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This article describes the design and experimentation of a new anaerobic internal combustion engine using direct injection of liquid monopropellant. Specifically, the use of monopropellant post-injection allows the control of the profile P - V of the cycle, which significantly increases the mean effective pressure (indicated mean effective pressure) and the power density of the engine. The monopropellant used was isopropyl nitrate, which is the first known demonstration of a piston engine using this monopropellant for anaerobic operation. The engine power has been modulated with post-injection strategy to modify the P - V cycle profile to obtain a constant-pressure combustion in anaerobic mode. Experiments were performed using an engine with a single piston with a effective swept volume of 45 cm3, at an operating frequency of 2 Hz. The prototype engine has achieved an indicated mean effective pressure of up to 4.4 MPa and an indicated power up to 400 W. The indicated thermodynamic efficiency of the engine is found to be about 13% based on the isopropyl nitrate heat of explosion. The indicated specific fuel consumption of the engine is 2.5 mg/J, which represents a conversion efficiency of 49% based on the isopropyl nitrate specific energy.

This work examines the techno-economic viability for replacing, in remote Northern Canadian villages not connected to the grid, local diesel generation systems with a wind turbine potentially combined with compressed air energy storage and/or CO2 direct-air capture systems. The compressed air energy storage configurations analyzed include a geological reservoir at constant volume, a multi-stage compressor with intercooler, a multi-stage turbine and a heat exchanger. The direct-air capture technology analyzed uses a solid sorbent with temperature swing adsorption. The analysis is based on a model village of 1000 inhabitants with an average electrical demand of 1000 kW with daily morning and evening peaks, and a daily average effective capacity factor varying according to a sinusoidal probability density distribution. It is found that the direct-air carbon capture potential of a compressed air energy storage system appropriately sized for the present application is negligible owing to the small flow volume and low atmospheric CO2 concentration. Furthermore, the integration of compressed air energy storage does not lead to appreciable reductions in diesel generation and related carbon emissions. Overall, the most interesting cases considered in the present study use either the smallest wind turbine, sized for the average power demand, requiring the smallest initial investment, offering the fastest payback and reducing carbon emissions by 95% over the current case, or a wind turbine twice as powerful, covering most demand peaks, such that payback time doubles but overall carbon emission reductions are also doubled.

Conventional and compression-enhanced ejector refrigeration systems were investigated numerically using regular and retrograde refrigerants. The nature of retrograde fluids was explained, including their main advantages and disadvantages. The numerical model was developed and validated with previous experimental data of both types of working fluids. Energy and exergy analysis were performed to examine system performance and compare between the selected refrigerant candidates. Retrograde refrigerants were found promising with both versions of ejector cycles, when two case studies of an air conditioning application and an indoor ice rink were considered. The butene series showed superior coefficient of performance and exergy efficiency, especially the isomers cis-2-butene and 1-butene.

We report on the design and testing of a new minimally invasive device for crossing chronic total occlusions in the coronary and peripheral vasculature. The device is based on a novel shock wave generator that exploits inverse dispersion in solid waveguides to amplify the signal of broadband piezoelectric ultrasound transducers. Results of tests assessing the safety, efficacy, and mechanism of action of the device on a variety of surrogates, ex vivo arteries, and live animals are presented.

This work presents optical measurements of shock wave propagation in a glass micro-channel. This transparent facility, with a section ranging from 1 mm × 150 μm to 1 mm × 500 μm, exploits a high-speed schlieren videography to visualize the propagation of a shock wave within the micro-channel and to quantify velocity and boundary effects. In this paper, we focus on the Mach waves induced by wall roughness in the supersonic flow behind the wave.

We present sensor concepts eventually able to measure pressure pulses traveling in liquid metal, for example, for nuclear fusion applications. Two promising solutions have been tested and validated in water: a fast-response piezoelectric transducer mounted in a custom liquid-cooled housing and a stress bar where mechanical waves produced by the pressure pulse are dynamically measured using strain gauges.

