L'interaction entre une onde de choc plane et un nuage de gouttes d'eau homogène, monodisperse est étudiée dans un tube à choc. Les influences de la fraction volumique d'eau, αd(1 %, 0.3 % et 0.1%), rapport du volume d'eau sur le volume du nuage, de la hauteur du nuage Hd (70 cm, 40 cm et 15 cm), du diamètre des gouttes φd (250 µm et 500 µm ) et du nombre de Mach M (1.3 et 1.5) sont étudiées pour des fractions volumiques inférieures au pour cent. Lors de cette interaction, la pression en paroi du tube à choc est mesurée et la visualisation du nuage est obtenue par une méthode ombroscopique directe. Une évolution temporelle caractéristique de la pression induite par la propagation d'une onde de choc dans un tel milieu, est mise en évidence. Cette allure, diffère significativement de celle obtenue avec un nuage constitué de particules solides: la fragmentation des gouttes en est responsable. Une zone où la pression diminue directement après le pic de pression est alors observée aux stations de mesure localisées dans le nuage. L'atténuation de la surpression est mise en évidence: elle peut atteindre 80% du pic de pression mesuré sans nuage. Dans la partie numérique de ce travail, deux modèles de fragmentation sont implémentés, comparés et validés dans un code de calcul monodimensionel, instationnaire, Eulérien appliqué aux écoulements dilués (αd<1 %). On montre que la formulation du taux de production des gouttes selon le taux d'accroissement soit de leur nombre, soit de leur diamètre doit être utilisée respectivement soit avec, soit sans la prise en compte l'étape de déformation de la fragmentation. / The interaction between a planar shock wave and an both homogeneous and monodispersed droplet water cloud is studied in a shock tube. The effects of the water volume fraction αd (1% %, 0.3 % et 0.1%), ratio between the volume of water and the volume of the cloud, the height of the two-phase medium Hd (70 cm, 40 cm et 15 cm), the droplets diameters φd (250 µm et 500 µm ) and the Mach number M (1.3 et 1.5) are studied for a volume fraction smaller than one per cent. During this interaction, the pressure is measured and the visualization of the cloud is obtained by direct shadowgraphy. A characteristic temporal evolution of the pressure induced by the propagation of the shock wave in such a mixture is highlighted. This behavior differs significatively from the one obtained with a solid particles cloud : the droplet atomization is responsible of this change. A zone where the pressure decreases directly after the pressure peak is observed at different stations located into the water cloud. The mitiagtion of the overpressure is shown: it can reach 80%of the pressure peak measured without cloud. In the numerical part, two fragmentation models are added, compared and validated in a comptutational, one dimensional, instationnary, Eulerien code in the case of dilute flows (αd<1 %). We show that the formulation of the production rate of droplets defined by the number of droplets growth, or the diameter droplet growth, must be used, respectively, with and without taking into account the deformation stage of the droplet breakup. Thus, the numerical results are in good agrement with those obtained experimentally.

Die Rußbildung in der Pyrolyse von n-Hexan, Benzol und Kohlenwasserstoffen im Stoßrohr wird mit hoher Zeitauflösung absorptionsspektroskopisch beobachtet und Gasproben durch ein besonders schnelles Ventil gesammelt. Vom Beginn der Pyrolyse bis zum Einsetzen der Rußbildung wurde stets eine Induktionszeit beobachtet, deren Dauer von der Temperatur, der Kohlenstoffkonzentration und der Struktur des pyrolysierten Kohlenwasserstoffs abhängt. Dieser Zusammenhang wird mit einem Arrhenius-Ansatz beschrieben. Der Vorfaktor A ist für Aromaten eine Größenordnung kleiner als für Alkane. Die scheinbare Aktivierungsenergie beträgt (220 ± 10) kJ/mol. Das Rußmassenwachstum, das der Induktionsperiode folgt, wird mit einem Gesetz erster Ordnung beschrieben. Durch Normierung der Geschwindigkeitskonstanten auf die Kohlenstoffdichte zeigt, daß das Rußmassenwachstum in Pyrolysen und in vorgemischten Ethylenflammen vergleichbar schnell abläuft. Die Rußausbeute der Aromaten und Acetylen hat bei bei 1800 K ein Maximum. Für Ethylen und Alkane liegt diese charakteristische Temperatur um rund 100 K höher. Neben Ruß und Wasserstoff sind Acetylen gefolgt von Methan und Ethylen die wichtigsten Hauptprodukte. Die polycyclischen Aromaten tragen keine Seitengruppe und enthalten maximal einen Fünfring. Der Rußpartikeldurchmesser ist im Bereich von 30 nm. Der Einfluß von Eisenpentacarbonyl auf die Rußbildung ist gering.

