On the shock–vortex interaction in Schardin's problem

In this study we revisit Schardin's problem by investigating experimentally shock waves diffracting over a finite wedge and interacting with the tip vortices in a complicated manner. Holographic interferometry and shadowgraphy were used in a shock tube for a shock Mach number . Numerical simulations were carried out to obtain complementary flow data. The experimental results show that diverging acoustic waves are generated due to the interaction between shock waves and vortexlets along the slip layer. By means of the computational results obtained for short time intervals, and the corresponding optical images, analysis of the shock-vortex interactions became possible for extended time periods. Received 18 May 1998 / Accepted 4 March 1999     

Unsteady oblique shock waves

A spatially and temporally local analysis is provided for unsteady, oblique shock waves, in which the flow is assumed to be two-dimensional or axisymmetric. Three unsteady parameters, in a laboratory frame, are viewed as the known independent variables. These are the upstream Mach number, the shock Mach number, and the angle of the shock relative to the instantaneous upstream velocity. Other steady and unsteady parameters, such as the velocity turn angles and downstream Mach numbers, are evaluated in closed form, in terms of these three quantities. Trends are assessed, and a sensitivity analysis is provided. It is suggested that the theory may find application in converting a shock capturing algorithm, at an early time during the computational process, into a shock fitting algorithm. Received 30 April 1999 / Accepted 29 November 1999     

Shock-induced collapse of a cylindrical air cavity in water: a Free-Lagrange simulation

A Free-Lagrange CFD code is used to simulate the collapse of a cylindrical air cavity in water by a 1.9 GPa incident shock. The Lagrangian treatment allows the air/water interface to be tracked throughout the interaction. The incident shock is partially transmitted into the cavity, within which it experiences multiple reflections. The upstream cavity wall involutes to form a high-speed jet which, on impact with the far cavity wall, produces an intense blast wave. Heating of the gas within the cavity is highly non-isentropic, and is dominated by shock heating. The predicted final gas temperature is of order 12000 K, although the modelling assumptions used here lead to over-prediction of temperature during the later stages of collapse. Received 14 September 1999 / Accepted 28 June 2000     

An Efficient Method for Computing Hyperbolic Systems with Geometrical Source Terms Having Concentrations

We propose a simple numerical method for calculating both unsteady and steady state solution of hyperbolic system with geometrical source terms having concentrations. Physical problems under consideration include the shallow water equations with topography,and the quasi one-dimensional nozzle flows. We use the interface value, rather than the cell-averages, for the source terms, which results in a well-balanced scheme that can capture the steady state solution with a remarkable accuracy. This method approximates the source terms via the numerical fluxes produced by an (approximate) Riemann solver for the homogeneous hyperbolic systems with slight additional computation complexity using Newton‘s iterations and numerical integrations. This method solves well the subor super-critical flows, and with a transonic fix, also handles well the transonic flows over the concentration. Numerical examples provide strong evidence on the effectiveness of this new method for both unsteady and steady state calculations.     

Over forty years of continuous research at UTIAS on nonstationary flows and shock waves

Analytical and experimental research on non-stationary shock waves, rarefaction waves and contact surfaces has been conducted continuously at UTIAS since its inception in 1948. Some unique facilities were used to study the properties of planar, cylindrical and spherical shock waves and their interactions. Investigations were also performed on shock-wave structure and boundary layers in ionizing argon, water-vapour condensation in rarefaction waves, magnetogasdynamic flows, and the regions of regular and various types of Mach reflections of oblique shock waves. Explosively-driven implosions have been employed as drivers for projectile launchers and shock tubes, and as a means of producing industrial-type diamonds from graphite, and fusion plasmas in deuterium. The effects of sonic-boom on humans, animals and structures have also formed an important part of the investigations. More recently, interest has focussed on shock waves in dusty gases, the viscous and vibrational structure of weak spherical blast waves in air, and oblique shock-wave reflections. In all of these studies instrumentation and computational methods have played a very important role. A brief survey of this work is given herein and in more detail in the relevant references.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1990.     