BACKGROUND The aim of this study was to examine the safety and efficacy of the SoundBite™ Crossing System for the recanalization of infrainguinal chronic total occlusion (CTO) lesions. CTOs are frequent among patients with severe claudication or critical limb ischemia. Failure to recanalize CTOs remains common and is associated with poor prognosis. The SoundBite™ Crossing System (SoundBite Medical Solutions Inc., Montreal, QC, Canada) is a newly developed device that uses a 0.018-inch wire (SoundBite™ Active Wire) to deliver acoustic shock waves to the distal tip of a steerable guidewire to facilitate directed penetration of the proximal cap and crossing of the occlusion. METHODS Symptomatic patients with de novo infrainguinal CTOs from 3 centers were enrolled in a prospective, single-arm feasibility study. The primary endpoint was 30-day device success defined as composite of technical success, defined as penetration and progression within the CTO with the SoundBite™ Active Wire followed by complete recanalization, and freedom from device-related major adverse events including death, urgent amputation, clinically-driven target vessel revascularization, perforation, type ≥C dissection, or distal embolization requiring intervention. RESULTS Thirty-seven patients including 41 CTO lesions were enrolled in this study. CTO length ranged from 10 mm to 270 mm (mean 97.9±77.4 mm), and moderate-to-severe calcification was present in 24 (58.5%) of the treated lesions. CTOs were successfully crossed in 34 (91.9%) patients. No device-related adverse events occurred, resulting in a 30-day device success rate of 91.9%. Compared with baseline, 30-day ankle brachial index (0.66±0.24 versus 0.89±0.20; P

Chronic total occlusion (CTO) lesions are frequent in patients with peripheral and coronary artery disease, and associated with a higher risk of adverse events, including mortality, decreased quality of life, and increased health-care costs. Percutaneous intervention of CTO lesions has been associated with a lower procedural success rate, and current dedicated CTO devices may be of limited use for the non-CTO expert, and associated with increased intraprocedural complication rates. The SoundBite Crossing System (SoundBite Medical Solutions, Inc) is a newly developed device using shockwaves (short-duration, high-amplitude pressure pulses) to facilitate penetration of the proximal cap and crossing of the occlusion. The current report describes the first use of the SoundBite Crossing System in the recanalization of human ex vivo occluded arteries below the knee during a simulated procedure performed under fluoroscopy. Microcomputed tomography and histologic evaluation of the occluded and recanalized segment are provided to support therapeutic mechanism.

Chronic total occlusion (CTO) lesions are frequent in patients with peripheral and coronary artery disease, and are associated with a higher risk of adverse events, including mortality, decreased quality of life, and increased health-care costs. Percutaneous intervention of CTO lesions has been associated with a lower procedural success rate, and current dedicated CTO devices may be of limited use for non-CTO experts, and associated with increased intraprocedural complication rates. The SoundBite Crossing System (SoundBite Medical Solutions, Inc) is a newly-developed device using shockwaves (short-duration, high-amplitude pressure pulses) delivered to the tip of guidewire to facilitate penetration of the proximal cap and crossing of the occlusion. The current report describes the first-in-man use of the SoundBite Crossing System in the recanalization of two occluded lower-limb arteries.

Due to the high pressure and temperature state produced by shock waves, they offer the possibility to greatly speed up combustion processes as compared to diffusive reaction mechanisms. Devices exploiting shock-induced combustion also have the potential for higher compression ratios, and thus better efficiency, and less complexity than systems using mechanical compression systems. These advantages can lead to lighter, more efficient, and more compact propulsion and power systems.

High-g field combustion, such as in rotary ramjet engines, is a promising approach to reduce nitride oxides and combustor size by taking advantage of the flame acceleration due to the buoyancy of the products over the reactants. This paper presents a high-g field combustor design for a rim–rotor rotary ramjet engine. In this device, a premixed flow of air and fuel is ignited in the nonrotating inlet track and then swallowed and stabilized in the rotating combustion chamber. Outboard ignition frees the rotating structure from igniters, increasing the maximal tangential speed of the engine and thus its maximal efficiency. The rotating combustor design benefits from extreme centrifugal fields (105g to 107g) for both stabilizing the flame during ignition and maximize flame velocity. A simple buoyancy-driven combustion model allows estimating the combustor length and shows good agreement with numerical simulations, which demonstrate a combustion efficiency to be higher than 85%, even with some reactants bypass...

