PDF Download
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Author: Chau-Lyan Chang
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Languages : en
Pages :
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Author: Chau-Lyan Chang
Publisher:
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Category :
Languages : en
Pages :
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Author: Sean H. Hu
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Category :
Languages : en
Pages :
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Author: Nabil M. El-Hady
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Category : Fluid mechanics
Languages : en
Pages : 44
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Book Description
Author: Nabil M. El- Hady
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
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Book Description
Author: J. S. B. Gajjar
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Author: G. L. Goglia
Publisher:
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Category : Fluid mechanics
Languages : en
Pages : 72
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Author: Eli Reshotko
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Category : Aerodynamics
Languages : en
Pages : 48
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Author: S.P. Lin
Publisher: Springer Science & Business Media
ISBN: 3642850847
Category : Science
Languages : en
Pages : 479
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Book Description
The IUTAM Symposium on Nonlinear Instability of Nonparallel Flows was held at Clarkson University, Potsdam, NY 13699-5725, USA from 26 to 31 July 1993. It consisted of 9 general speeches, 35 lectures and 15 poster-seminar presentations. The papers were grouped in fairly focused sessions on boundary layers, shear flows, vortices, wakes, nonlinear waves and jets. The symposium was fol lowed by a workshop in which the subject matter discussed was sum marized and some further work for future investigation was recom mended. The highlights of the workshop will be reported elsewhere. In this book many of the papers that describe the ideas presented at the symposium are collected to provide a reference for researchers in charting the future course of their studies in the area of nonlinear instability of nonparallel flows. The papers in this book are grouped under the following headings: • Boundary layers and shear flows • Compressibility and thermal effects • Vortices and wakes • Nonlinear waves and jets In the lead paper ofthis book M. E. Goldstein describes an asymp totic theory of nonlinear interaction between two spatially growing oblique waves on nonparallel boundary and free-shear layers. The wave interaction originates from the nonlinear critical layer and is responsive to weakly nonparallel effects. The theory results in a sys tem of integral differential equations which appear to be relevant near the upper branch of the neutral curve.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722458843
Category :
Languages : en
Pages : 46
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Numerical methods for the compressible boundary-layer equations are facilitated by transformation from the physical (x, y) plane to a computational (xi, eta) plane in which the evolution of the flow is 'slow' in the time-like xi direction. The commonly used Levy-Lees transformation results in a computationally well-behaved problem for a wide class of non-similar boundary-layer flows, but it complicates interpretation of the solution in physical space. Specifically, the transformation is inherently nonlinear, and the physical wall-normal velocity is transformed out of the problem and is not readily recovered. In light of recent research which shows mean-flow non-parallelism to significantly influence the stability of high-speed compressible flows, the contribution of the wall-normal velocity in the analysis of stability should not be routinely neglected. Conventional methods extract the wall-normal velocity in physical space from the continuity equation, using finite-difference techniques and interpolation procedures. The present spectrally-accurate method extracts the wall-normal velocity directly from the transformation itself, without interpolation, leaving the continuity equation free as a check on the quality of the solution. The present method for recovering wall-normal velocity, when used in conjunction with a highly-accurate spectral collocation method for solving the compressible boundary-layer equations, results in a discrete solution which is extraordinarily smooth and accurate, and which satisfies the continuity equation nearly to machine precision. These qualities make the method well suited to the computation of the non-parallel mean flows needed by spatial direct numerical simulations (DNS) and parabolized stability equation (PSE) approaches to the analysis of stability. Pruett, C. David Unspecified Center NAS1-18599; RTOP 505-59-53-02.
Author: Marie F.C. Denison
Publisher:
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Category :
Languages : en
Pages :
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The reduction of drag and aerodynamic heating caused by boundary layer transition is of central interest for the development of hypersonic vehicles. Receptivity to flow perturbation in the form of Tollmien-Schlichting (TS) wave growth often determines the first stage of the transition process, which can be delayed by depositing specific excitations into the boundary layer. Weakly ionized Dielectric Barrier Discharge (DBD) actuators are being investigated as possible sources of such excitations, but little is known today about their interaction with high-speed flows. In this framework, the first part of the thesis is dedicated to a receptivity study of laminar compressible boundary layers over a flat plate by linear stability analysis following an adjoint operator formulation, under DBD representative excitations assumed independent of flow conditions. The second part of the work concentrates on the development of a coupled plasma-Navier and Stokes solver targeted at the study of supersonic flow and compressibility effects on DBD forcing and non-parallel receptivity.The linear receptivity study of quasi-parallel compressible flows reveals several interesting features such as a significant shift of the region of maximum receptivity deeper into the flow at high Mach number and strong wave amplitude reduction compared to incompressible flows. The response to DBD relevant excitation distributions and to variations of the base flow conditions and system length scales follows these trends. Observed absolute amplitude changes and relative sensitivity modifications between source types are related to the evolution of the offset between forcing peak profile and relevant adjoint mode maximum. The analysis highlights the crucial importance of designing and placing the actuator in a way that matches its force field to the position of maximum boundary layer receptivity for the specific flow conditions of interest. In order to address the broad time and length scale spectrum inherent to the compressible flow-plasma problem, a solver has been developed using a novel Adaptive Mesh Refinement (AMR) algorithm based on the Chombo design for the solution of partial differential equations. Its embedded boundary formalism is utilized to solve the electrostatic potential in the complete domain including the DBD dielectric layer. The program allows accounting for non-equilibrium electron energization and resulting effect on transport and chemical reactions, with air or helium chemistry parametrization. Preliminary direct discharge test cases are reported for the latter.
