Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 73-87).

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 169-172).

Unsteady shock waves are formed by the coalescence of pressure waves. The attenuationof pressure and shock waves in general is of great importance in a wide varietyof application such as vehicle performance, health and safety. Previous researcheshave been carried out on a variety of geometries to understand the physics. Theaim of this project is to advance the previous-state-of-the-art and to shed furtherlight into the fundamental physics associated with the shock wave interactions andphenomena. Shock wave attenuation was studied by using rough walls in a three-pipe system. The roughness at the walls is added by placing grooves on the upper and lower wallsof the junctions. The angles of the branch pipe were varied from 30 to 150 degrees. Shock wave interactions with a co-flow jet were also examined. All the experimentswere performed for driver gas (air) pressures of 4, 8, and 12 bar and atmosphericpressure within the driven section, giving theoretical Mach number of 1.34, 1.54, and1.66, respectively. Three different velocities, 114, 138, and 178 m/s, were used forthe co-flow jet. High-speed schlieren photography, particle image velocimetry (PIV),and pressure measurements techniques were employed to visualise and quantify theflow field. Expansion and compression waves produced by the grooves led to a highly unsteadyflow field, an increase to the pressure upstream, and the formation of asecondary shock wave. The pressure of the incident shock front was reduced by anestimated 20%. A maximum of 10% reduction of velocity of the shock front at theexit was achieved. The shock vortex/ structure led to multiple reflections, distortionof the vortical field, a lambda-shock configuration and pressure fluctuations. Theinfluence of the co-flow jet dissipated the shock/vortex structure, and attenuatedthe pressure peaks caused by multiple reflections. Complementing this investigation the testing of pressure sensitive paints (PSP)for the use of unsteady and high speed flows was carried out. The results showedthat the use of luminophores with high intensity output, and pressure sensitivityapplied on a porous material were the most suitable PSPs for these applications.

With recent improvement in wood manufacturing technologies, taller and larger wooden structures are being constructed, thereby increasing the risk for potential damage due to a blast threat against such structures. Recent studies on the effects of high strain rate in wood have been undertaken, however the vast majority of these studies have focussed on structural elements with idealized boundary conditions. Some studies included realistic connections as the boundary conditions, but little progress has been made to date in order to quantify the behaviour of connections in isolation. The current study aims to investigate the response of steel-wood-steel bolted connections when subjected to blast loads. This includes determining the dynamic increase in resistance and stiffness for stocky and slender bolts in both the parallel and perpendicular to grain directions. The study also explores analytical solutions to predict the joint behaviour and discusses the validity of current blast design provisions. Bolted wood connections were investigated under both static and simulated blast loading using the University of Ottawa’s shock tube. The study found a dynamic increase in resistance and stiffness when the failure mode was dominated by wood crushing in both the parallel and perpendicular to grain directions. No increase in resistance or stiffness was observed when bolt yielding dominated the failure. A loss of ductility was observed under dynamic loading for the parallel to the grain connections designed to fail in wood crushing. It was found that the use of self-tapping screw reinforcement was an effective method of preventing premature splitting failures and enhancing the performance of a connection. The results showed that connections which engaged the fastener in bending exhibited more favourable behaviour than connections which engaged only in wood crushing. A two degree-of-freedom model was capable of modelling the connections even when the support frame system had some flexibility. The validated model was used to investigate cases where the connection could contribute to the energy dissipation. It was found that the performance of the assembly improved when the connections were considered. Recommended future work includes an investigation of brittle failure modes in bolted connections, exploring connections with more deformation capacities, and expanding the experimental component of the study to include full-scale structural assemblies with wood elements and boundary connections. Limited design recommendations have been proposed in the current study, however testing at the assembly level could shed more light on such an important topic.