Producing closed-cell foams is generally cheaper and simpler than open-cell foams. However, the acoustic and filtration efficiency of closed-cell foam materials is generally poor because it is very difficult for fluid or acoustic waves to penetrate into the material. A new method using shock waves to remove the membranes closing the cell pores (known as reticulation) and thus to improve the acoustic and filtration behavior of closed-cell foam material is presented. Various shock treatments have been carried out on polyurethane and polyimide foams and the following conclusions were drawn: (1) reticulation efficiency increased and thus the airflow resistivity and tortuosity decreased when increasing the amplitude of the shock treatment; (2) the rigidity of the foam is decreased; (3) the process is reliable and repeatable and (4) obtained acoustic performance is comparable to classical thermal reticulation.

We present the results of a blowdown experiment to investigate the performance of a butene ejector. The blowdown configuration was selected for its flexibility and simplicity allowing for fast experimentation. The experiment featured an ejector where the primary, secondary and back pressure conditions are simulating those present in an ejector refrigeration cycle. The ejector was first tested with air and then 1butene refrigerant. Results showed that single- and double-choking conditions, as well as other well-known ejector features, could be achieved under various operating conditions. The validity of the acquired experimental results, based on the blowdown principle, was confirmed when the order of magnitude of the unsteady terms in the flow governing equations were found to be 10 5 to 10 7 times less than the steady terms. Displacing the primary nozzle positively towards the constant area section of the ejector increased both of the entrainment and compression ratios until an optimum position is reached, beyond which the entrainment ratio diminished. Based on the present experimental data, the estimated COP and mechanical COP values for a basic butene ejector cycle suitable for an indoor ice rink application ranged from 0.1 to 0.15, and from 9.2 to 13.7, respectively, when the evaporation temperature varied between −14.5 °C and −6.1 °C.

We present a novel intradermal needle-free drug delivery device which exploits the unsteady high-speed flow produced by a miniature shock tube to entrain drug or vaccine particles onto a skin target. A first clinical study of pain and physiological response of human subjects study is presented, comparing the new injector to intramuscular needle injection. This clinical study, performed according to established pain assessment protocols, demonstrated that every single subject felt noticeably less pain with the needle-free injector than with the needle injection. Regarding local tolerance and skin reaction, bleeding was observed on all volunteers after needle injection, but on none of the subjects following powder injection. An assessment of the pharmacodynamics, via blood pressure, of pure captopril powder using the new device on spontaneously hypertensive rats was also performed. It was found that every animal tested with the needle-free injector exhibited the expected pharmacodynamic response following captopril injection. Finally, the new injector was used to study the delivery of an inactivated influenza vaccine in mice. The needle-free device induced serum antibody response to the influenza vaccine that was comparable to that of subcutaneous needle injection, but without requiring the use of an adjuvant. Although no effort was made to optimize the formulation or the injection parameters in the present study, the novel injector demonstrates great promise for the rapid, safe and painless intradermal delivery of systemic drugs and vaccines.

A fully instrumented microscale shock tube, believed to be the smallest to date, has been fabricated and tested. This facility is used to study the transmission of a shock wave, produced in a large (37 mm) shock tube, into a 34 $\mathrm{\mu} \mathrm{m} $ hydraulic diameter and 2 mm long microchannel. Pressure microsensors of a novel design, with gigahertz bandwidth, are used to obtain pressure–time histories of the microchannel shock wave at five axial stations. In all cases the transmitted shock wave is found to be weaker than the incident shock wave, and is observed to decay both in pressure and velocity as it propagates down the microchannel. These results are compared with various analytical and numerical models, and the best agreement is obtained with a Navier–Stokes computational fluid dynamics computation, which assumes a no-slip isothermal wall boundary condition; good agreement is also obtained with a simple shock tube laminar boundary layer model. It is also found that the flow developing within the microchannel is highly dependent on conditions at the microchannel entrance, which control the mass flux entering into the device. Regardless of the micrometre dimensions of the present facility, shock wave propagation in a microchannel of that scale exhibits a behaviour similar to that observed in large-scale facilities operated at low pressures, and the shock attenuation can be explained in terms of accepted laminar boundary models.