This thesis recounts the experimental study of the dynamic response of a blast resistant glazing system to explosive loading. A combination of triaxial force sensors, pressure gauges, and laser displacement gauges capture the response in detail over a wide range of scenarios. The scenarios include low level blast loading to characterize the reaction at points around the perimeter of the window, moderate level blast loading to examine the repeatability of the blast scenario, and high level blast loading to capture the response during failure as the tensile membrane forms. The scenarios are modeled via an analytical Single-Degree-of-Freedom model as well as finite element modeling in ANSYS Explicit Dynamics. In addition, this study investigates some of the differences between experimental data and the predictions made by modeling.

The emerging paradigms of shockwave research have opened up new horizons for interdisciplinary applications. This has inevitably driven research towards studying the propagation of shockwaves in miniature shock tubes (tube diameters typically in the range of 1−10 ). Studies have revealed that while operating at this diameter range and low initial pressures (typically 1 < 100 ) leading to low values of characteristic Reynolds numbers (typically ′ < 23,000 −1), results in the boundary layer playing a major role in shockwave attenuation. But there are very few studies addressing shockwave attenuation when shock tubes are operated at higher Reynolds number. Pressure measurements and visualization studies in shock tubes of these length scales are also seldom attempted due to practical difficulties. Given that premise, in the present work the shockwave attenuation due to wall effects and non-ideal diaphragm rupture in shock tubes of hydraulic diameters 2 , 6 and 10 has been investigated at ambient initial driven section conditions ( 1 = 300 and 1 = 1 resulting in Reynolds number in the range 70,212 −1 – 888,627 −1). In this study pressure measurements and high-speed visualization have been carried out to find the effect of the pressure ratio, temperature ratio and molecular weights of driver gas on the shock attenuation processes. In order to study the effects of the driver/driven gas temperature ratios on the shock attenuation process, a new in-situ oxyhydrogen (hydrogen and oxygen gases in the ratio 2:1) generator has been developed. Using this innovative device, the miniature shock tubes are also run in the detonation mode (forward facing detonation wave). The results obtained using helium and nitrogen driver gases for these shock tubes reveal that as the hydraulic diameter of the shock tube is reduced, a larger diaphragm pressure ratio is required to obtain a particular strength of shockwave. The attenuation in the shockwave is found to be a function of the driver gas properties namely specific heat ratio ( 4), molecular weight ( 4), temperature ( 4) as well as the diaphragm opening time of the shock tube in addition to the parameters , 21, / , and 1 as already suggested in previous reports. The visualization studies reveal that the effect of diaphragm opening time leading to longer shock formation distances appears to influence the shockwave attenuation process at these shock tube diameters. Further, it is also found that the strength of the shockwave reduces when the ratio 4/ 1 is higher. It is also seen that the length of the driven sections must be less than twice the length of the driver sections to reduce attenuation. Based on the understanding of the nature of supersonic flow in a miniature shock tubes, a novel shock/blast wave device has been developed for certain innovative biotechnology applications such as needleless vaccine delivery and cell transformations. The new device has an internal diameter of 6 and by varying the length of the driver/driven sections either shock or blast waves of requisite strength and impulse can be generated at the open end of the tube. In the shock tube mode of operation, shockwaves with steady time duration of up to 30 have been generated. In the blast tube mode of operation, where the entire tube is filled with oxyhydrogen mixture, shockwaves with peak pressures of up to 550 have been obtained with good repeatability. An attempt to power this device using solar energy has also given successful results. Visualization of the open end of the detonation driven shock tube reveals features typical of flow from the open end of shock tubes and has helped in quantifying the density field. The subsequent instants of the flow resemble a precursor flow in gun muzzle blast and flash. Typical energy levels of the shock/blast waves coming out this device is found to be about 34 for an oxyhydrogen fill pressure of 5.1 in the shock tube operation mode. Transformation of E.coli, Salmonella Typhimurium and Pseudomonas aeruginosa bacterial strains using the device by introducing plasmid DNA through their cell walls has been successfully carried out. There is more than twofold increase in the transformation efficiency using the device as compared to conventional methods. Using the same device, needleless vaccine delivery in mice using Salmonella has also been demonstrated successfully. Overall, in the present thesis, a novel method for generating shockwaves in a repeatable and controllable manner in miniature scales for interdisciplinary applications has been proposed. Also, it is the first time that experiments with the different diameter miniature shock tubes have been carried out to demonstrate the attenuation of shockwaves as the hydraulic diameter of the shock tube decreases. Future research endeavors will focus on quantitative measurement of the particle velocity behind the shock waves, and also on the nature of the boundary layers to further resolve the complex flow physics associated with supersonic flows in these miniature shock tubes.