Shock wave lithotripsy is the preferred treatment modality for kidney stones in the United States. Despite clinical use for over twenty-five years, the mechanisms of stone fragmentation are still under debate. A piezoelectric array was employed to examine the effect of waveform shape and pressure distribution on stone fragmentation in lithotripsy. The array consisted of 170 elements placed on the inner surface of a 15 cm-radius spherical cap. Each element was driven independently using a 170 individual pulsers, each capable of generating 1.2 kV. The acoustic field was characterized using a fiber optic probe hydrophone with a bandwidth of 30 MHz and a spatial resolution of 100 μm. When all elements were driven simultaneously, the focal waveform was a shock wave with peak pressures p+ =65±3MPa and p−=−16±2MPa and the −6 dB focal region was 13 mm long and 2 mm wide. The delay for each element was the only control parameter for customizing the acoustic field and waveform shape, which was done with the aim of investigating the hypothesized mechanisms of stone fragmentation such as spallation, shear, squeezing, and cavitation. The acoustic field customization was achieved by employing the angular spectrum approach for modeling the forward wave propagation and regression of least square errors to determine the optimal set of delays. Results from the acoustic field customization routine and its implications on stone fragmentation will be discussed. / National Institutes of Health DK043881

Breast muscles that are deboned prior to 4 to 6 h postmortem are highly variable and lacking in tenderness. The poultry industry currently provides costly storage space for intact broiler breasts during this 4 to 6 h period. This thesis evaluates tenderization techniques that if effective could eliminate the need for this additional 4 to 6 h storage time. The first objective of this study was to determine a relationship between Warner-Bratzler shear values (WBS) (1 cm by 1cm, variable length strips) and consumer tenderness acceptability of broiler breasts. The breasts were divided into five groups based on their WBS values. Consumers were presented with one sample (1 cm by 1 cm by 2 cm strips) at a time and asked to report the acceptability of the sample's tenderness on a 9-point hedonic scale. Of the 62 panelists, 93.5 % found chicken breasts with WBS values from 2.1 to 3.1 kg to be acceptable. Only 83.9 % of the panelists found the extremely tender chicken breast to be acceptable (1.1 to 1.9 kg). The percentage of consumers that found the samples acceptable decreased as the WBS values increased beyond 3.1 kg (P<0.05). The second objective determined the effects of high pressure hydrodynamic shockwave (HSW) on tenderness (48 h postmortem) of early-deboned (52 min postmortem) breasts treated 25 minutes after deboning (70 min postmortem) or treated after storage (24 hr postmortem) and compared to the corresponding non-treated companion breasts. The effect of HSW treatment on early-deboned treated 25 min after deboned broiler breasts was determined by the following methods. Live broiler chickens were obtained from a commercial poultry company and slaughtered according to commercial processing standards. The effect of HSW on early deboned stored broiler breast was examined by deboning broiler breasts 45 min postmortem and storing (4 C) for 24 h. One breast from each bird was treated with hydrodynamic shockwave, while the companion breast was used as a control. Packaged breasts were placed in the center of a 20.23 cm diameter cylinder which was vertically positioned in the bottom of a water-filled HSW hemishell tank (30.4 cm diameter) and a shockwave was produced by and a shockwave was produced by detonating 40 grams of molecular explosive in the water. Early deboned (ED) breasts stored 24 h before treatment (2.5 kg, WBS) were 42% more tender than the companion ED control breasts (4.3 kg, WBS). The HSW treated breasts would be acceptable to approximately 94 % of consumers. The ED control breasts would be acceptable to only 67.7% of consumers. Early deboned and treated 25 min after deboning breasts (5.0 kg) were not different in WBS from their companion ED control breasts (4.6 kg). Early-deboned breasts treated immediately may require higher pressure shockwaves or delayed treatment. The HSW process can overcome the problem with tenderness associated with early deboning if the breasts are processed after storage thereby providing processors with the option to debone earlier. A third objective was to examine the effects of electrically produced shockwaves on early deboned broiler breasts and normally processed turkey breast. Broiler breasts were treated with one Pulse Firing Network (PFN) or two PFN and 45 % Energy. Breasts treated with one PFN were not different than controls. Broiler breasts exposed to two PFN were 22 % more tender and different from the controls. Turkey breast portions exposed to two PFN and 72% Energy were different (12 % lower WBS values) from the control breast portion. Electrically produced shockwaves can tenderize stored, early deboned chicken breasts and aged turkey breasts. / Master of Science