The rim–rotor rotary ramjet engine is a new propulsion-system design with the potential to significantly improve power density and reduce complexity over conventional gas turbines, thus making it an interesting alternative for future transportation and stationary power systems. This paper presents a quasi-one-dimensional aerothermodynamic design model, taking into account the dominant physics of the rim–rotor rotary ramjet engine: 1) shock-wave compression, 2) high-g field combustion, 3) viscous losses, 4) heat transfer, 5) inlet and outlet periodic condition, and 6) windage losses. It is shown that high flame velocity due to buoyant forces leads to a very compact combustion chamber and possibly very low nitrogen oxides. A 500 kW rim–rotor rotary-ramjet-engine version is designed with the model and could produce 7:6 kW=kg at a tangential velocity of 1000 m=s, which is more than twicetheactualgas-turbinepowerdensity.Aproof-of-conceptprototypeistestedatlowspeed(Mach1),andshows good agreement with the model for both indicated power without combustion and windage losses. Combustion efficiency is measured to over 85% at 220;000g. These results confirm the design model capabilities, at least within the range of tested Mach numbers.

International audience; This paper presents the design and experimental results of a new micro gas turbine architecture exploiting counterflow within a single supersonic rotor. This new architecture, called the supersonic rim-rotor gas turbine (SRGT), uses a single rotating assembly incorporating a central hub, a supersonic turbine rotor, a supersonic compressor rotor, and a rim-rotor. This SRGT architecture can potentially increase engine power density while significantly reducing manufacturing costs. The paper presents the preliminary design of a 5 kW SRGT prototype having an external diameter of 72.5mm and rotational speed of 125,000 rpm. The proposed aerodynamic design comprises a single stage supersonic axial compressor, with a normal shock in the stator, and a supersonic impulse turbine. A pressure ratio of 2.75 with a mass flow rate of 130 g/s is predicted using a 1D aerodynamic model in steady state. The proposed combustion chamber uses an annular reverse-flow configuration, using hydrogen as fuel. The analytical design of the combustion chamber is based on a 0D model with three zones (primary, secondary, and dilution), and computational fluid dynamics (CFD) simulations are used to validate the analytical model. The proposed structural design incorporates a unidirectional carbon-fiberreinforced polymer rim-rotor, and titanium alloy is used for the other rotating components. An analytical structural model and numerical validation predict structural integrity of the engine at steady-state operation up to 1000 K for the turbine blades. Experimentation has resulted in the overall engine performance evaluation. Experimentation also demonstrated a stable hydrogen flame in the combustion chamber and structural integrity of the engine for at least 30 s of steady-state operation at 1000 K.

This paper reports on the design, microfabrication, characterization, and testing of the first instrumented micrometer-scale shock tube. This device was fabricated by a series of etching, deposition, and patterning processes of the different structural layers on a silicon substrate to first create an array of direct-sensing piezoelectric pressure sensors followed by the bonding of another substrate to create a microchannel. The resulting assembly is a rectangular channel with a hydraulic diameter of 34 μm and a length of 2000 μm, instrumented with five wall pressure sensors along its length. This device is used to characterize, for the first time, the propagation of shock waves at microscales, where transport effects such as wall friction and heat transfer are important. The results show shock-wave attenuation along the length of the microchannel in accordance with simple analytical models for these flows.

We present the results of a theoretical and experimental study into the influence of various putter head design features on the rotational dynamics of the ball following putter impact. It is found that ball launch conditions can be tailored by designing the putter head with the appropriate combinations of face loft, center of gravity and moment of inertia. Face treatments, such as inserts and grooves, effect the coefficient of restitution and friction coefficient at the contact point and thus provide additional design parameters to control the launch conditions of a putt. Experiments demonstrate that inserts and grooves can modulate the coefficient of restitution of the impact, but not in a manner that gets the ball rolling earlier for fixed length putts.