Shock-wave equation-of-state studies at Los Alamos

A history of the shock-wave equation-of-state (EOS) studies at Los Alamos is given. Particular emphasis is placed on the pioneering research in the 1950s where many of the experimental techniques and methods of analysis were developed, which we now take for granted. A brief review of shock-wave physics is given, which illustrates important hydrodynamic and thermodynamic concepts. Recent studies on the EOS of Ti are presented with emphasis on the-to- phase transition. VISAR wave profiles for polycrystalline Ni and singlecrystal Ni are presented to determine the strengths of these materials under pressure. Low-density polystyrene foam Hugoniot experiments are described and results analyzed.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1990.     

Anti-miss-shot control device for selective stone disintegration in extracorporeal shock wave lithotripsy

A new device to prevent erroneously focused shock waves to the renal parenchyma during extracorporeal shock wave lithotripsy (ESWL) has been developed; an anti-miss-shot control device (AMCD) and experiments have been conducted to evaluate its effectiveness. For shock wave generation and stone localization, piezoceramic elements (PSE) and ultrasound localization, respectively were used. After stone localization, probing ultrasounds (PU) were emmitted from the PSE towards the focal region and the reflected sound levels (RSL) were monitored by the PSE which also functioned as a microphone. A direct hit by the PU to the stone or a miss was judged from the RSL, i.e. a high RSL indicates a direct hit and a low RSL indicates a miss. Shock waves were generated only when the RSL exceeded the level which indicated a direct hit. The experimental results showed that the injury to the renal parenchyma was decreased by using the AMCD. Clinical application of the AMCD is expected to increase the safety of ESWL.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1990.     

The reflected pressure field in the interaction of weak shock waves with a compressible foam

This paper deals with the waves that are reflected from slabs of porous compressible foam attached to a rigid wall when impacted by a weak shock wave. The interest is in establishing possible attenuation of the pressure field after a shock or blast wave has struck the surface. Foam densities from 14 to 38 kg/m³ were tested over a range of shock wave Mach numbers less than 1.4. It is shown that the initial reflected shock wave strength is accurately predicted by the pseudo-gas model of Gelfand et al. (1983), with a pressure ratio of approximately 80% of the value for reflection off a rigid wall. Evidence is presented of gas entering the foam during the early stages of the process. A second wave emerges from the foam at a later stage and is separated from the first by a region of constant velocity and pressure. This second wave is not a shock wave but a compression front of significant thickness, which emerges from the foam earlier than predicted by the pseudo-gas model. Analysis of the origin of this wave points to much more complex flows within the foam than previously assumed, particularly in an apparent decrease in average wave front speed as the foam is compressed. It is shown that the pressure ratio across both these waves taken together is slightly higher than that for reflection off a rigid wall. In some cases this compression wave train is followed by a weak expansion wave.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1990.     

Supercritical flow in manholes with a bend extension

 Bend manholes of sewers with 45° deflection angles are considered. Previous results are reconsidered by introducing the so-called bend extension. It is demonstrated that the discharge capacity of the 45°- and the 90°-bend manholes is identical if the bend extension, a U-shaped straight downstream portion, is added to the 45° manhole. In addition, the effect of the bend cover is analyzed as a general means to suppress shock waves. Both bend extensions and bend covers may be added to existing structures that convey discharge close to or over the design discharge. The hydraulics of bend manholes are analyzed in detail, including the wave profiles along the inner and the outer bend walls, the complete free surface, the recirculation zone, the pressure distributions on the walls and flow in the downstream sewer. Received: 12 March 2001 / Accepted: 10 August 2001     

Upstream porthole injection in a 2-D scramjet model

Injection from portholes upstream of the combustion chamber was investigated as a method of delivering fuel into a scramjet. This method reduces the viscous drag on a model by allowing a reduction in the length of the combustion chamber. At experimental enthalpies of 3.0 MJ/kg in the T4 shock tunnel, there was no evidence of combustion in the intake, either by shadowgraph or pressure measurements. Combustion was observed in the combustion chamber. A theoretical extension of these results is made to a hot wall scenario. Received 2 January 2001 / Accepted 3 August 2001