Author: Sidney E. Fuchs
Publisher:
ISBN:
Category : Finite differences
Languages : en
Pages : 268

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Book Description
Abstract.

Author: Alidad Amirfazli
Publisher:
ISBN:
Category : Cylinders
Languages : en
Pages : 0

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Book Description
A numerical study was made of imploding shock waves. The objective of the present paper is to clarify the propagation and instability of the converging cylindrical and elliptical shock waves. In order to make the simulation, a second order explicit MacCormack type finite difference method was employed to solve the unsteady compressible Euler equations. At first, a one-dimensional simulation was preformed for converging cylindrical shock waves. The results were found to be in good agreement with the Chester, Chisnell and whitham relation. Also, the numerical results were in good agreement with other published 1-D numerical simulations (e.g. method of characteristic). A two-dimensional simulation was also developed for initially perturbed implosions. The governing fluid dynamics equations have been solved in polar coordinates. The 2-D scheme is an extension to the 1-D case, using the operator splitting, where the multi-dimensional solution is evolved from a factored sequence of one dimensional operators. From the two-dimensional study of converging cylindrical shocks, it has been concluded that although the shock has been perturbed initially in the azimuthal direction, it has a tendency to keep its continuous shock front curvature until it gets close to the centre. Eventually, at the centre a break down in the shock front is inevitable. Finally, for the elliptical shock the perturbation parameter ($\xi$) was found to vary with shock travel in a complex manner that cannot be represented by a simple power law. This finding is in good agreement with recent experimental results.

Author: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1461305993
Category : Science
Languages : en
Pages : 411

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Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 32 (thesis year 1987) a total of 12,483 theses titles from 22 Canadian and 176 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 32 reports theses submitted in 1987, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.

Author: Ismaïl Ben Hassan Saïdi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Situations where an incident shock wave impinges upon a boundary layer are common in the aeronautical and spatial industries. Under certain circumstances (High Mach number, large shock angle...), the interaction between an incident shock wave and a boundary layer may create an unsteady separation bubble. This bubble, as well as the subsequent reflected shock wave, are known to oscillate in a low-frequency streamwise motion. This phenomenon, called the unsteadiness of the shock wave boundary layer interaction (SWBLI), subjects structures to oscillating loads that can lead to damages for the solid structure integrity.The aim of the present work is the unsteady numerical simulation of (SWBLI) in order to contribute to a better understanding of the SWBLI unsteadiness and the physical mechanism causing these low frequency oscillations of the interaction zone.To perform this study, an original numerical approach is used. The one step Finite Volume approach relies on the discretization of the convective fluxes of the Navier Stokes equations using the OSMP scheme developed up to the 7-th order both in space and time, the viscous fluxes being discretized using a standard centered Finite-Difference scheme. A Monotonicity-Preserving (MP) constraint is employed as a shock capturing procedure. The validation of this approach demonstrates the correct accuracy of the OSMP scheme to predict turbulent features and the great efficiency of the MP procedure to capture discontinuities without spoiling the solution and with an almost negligible additional cost. It is also shown that the use of the highest order tested of the OSMP scheme is relevant in term of simulation time and accuracy compromise. Moreover, an order of accuracy higher than 2-nd order for approximating the diffusive fluxes seems to have a negligible influence on the solution for such relatively high Reynolds numbers.By simulating the 3D unsteady interaction between a laminar boundary layer and an incident shock wave, we suppress the suspected influence of the large turbulent structures of the boundary layer on the SWBLI unsteadiness, the only remaining suspected cause of unsteadiness being the dynamics of the separation bubble. Results show that only the reattachment point oscillates at low frequencies characteristic of the breathing of the separation bubble. The separation point of the recirculation bubble and the foot of the reflected shock wave have a fixed location along the flat plate with respect to time. It shows that, in this configuration, the SWBLI unsteadiness is not observed.In order to reproduce and analyse the SWBLI unsteadiness, the simulation of a shock wave turbulent boundary layer interaction (SWTBLI) is performed. A Synthetic Eddy Method (SEM), adapted to compressible flows, has been developed and used at the inlet of the simulation domain for initiating the turbulent boundary layer without prohibitive additional computational costs. Analyses of the results are performed using, among others, the snapshot Proper Orthogonal Decomposition (POD) technique. For this simulation, the SWBLI unsteadiness has been observed. Results suggest that the dominant flapping mode of the recirculation bubble occurs at medium frequency. These cycles of successive enlargement and shrinkage of the separated zone are shown to be irregular in time, the maximum size of the recirculation bubble being submitted to discrepancies between successive cycles. This behaviour of the separation bubble is responsible for a low frequency temporal modulation of the amplitude of the separation and reattachment point motions and thus for the low frequency breathing of the separation bubble. These results tend to suggest that the SWBLI unsteadiness is related to this low frequency dynamics of the recirculation bubble; the oscillations of the reflected shocks foot being in phase with the motion of the separation point.