A one-dimensional model for the numerical simulation of transport effects in small-scale, i.e., low Reynolds number, shock tubes is presented. The conservation equations have been integrated in the lateral directions and three-dimensional effects have been introduced as carefully controlled sources of mass, momentum and energy, into the axial conservation equations. The unsteady flow of gas behind the shock wave is reduced to a quasi-steady flow by choosing a coordinate system attached to the shock. The boundary layer problem is thereby reduced to a laminar solution, similar to the Blasius solution, with the exception that the wall velocity can be nonzero. The resulting one-dimensional equations are then solved numerically using a two-step Lax-Wendroff/ MacCormack scheme with flux correction transport. For validation purposes, comparisons are performed against previously published shock structure and low Reynolds number shock tube experiments; good agreement is observed. The model has been used to predict the performance of a 10µm shock tube and the result of this simulation shows the possibility of shock wave disappearance at lower pressure ratios for a micro-scale shock tube.

The present study focuses on the noise generation mechanisms in outflow valves, which are commonly used in airplanes in order to regulate the cabin pressure and maintain a safe environment for the passengers. In order to make a detailed flow and acoustic investigation, experimental and numerical data are collected on a simplified 2D butterfly valve installed in a rectangular transparent channel. Two operating points are investigated : (a) a transient operating point at a flight altitude of 17 000 feet, where a high level tonal noise has been reported and creates acoustic nuisances in the cabin ; (b) the cruise condition operating point, that corresponds to a flight altitude of 40 000 feet, and where broadband noise may be reduced. Measurements of the far field noise and the wall static pressure as well as high speed Schlieren flow visualization are performed. They hightlight the very complex structure of the flow. Expansion waves and shock cells are observed at the upstream and downstream edges of the seal step, which are possible sources of tonal noise. Vortex shedding have also been observed for the transonic case, and might also generate tonal noise. In order to get a better understanding of the noise generation mechanisms, three-dimensional simulations of the experimental set-up are performed. They rely on steady or unsteady Reynolds-Averaged Navier-Stokes (Scale-Adaptive Simulations) computations and Large Eddy Simulations. All numerical results compare well with experiments on the mean flow. The unsteady simulations reveal strong shock oscillations on the forward-facing corner of the valve step and consequent strong vortex shedding when the jet shear layer interacts with this shock. The observed tonal noise is related to these two mechanisms and the shear layer instability upstream of the step, and the expansion fan on the backward-facing corner of the step. The LES also shows strong higher frequency peaks not yet available in the measurements that are clearly seen as the dominant noise-radiation mechanisms upstream of the valve in the dilatation field.

Intradermal powder injection is an emerging technology for the needlefree delivery of a potentially wide array of drugs and vaccines. Although needle injection of liquids is widespread principally because of its low cost, this delivery method is painful, generates dangerous medical waste and can cause contamination. Various technologies have been developed to address these shortcomings, amongst them creams, patches, inhalers and liquid jet injectors, each with their own severe limitations.

The majority of microsatellites in orbit do not have a propulsion system, which greatly limits their flexibility and their ability to perform complex tasks. Ambitious future missions will need the capability to produce the thrust required for either orbit change, drag makeup, station keeping or attitude control, and this usually requires more than one propulsion system [1].

Foam microstructure can be seen as a collection of interlinked struts forming a packing of cells interconnected to others through pores. Materials with a totality of pores closed by thin membranes are called closed-cell foams. The filtration and acoustic efficiency of closed-cell foams is poor compared to open-cell foams since it is very difficult for the fluid or the acoustic waves to penetrate inside the material.

Because of their fast response, piezoelectric pressure sensors are commonly used in applications involving acoustic or shock wave propagation to provide an accurate time-history of pressure at a certain point in the flow. However, it is often necessary to probe the flow at different locations, so that, for example, the direction and the speed of the waves can be inferred.