The overarching goal of this work is to advance the current knowledge of hydrodynamic instabilities (namely, Richtmyer-Meshkov and Kelvin-Helmholtz instabilities) and associated turbulent mixing phenomena which is important for several emerging technologies and verification/validation of numerical models being developed to study these phenomena. Three experimental campaigns were designed to focus on understanding the evolution of the instability under different impulsive acceleration histories and highlight the impact of initial conditions on the developing turbulent flow environment. The first campaign highlights the importance of initial baroclinic torque distribution along the developing shocked interface in a twice-shocked variable-density flow environment. The second campaign is a parametric study which aims at providing a large dataset for validating models in literature as well as simulations. In the last study, a new type of initial condition was designed to study the effect of initial conditions on late time turbulent flows. A description of the optical diagnostic techniques developed in our laboratory in order to complete these studies will be given. Now each campaign will be introduced. In the first campaign, an inclined interface perturbation is used as the initial condition. The Mach number (1.55), angle of inclination (60 degrees), and gas pair (N2/CO2) were held constant. The parameter which changed was the distance that the initial condition was placed relative to the end of the shock tube (i.e., the end of the test section). Three distances were used. The vorticity distribution was found to be very different for the most developed case after reshock. Furthermore, the most developed case started to develop an inertial range before reshock. The second campaign is parametric and seeks to test a proposed inclined interface scaling technique. The data is also useful for comparing to Ares simulation results. The parameter space covered Mach number (1.55 and 2.01), inclination angle (60 degrees and 80 degrees), and Atwood number (0.23 and 0.67). PLIF was developed and used to collect data for four cases before and after reshock. Linear and nonlinear cases developed very differently before reshock, but their mixing widths converged after reshock. The last campaign involves a new perturbation technique which generates what will be referred to as a complex interface. Counter-flowing jets were placed near the interface exit ports to create shear. The perturbation was made more complex by also injecting light (heavy) gas into the heavy (light) one. Density and velocity statistics were collected simultaneously. The complex case retained a signature of the inclined interface perturbation at late time before reshock and developed a larger inertial range than its inclined interface counterpart. Important parameters for a variable-density turbulence model are also presented.

High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. In the initial explosive dispersal, a dense gas-solid flow can exist where the physics of phase interactions are not well understood. A dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. The initial packed granular bed is produced by compressing loose aluminum oxide powder into a 6.35 mm thick wafer with a particle volume fraction of 0.48. The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle-shock interaction was obtained. Due to the limited strength of the Mach 2 incident shock wave, no transmitted shock wave is produced. The initial “solid-like” response of the particle wafer acceleration forms a series of compression waves that coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle break-up starts at local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-09-25 14:15:37.615

De nos jours, la sécurité des installations publiques, industrielles ou militaires est une problématique majeure. Les phénomènes de détonations en champ libre sont bien connus et documentés. Néanmoins les modèles et les lois mises en place ne s’appliquent pas dans le cas d’explosions confinées.Les travaux présentés dans ce mémoire de thèse portent sur l’étude de la propagation des ondes de choc dans des géométries simples et fermées. Différents paramètres ont été étudiés tels que l’influence du volume, de la position d’amorçage ou encore de la taille de l’évent.Les essais réalisés à petite échelle, dans deux maquettes expérimentales ont permis de mettre en place des lois prédictives portant sur les principaux paramètres de l’onde de choc incidente et réfléchie que sont la surpression maximale, le temps d’arrivée ainsi que l’impulsion.Ces lois ont ensuite été implémentées dans un code de calculs permettant d’automatiser la recherche des réflexions et des différents paramètres associés dans des configurations géométriques simples. / Nowadays, the security of public, industrial or military area is a major concern. Free-field blast are well known and documented. Nevertheless, the models and laws developed do not apply in case of confined explosions. The study focuses on the propagation of shock waves in simple closed geometries. Various parameters have been studied such as the volume, the charge position or the size of vents. The small scales experiments carried out in two experimental models, made it possible to set up predictive laws on the main parameters of the incident and reflective shock wave, such as the maximum overpressure, the arrival time and the impulse.These laws were then implemented in a calculation program to automate the search of reflections and associated parameters in simple geometric setup.