Recent events including deliberate terrorist attacks and accidental explosions have highlighted the need for comprehensive research in the area of structural response to blast loading. Research in this area has recently received significant attention by the civil engineering community. Reinforced Concrete (RC) water reservoir tanks are an integral part of the critical infrastructure network of urban centers and are vulnerable to blast loading. However, there is a lack of research and knowledge on the performance of RC reservoir walls under blast loading. The objective of this research study is to experimentally investigate the performance of reinforced concrete reservoir walls subjected to blast loading and to analyze the structural response. This study provides experimental test data on the performance of reinforced concrete reservoir walls under blast loading and complementary analytical predictions using the Singe-Degree-Of-Freedom (SDOF) analysis method. The reservoir walls in this study were designed according to the water volume capacity using the Portland Cement Association (PCA 1993) methodology. The design was validated using software SAP 2000. The experimental program involved the construction and simulated blast testing of two RC reservoir wall specimens with different support conditions: (1) two opposite lateral edges fixed, bottom edge pinned and top edge free; and (2) two opposite lateral edges fixed, and bottom and top edges free. The first boundary condition was intended to promote two-way bending action, while the second was dominated by one-way bending. The two specimens were each subjected to a total of six consecutive incrementally increasing blast tests. The experimental program was conducted in the shock tube testing facility that is housed in the University of Ottawa. Wall displacements, reinforcement strains, and reflected pressures and impulses were measured during testing. Analytical calculations were conducted using the equivalent SDOF method to simulate the dynamic response of the RC reservoir wall specimens under different blast loadings. Published tables, charts and coefficients contained in Biggs (1964) and UFC 3-340-02 (2008) were adopted in the equivalent SDOF calculations. The analytical results were compared against the ii experimental data. The SDOF method predicted smaller displacements than those recorded during testing. The approximate nature of the parameters and tables used in the equivalent SDOF calculations contributed to the discrepancy between the analytical and experimental results. Furthermore, assumptions regarding the support conditions and neglecting residual damage from previous blast tests contributed to the underestimation of the displacements.

The motion of shock waves is important in many fields of engineering and increasingly so with medical applications and applications to inertial confinement fusion technologies. The flow structures that moving shock waves create when they encounter a change in area is complex and can be difficult to understand. Previousresearchers have carried out experimental studies and many numerical studies looking at this problem in more detail. There has been a discrepancy between numerical and experimental work which had remained unanswered. One of the aims of this project is to try and resolve the discrepancy between numerical and experimental work and try to investigate what experimental techniques are suitable for work of this type and the exact way in which they should be applied. Most previous work has focused on sharp changes in geometry which induce immediate flow separation. In this project rounded corners will also be investigated and the complex flow features will be analyzed.Two geometries, namely a sharp 172 degree knife-edge and a 2.8 mm radius rounded corner will be investigated at three experimental pressure ratios of 4, 8 and 12 using air as the driver gas. This yields experimental shock Mach numbers of 1.28, 1.46 and 1.55. High-speed schlieren and shadowgraph photography with varying levels of sensitivity were used to qualitatively investigate the wave structures. Particle image velocimetry (PIV), pressure-sensitive paint (PSP) and traditional pressure transducers were used to quantify the flow field. Numerical simulations were performed using the commercial package Fluent to investigate the effect of numerical schemes on the flow field produced and for comparison with the experimental results. The sharp geometry was simulated successfully using an inviscid simulation while the rounded geometry required the addition of laminar viscosity. Reynolds number effects will be only sparsely referred to in this project as the flows under investigation show largely inviscid characteristics. As the flow is developing in time rather than in space, quotation of a distance-based Reynolds number is not entirely appropriate; however, Reynolds number based on the same spatial location but varying in time will be mentioned. The density-based diagnostics in this project were designed to have a depth of field appropriate to the test under consideration. This approach has been used relatively few times despite its easy setup and significant impact on the results. This project contains the first quantative use of PIV and PSP to shock wave diffraction. Previous studies have almost exclusively used density-based diagnostics which, although give the best impression of the flow field, do not allow for complete analysis and explanation of all of the flow features present. PIV measurements showed a maximum uncertainty of 5% while the PSP measurements showed an uncertainty of approximately 10%.The shock wave diffraction process, vortex formation, shear layer structure, secondary and even tertiary expansions and the shock vortex interaction were investigate. The experimental results have shown that using one experimental technique in isolation can give misleading results. Only by using a combination of experimental techniques can we achieve a complete understanding of the flow field and draw conclusions on the validity of the numerical results. Expanding the range of the experimental techniques currently in use is vital for experimental aerodynamic testing to remain relevant in an industry increasingly dominated by numerical research. To this end, significant research work has been carried out on extending the range of the PSP technique to allow for the capture of shock wave diffraction, one of the fastest transient fluid processes, and for applications to low-speed flow (< 20 ms−1).