Cardiovascular disease is the leading cause of death worldwide. This disease includes chronic total occlusion (CTO), which is a complete blockage of an artery. Unlike partial occlusions, CTOs are difficult to cross percutaneously using conventional guidewires (thin and flexible wires) because of the fibrotic and calcified nature of the blockage. The lack of data regarding the mechanical properties of CTO limits the development of new technologies in the field of percutaneous coronary intervention (PCI) and percutaneous peripheral intervention (PPI). In this study, calcified plaques retrieved from occluded arteries are analyzed in order to better understand their mechanical properties and to help propose an artificial analogue. Calcified plaques samples were collected from the superficial femoral artery wall within one hour following a lower limb amputation surgery. These samples were studied to determine their composition and mechanical properties. The same characterization procedures were performed on various potential artificial analogues. These analogues include three plaster materials and dense hydroxyapatite blocks. The results were then compared with those of the calcified plaques in order to determine the more favorable analogue. This mechanical analysis and the proposal of a potential analogue for the calcified plaques found in occluded arteries could benefit the development of new technologies and devices in the field PCI and PPI.Copyright © 2014 by ASME

An apparatus to provide a safer and more efficient non-invasive treatment of kidney stones is under development. The proposed non-invasive alternative is to produce a tightly focused high-intensity cavitation cloud right at the stone; the cloud being electronically steerable in real time to compensate for the respiratory movements which would significantly reduce the exposition of healthy tissues to damaging shock waves. The piloted cloud is produced by 19 independent novel shock wave generators that are geometrically oriented towards a single focal point. The real-time steering is accomplished by applying different emission delays between the shock wave generators. The steering capability of the 19-channel prototype was monitored in vitro using a pressure sensor and kidney stone analogs. Promising tests were also conducted on ex-vivo pigs to measure the erosion rate of implanted artificial kidney stones.Copyright © 2014 by ASME

This paper reports on a series of indentation tests performed on ballistic gelatin (10%) and Perma-Gel. In these experiments, both gels were submitted to strain rates varying from 0.1 and 2.7 s−1 in quasi-static indentation. Two methods were used to evaluate the Young’s modulus from quasi-static indentation test: the Hertz theory and the Oliver-Pharr model. The dependence of strain rate was also analyzed. Finally, dynamic indentation tests were performed on both gels at frequencies of 0.1 and 1.0 Hz to evaluate the gel’s viscoelastic properties characterized by the storage modulus, the loss modulus and the phase angle.Copyright © 2014 by ASME

We present a model for the effects of scale, via molecular diffusion phenomena, on the generation and propagation of shock waves. A simple parametrization of the shear stresses and heat flux at the wall leads to the determination of new jump conditions, which show that, for a given wave Mach number at small scales, the resulting particle velocities are lower but the pressures are higher. Also, the model predicts that the flow at small scale is isothermal and that the minimum wave velocity can be subsonic. Experiments with a miniature shock tube using low pressures to simulate the effects of small scale have shown qualitative agreement with the proposed model. In fact, the effects of scale appear even more important than what has been incorporated in the model.

▪ Abstract The Richtmyer-Meshkov instability arises when a shock wave interacts with an interface separating two different fluids. It combines compressible phenomena, such as shock interaction and refraction, with hydrodynamic instability, including nonlinear growth and subsequent transition to turbulence, across a wide range of Mach numbers. This review focuses on the basic physical processes underlying the onset and development of the Richtmyer-Meshkov instability in simple geometries. It examines the principal theoretical results along with their experimental and numerical validation. It also discusses the different experimental approaches and techniques and how they can be used to resolve outstanding issues in this field.

The lack of a simple and effective wire for crossing chronic total occlusions (CTO) has led to the development of the SoundBite Crossing System. The SoundBite Crossing System is a recanalization tool, and is designed to assist placement of a conventional guidewire in the intraluminal space beyond

Experiments examining the interaction of shock waves with an interface separating two gases of different densities are reported. Flow visualization by the schlieren method and x-ray densitometry reveals that important secondary effects are introduced by the experimental apparatus, especially at the walls of the shock tube from shock wave/boundary layer interaction below, above, and at the interface itself. These effects can impair the observation of the primary phenomenon under study and can lead to the overall deformation of the interface. In particular, the thickness of the viscous boundary layer at the interface is computed using a familiar shock tube turbulent boundary layer model and the occurrence of bifurcation of reflected waves below and above the interface is successfully predicted based on classical bifurcation arguments. The formation of wall vortical structures at the interface is explained in terms of baroclinic vorticity deposition resulting from the interaction of reflected waves with the ...