Author: Michael Shearer
Publisher: SIAM
ISBN: 9780898712834
Category : Science
Languages : en
Pages : 272

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Book Description
One strongly represented theme is the power of ideas from dynamical systems that are being adapted and developed in the context of shock waves.

Author: Christopher E. Glass
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 28

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Book Description
CFD numerical simulations of low-density shock-wave interactions for an incident shock impinging on a cylinder have been performed. Flow-field density gradient and surface pressure and heating define the type of interference pattern and corresponding perturbations. The maximum pressure and heat transfer level and location of various interaction types are presented. A time-accurate solution of the Type IV interference is employed to demonstrate the establishment and the steadiness of the low-density flow interaction.

Author: Seán Prunty
Publisher: Springer
ISBN: 9783030636081
Category : Science
Languages : en
Pages : 344

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Book Description
This book provides an elementary introduction to one-dimensional fluid flow problems involving shock waves in air. The differential equations of fluid flow are approximated by finite difference equations and these in turn are numerically integrated in a stepwise manner, with artificial viscosity introduced into the numerical calculations in order to deal with shocks. This treatment of the subject is focused on the finite-difference approach to solve the coupled differential equations of fluid flow and presents the results arising from the numerical solution using Mathcad programming. Both plane and spherical shock waves are discussed with particular emphasis on very strong explosive shocks in air. This expanded second edition features substantial new material on sound wave parameters, Riemann's method for numerical integration of the equations of motion, approximate analytical expressions for weak shock waves, short duration piston motion, numerical results for shock wave interactions, and new appendices on the piston withdrawal problem and numerical results for a closed shock tube. This text will appeal to students, researchers, and professionals in shock wave research and related fields. Students in particular will appreciate the benefits of numerical methods in fluid mechanics and the level of presentation.

Author: Richard W. Barnwell
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 44

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Book Description
The finite-difference method which Peter D. Lax developed for treating unsteady inviscid flow fields is used to study the transient flow in the shock layer of a sphere that has been struck by a normal shock wave. Transient flow of this sort is encountered when a shock tube is used as a supersonic wind tunnel. Time histories of the shock detachment distance and the stagnation-point pressure and tangential velocity gradient are presented for ranges of the incident-shock Mach number and the perfect-gas specific-heat ratio. These results show that the stagnation-point pressure approaches the steady value much more rapidly than the shock detachment distance. In general, the stagnation-point pressure but more rapidly than the shock detachment distance. As the specific-heat ratio is decreased and the incident-shock Mach number is increased, the variation of the velocity gradient with respect to the shock detachment distance becomes more nearly linear.

Author: Yoshisuke Nakano
Publisher:
ISBN:
Category : Blast effect
Languages : en
Pages : 29

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Book Description
A finite difference method for predicting the effect of shock waves on a circular cylindrical cavity in elastic-plastic media was studied. A two-dimensional Lagrangian code was found quite satisfactory. Attenuation of the shock waves through the cavity and the deformation of the cavity wall were discussed. (Author).

Author: Raymond Brun
Publisher: Springer Science & Business Media
ISBN: 3642795323
Category : Science
Languages : en
Pages : 508

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Book Description
Recently, there have been significant advances in the fields of high-enthalpy hypersonic flows, high-temperature gas physics, and chemistry shock propagation in various media, industrial and medical applications of shock waves, and shock-tube technology. This series contains all the papers and lectures of the 19th International Symposium on Shock Waves held in Marseille in 1993. They are published in four topical volumes, each containing papers on related topics, and preceded by an overview written by a leading international expert. The volumes may be purchased independently.