Windows in building façade are vulnerable to blast pressures. When subjected to blast shock waves, glass windows may suffer failures, potentially causing serious injuries and casualties to the building occupants due to the flying glass shards and other projectiles. Protective films and laminated glass are widely used to protect windows against blast loads. These techniques have proven to reduce or prevent hazards associated with glass breakage. The use of steel or strengthened aluminum frames also reduce window blast hazards associated with frame failures. However, such measures are not always sufficient to mitigate the blast hazard if window retention anchors do not have sufficient resistance to blast pressures. Research on blast resistant windows is scarce in the literature. Therefore, a comprehensive research project was undertaken to address the behaviour, analysis, and design of window retention anchors. The research program consisted of combined experimental and analytical components. Three main phases were pursued, comprising of: i) Experimental research using a shock tube as blast simulator, ii) Numerical investigation based on three-dimensional finite element method (FEM) of analysis, and iii) Non-linear dynamic analysis of window systems based on a single-degree-of-freedom (SDOF) simplification. The experimental phase consisted of tests of 23 punched windows mounted on four different types of substrates consisting of structural steel, reinforced concrete, concrete block masonry, and stone masonry. The experimental parameters included window size and aspect ratio, glazing type, protective film thickness, substrate type, as well as the number and pattern of window retention anchors. Two levels of blast pressure-impulse combinations were used as per the recommendations of the U.S General Services Administration (GSA).The numerical phase involved FEM modelling and analysis of selected test windows. The FEM models were first validated against test results. The validated models were then employed to conduct an analytical parametric study. The parameters in this phase consisted of; substrate type, window frame rigidity, anchor fixity level in the substrate, window aspect ratio and size, anchor spacing, and blast pressure-impulse combination. The results demonstrated the significance of design parameters on window response, while also defining anchor force distribution along the window frame. A simplified SDOF method of analysis was developed for window systems, including the effects of anchor flexibility and substrate rigidity on non-linear response. The analysis approach includes the construction of window resistance functions in pre-break and post-break phases of response, where the latter stage of response is dominated by the membrane action of protective film. The analysis leads to the computation of anchor design forces, which have been validated against anchor shear and axial tension forces recorded experimentally. The SDOF analysis is recommended for use in designing blast-resistant window retention anchors on different substrates.

<div>Laser-absorption spectroscopy (LAS) is widely used for providing non-intrusive and quantitative measurements of gas properties (such as temperature and absorbing species mole fraction) in combustion environments. However, challenges may arise from the line-of-sight nature of LAS diagnostics, which can limit their spatial resolution. Further, time-resolution of such techniques as scanned direct-absorption or wavelength-modulation spectroscopy is limited by the scanning speed of the laser and the optical bandwidth is often limited by a combination of a laser's intrinsic tunability and its scanning speed. The work presented in this dissertation investigated how recent advancements in mid-IR camera technology and lasers can be leveraged to expand the spatial, temporal, and spectral measurement capabilities of LAS diagnostics. Novel laser-absorption imaging and ultrafast laser-absorption spectroscopy diagnostics are presented in this dissertation. In addition, the high-pressure combustion chamber (HPCC) and high-pressure shock tube (HPST) were designed and built to enable the study of, among others, energetic material combustion, spectroscopy, non-equilibrium and chemistry using optical diagnostics.<br></div><div><br></div>

Shock-tube experiments are typically performed at high temperatures (≥1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry of a reaction in a shock-tube experiment. Using mathematical models, analysis was performed studying the effects of temperature, pressure, shock-tube inner diameter, and test-port location at various test times (from 1 - 20 ms) on temperature maintenance. Three models, each more complex than the previous, were used to simulate test conditions in the endwall region behind the reflected shock wave with Ar and N2 as bath gases. Temperature profile, thermal BL thickness, and other parametric results are presented herein. It was observed that higher temperatures and lower pressures contributed to a thicker thermal boundary layer, as did shrinking inner diameter. Thus it was found that a test case such as 800K and 50 atm in a 16.2-cm-diameter shock tube in Argon maintained thermal integrity much better than other cases - pronounced by a thermal boundary layer ≤ 1 mm thick and an average temperature ≥ 799.9 K from 1-20 ms.

No description available.