Student Number: 0008522F Master of Science Faculty of Engineering & The Built Environment School of Mechanical, Industrial & Aeronautical Engineering / An aircraft travelling at supersonic speeds close to the ground generates a bow wave, which is reflected off the ground surface. When the aircraft enters a valley, the three-dimensional bow wave is reflected off the valley walls, such that it could focus behind the aircraft. Complex threedimensional wave surfaces will result. The real situation of an aircraft entering a valley can be modelled and tested experimentally in a shock tube. To simulate the process a planar shock wave, generated in a shock tube, is moved over several notched wedge configurations. Schlieren photographs were produced to identify the resulting complex three-dimensional wave structures and then verified by three-dimensional CFD. The valley geometries investigated are rectangular, triangular, parabolic and conical. Three hill geometries were also investigated. The three-dimensional reflected surfaces from the rectangular valleys were found to vary only slightly as the valley floor inclination is increased. As the incident wave interacts with both the wedge and valley floor surfaces two prominent reflections occur. A primary reflected wave surface is generated from regular reflection off the wedge. This surface flows over into the valley contacting the incident wave at a second contact point. A secondary reflected wave is found underneath the primary reflected wave, generated due to Mach reflection occurring over the full width off the valley floor. The area of the incident wave between the second contact point and the triple point is seen to bow out into the downstream flow. The Mach stem of the reflection off the valley floor tends to become less pronounced for the larger valley floor inclination angles. In all the rectangular valleys, a shear layer is present, cascading down the valley wall and then along the valley entrance. The shear layer tends to decrease in size as the valley floor inclination increases. Both prominent reflected shock surfaces are almost conical in nature at close proximity to the valley wall. The triangular valleys show similar reflection patterns as the rectangular valleys. As the incident shock wave initially interacts with the wedge surface only regular reflection occurs. The resulting reflected wave forms the primary reflected surface which flows over into the valley. The reflection changes to Mach reflection as the incident wave interacts with the valley floor. The Mach stem of the reflection off the valley floor increases in characteristic height as one moves from the valley entrance wall to the plane of symmetry. The Mach stem is much smaller for the higher valley floor inclinations. A secondary reflected wave is found underneath the primary reflected surface. The secondary wave is Mach reflection near the plane of symmetry which turns iii to regular reflection closer to the valley wall. The primary and secondary reflected surfaces merge near the plane of symmetry and again along the wedge surface. A shear layer is found to cascade down the valley entrance wall for all geometries, decreasing in strength as the valley inclination angle increases. The parabolic valleys show similar reflection patterns as the triangular valleys. As the incident wave interacts with both the wedge and valley surfaces two reflections occur. The reflection off the wedge surface is regular. As the incident wave flows over into the valley the initial reflection off the valley floor is regular. This regular reflection then turns into Mach reflection the closer one moves to the symmetry plane. The Mach reflection off the valley floor forms a secondary reflected wave underneath the primary reflected wave that is found to flow over into the valley. The primary reflected wave contacts the incident wave at a second contract point found above the triple point. This contact point moves closer to the triple point and eventually along the secondary reflected wave as the incident wave advances downstream. The second contact point at a single time instant is also seen to move closer to the triple point as one moves closer to the plane of symmetry. A shear layer is found cascading down the valley entrance wall. The secondary reflected wave of the Mach reflection off valley floor forms a semi-circular surface which contacts the floor just after the shear layer. The Mach reflection off the valley floor changes to regular reflection as the surface begins to climb up along the valley entrance wall. The conical valleys once again show similar reflection patterns as those found in the other valley geometries. As the incident wave interacts with both the wedge and valley surfaces two reflections occur. Regular reflection occurs off the wedge surface with the resulting primary reflected wave flowing over into the valley. This primary reflected wave contacts the incident shock at a second contact point in the valley. The reflection off the valley floor is regular close to the valley entrance wall changing to Mach reflection nearer the symmetry plane. The reflected wave from the Mach reflection forms the secondary reflected surface found beneath the primary reflected wave. The secondary reflected Mach wave changes to regular reflection as the surface nears the valley wall, with the reflection point travelling along the valley floor until coincident with the valley entrance wall, where it then travels along the entrance wall. The second contact point found on the incident wave is found above the triple point and moves down the incident shock to eventually coincide with the triple point. A weak shear layer is found to cascade down the valley entrance wall. A weak separation also occurs at the entry point of the valley. iv The three hill geometries, triangular, parabolic and conical, all display similar reflection patterns. As the incident wave advances downstream regular reflection occurs off both the wedge and hill surfaces. The reflected waves come together at a point off the surface. At this point a double triple point occurs with two resulting Mach stems. One Mach stem contacts the wedge surface while the other contacts the hill surface. The resulting double Mach stem surface wraps around the base of the hill getting progressively tighter the closer it gets to the incident wave. The only major differences between all three geometries is the shape of the resulting reflected wave off the hill surface (which tends to follow the same geometric shape as the hill) and the distance between the two triple points for the conical and parabolic hills tends to be larger than that found for the triangular hill.