Impact Of Roughness On Shock Wave Reflection Phenomena

The phenomenon of shock wave reflection was first reported by the distinguished philosopher Ernst Mach in 1878. Its study was then abandoned for a period of about 60 years until its investigation was initiated in the early 1940s by Professor John von Neumann and Professor Bleakney. Under their supervision, 15 years of intensive research related to various aspects of the reflection of shock waves in pseudo-steady flows were carried out. It was during this period that the four basic shock wave reflection configurations were discovered. Then, for a period of about 10 years from the mid 1950s until the mid 1960s, investigation of the reflection phenomenon of shock waves was kept on a low flame all over the world (e. g. Australia, Japan, Canada, U. S. A. , U. S. S. R. , etc. ) until Professor Bazhenova from the U. S. S. R. , Professor Irvine Glass from Canada, and Professor Roy Henderson from Australia re initiated the study of this and related phenomena. Under their scientific supervision and leadership, numerous findings related to this phenomenon were reported. Probably the most productive research group in the mid 1970s was that led by Professor Irvine Glass in the Institute of Aerospace Studies of the University of Toronto. In 1978, exactly 100 years after Ernst Mach first reported his discovery of the reflection phenomenon, I published my Ph. D. thesis in which, for the first time, analytical transition criteria between the various shock wave reflection configurations were established.

The aim of the present study was to study both experimentally and analytically the effect of the surface conditions on the shock reflection phenomenon. In general, the study was divided into two parts: (1) the reflection of a planar shock wave over rough surfaces, and (2) the reflection of a planar shock wave over a liquid surface. Keywords: Shock wave; Regular and Mach reflections; Boundary layer; Reflecting wedge; Pseudo-steady flow; Surface roughness; Von Neuman paradox.

An investigation has been conducted on a small-scale test layout in which direct observation of the shock-wave movement with time could be made in order to determine the effects of surface roughness on the characteristics of spherical shock waves. Data were obtained with 15-gram pentolite charges at four heights of burst, both for a smooth surface and for a surface completely covered with pyramid-shaped roughness elements. The observations calculated in determinations of shock peak over-pressure and Mach stem height as a function of distance for each test condition.

The purpose of these experiments conducted in the shock tube was to obtain qualitative information concerning the effect of various types and degrees of surface roughness on the diffraction of a shock wave about a two-dimensional model. A series of shadowgraphs was taken of the various blocks in the shock tube with incident over-pressure of 6 and 9 psi. Qualitative analysis of the data indicates that surface roughness reduces the velocity of the shock across the top near the rough surface and tends to hinder the developmemt of the front top vortex appreciably, but does not affect the development of the rear vortex to as great an extent.

This book presents a wealth of images of shock wave phenomena, gathered by the author over the past 40 years. Shadowgrams and interferograms of basic shock-dynamic topics such as reflection, diffraction, refraction, and focusing of shock waves in gases and liquids are sequentially displayed. Though the images themselves are self-explanatory, brief explanations of the experimental conditions are included, so as to facilitate analysis and numerical reproduction of the image data. In addition, the book presents interferometric observations of underwater shock wave/bubble interactions, and highlights the multifaceted applications of shock wave phenomena to medicine and industry. Given its scope, the book offers a unique resource for students and researchers who are interested in shock wave phenomena. However, the content has also been specifically prepared for the benefit of readers who are interested in gas dynamics and medical applications of shock waves, and are looking for reliable experimental images.

These proceedings of EXPLOMET 90, the International Conference on the Materials Effects of Shock-Wave and High-Strain-Rate Phenomena, held August 1990, in La Jolla, California, represent a global and up-to-date appraisal of this field. Contributions (more than 100) deal with high-strain-rate deforma

Measurements of peak overpressure and Mach stem height were made at four burst heights. Data were obtained with instrumentation capable of directly observing the variation of shock-wave movement with time. Good similarity of free-air shock peak overpressure with larger scale data was found to exist. The net effect of surface roughness on shock peak overpressure at the surface for all heights of burst was to lower the overpressures slightly. Surface roughness delayed the Mach stem formation at the greatest charge height and lowered the growth at all burst heights. A similarity parameter was found which approximately correlates the triple-point path at different burst heights.

Granular forms of common materials such as metals and ceramics, sands and soils, porous energetic materials (explosives, reactive mixtures), and foams exhibit interesting behaviors due to their heterogeneity and critical length scale, typically commensurate with the grain or pore size. Under extreme conditions of impact, granular and porous materials display highly localized phenomena such as fracture, inelastic deformation, and the closure of voids, which in turn strongly influence the bulk response. Due to the complex nature of these interactions and the short time scales involved, computational methods have proven to be powerful tools to investigate these phenomena. Thus, the coupled use of experiment, theory, and simulation is critical to advancing our understanding of shock processes in initially porous and granular materials. This is a comprehensive volume on granular and porous materials for researchers working in the area of shock and impact physics. The book is divided into three sections, where the first presents the fundamentals of shock physics as it pertains to the equation of state, compaction, and strength properties of porous materials. Building on these fundamentals, the next section examines several applications where dynamic processes involving initially porous materials are prevalent, focusing on the areas of penetration, planetary impact, and reactive munitions. The final section provides a look at emerging areas in the field, where the expansion of experimental and computational capabilities are opening the door for new opportunities in the areas of advanced light sources, molecular dynamics modeling, and additively manufactured porous structures. By intermixing experiment, theory, and simulation throughout, this book serves as an excellent, up-to-date desk reference for those in the field of shock compression science of porous and granular materials.