Arrays of piezoelectric pressure sensors have been fabricated and tested. The sensor structure consists of a sol-gel derived PZT layer sandwiched between two platinum electrode layers, deposited on an oxidized silicon substrate. The devices were successfully used to simultaneously perform point-measurements of the amplitude, speed and direction of shock waves propagating in a shock tube.

The effect of varying the explosive sensitivity for a heterogeneous explosive formed of a packed bed of glass beads impregnated with liquid nitromethane (NM) sensitized with diethylenetriamine (DETA) is investigated. The changes in the dependence of critical charge diameter on bead size is investigated at concentrations of 5%, 10%, and 15% DETA over a range of bead diameters from 66 μm to 2.4 mm. Additional measurements are also performed on the critical diameter of the homogeneous liquid explosive itself. Three regions of behavior are identified for the bead-liquid explosive mixture. For bead sizes above approximately 1.5 mm, the critical diameter increases drastically as the amount of DETA is reduced from 15% to 10% and 5%. For bead sizes below approximately 1 mm, the critical diameter is nearly unchanged at concentrations of 10% and 15%. Between 1 and 1.5 mm, a region where the critical diameter increases sharply is found and detonation failure was observed in charge diameters of up to 60.5 mm. This transition region between the two others is found to be wider at lower DETA concentrations. This supports the previous proposition of two distinct mechanisms of detonation propagation which depend on the bead size: propagation through the pores of the media and propagation through the medium material itself.

The effects of viscosity and heat conduction, heat losses due to the wall heat transfer, as well as nonequilibrium phenomena can play an important role in microflows. Recent numerical investigations [1] of shock wave propagation in a microchannel with allowance for viscosity and rarefaction effects revealed significant differences from the inviscid theory, which ensures a correct description of the majority of specific features of macroflows. In that work, the shock wave was generated by breakdown of a diaphragm separating high-pressure and low-pressure domains.

Recent experiments on small shock tubes, at normal or reduced pressure, have revealed interesting phenomena. For example, Brouillette [1], using pressure instrumentation, has examined the operation of a 5.3 mm shock tube at initial pressures down to 1 mBar for diaphragm pressure ratios up to 105 and found a decrease in shock strength with decreasing scaling parameter ReD/L for a given diaphragm pressure ratio. Garen et al. [2], with an atmospheric 1 mm shock tube that used a quick opening valve instead of diaphragm, reached the same conclusions using laser differential interferometry observations.

As new biomedical and industrial applications of shock waves emerge, the need to accurately and economically generate shocks is becoming more critical. Since a very large potential resides in biology and medicine areas for diagnostic and therapeutic uses, shock waves need to be efficiently produced in cells, tissues and organs. In the past, there have been a number of methods used to produce shock waves in liquids, all characterized by a large and rapid energy deposition, either through the detonation of an explosive, the irradiation of a target with a pulse of laser energy, the dumping of electricity through a spark gap, or the sudden acceleration of a piston, either by electromagnetic or piezoelectric means. There are well known shortcomings associated with each of these methods, such as the requirement for high-voltage electronics, the manipulation of explosives and/or the lack of control over the shock properties [1]. This paper presents a new method to generate highamplitude pressure pulses in liquids exploiting the advantages of low amplitude piezoelectric generators.

Entry of a shock wave into a microchannel and its propagation in the channel are studied numerically by the continuum and kinetic approaches. It is shown that the shock wave is amplified immediately after it enters the microchannel. After that, the shock wave in an inviscid computation propagates over the microchannel with a constant velocity. In a viscous computation, the shock wave velocity decreases and the wave attenuates. Qualitative agreement between experimental data and viscous computations is demonstrated.

We present experiments on the isothermal gas flow at relatively high Mach numbers in microfabricated channels of small aspect ratios. The microchannels were fabricated by deep etching on silicon wafers, bonded to a Pyrex wafer to cover and seal them; the microchannels were 10 microns deep with a variety of widths. The accurate determination of the small flow rates was performed by measuring the displacement of a bead of mercury in a precision bore glass tube in a controlled environment. The experiment setup has been specially designed to account for inlet and outlet loss. The inferred friction coefficient at different values of Knudsen, Reynolds and Mach numbers shows that the flow inside the microchannel follows the classical laminar behavior over the range of experiments.Copyright © 2010 by ASME