Dissertations / Theses: 'Shock wave'

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Sanderson, Simon R. "Shock wave interaction in hypervelocity flow /." Web site:, 1995. http://etd.caltech.edu/etd/available/etd-11092004-094744/.

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Mutz, Andrew Howard Vreeland Thad. "Heterogeneous shock energy deposition in shock wave consolidation of metal powders /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06282007-091349.

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Fu, Y. "Propagation of weak shock waves in nonlinear solids." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384589.

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Lloyd, Alan. "Performance of reinforced concrete columns under shock tube induced shock wave loading." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28510.

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Recent events including deliberate attacks and accidental explosions have highlighted the need for greater research in structural response to blast loading. One of the primary research focuses has been on the prevention of progressive collapse of structures. The response of vertical load transferring members, such as columns, is of particular importance to progressive collapse prevention. In order to understand and predict the behaviour of the global structure during and after a blast loading event, a greater understanding of column behaviour must be developed. Currently there is a limited amount of experimental test data available on the response of reinforced concrete columns exposed to blast loads. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 14 half scale reinforced concrete columns were constructed and tested under blast pressures. The columns were designed according to Canadian Standard Association (CSA) Standard A23.3 for the "Design of Concrete Structures" (2006) standard as first story columns for both seismic and non-seismic regions. Axial load was applied to levels similar to what can be expected in actual structures. The columns were exposed to various pressure-impulse combinations which resulted in a range of column response. Comparisons are made between seismically designed and detailed columns and those that represent non-seismic gravity load columns in terms of displacement under similar shockwave loading. In addition, numerical analyses were conducted using single degree of freedom dynamic analysis. The numerical analysis accounts for the loss of axial load observed with horizontal displacement, strain rate effects on material strengths, the formation of plastic hinges in the column near the supports and at mid-height and the corresponding change in resistance and the response mode shape. The numerical analysis is validated with the experimental results and proven to accurately predict displacement of reinforced concrete columns under shock wave loading. The results indicate that an equivalent single degree of freedom model may be used to determine the response of a column under air blast induced shock loading if proper displacement-resistance models that account for material strength increase factors and change in axial load are used.

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Jamaluddin, Ahmad Riza. "Free-Lagrange simulations of shock-bubble interaction in extracorporeal shock wave lithotripsy." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/47507/.

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Sondén, Anders. "Shock wave effects on the vascular endothelium /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-183-7/.

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Crossley, Peter Simon. "On spectral methods for shock wave calculations." Thesis, Manchester Metropolitan University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361577.

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Touber, Emile. "Unsteadiness in shock-wave/boundary layer interactions." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/161073/.

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The need for better understanding of the low-frequency unsteadiness observed in shock wave/turbulent boundary layer interactions has been driving research in this area for several decades. This work investigates the interaction between an impinging oblique shock and a supersonic turbulent boundary layer via large-eddy simulations. Special care is taken at the inlet in order to avoid introducing artificial low-frequency modes that could affect the interaction. All simulations cover extensive integration times to allow for a spectral analysis at the low frequencies of interest. The simulations bring clear evidence of the existence of broadband and energetically-significant low-frequency oscillations in the vicinity of the reflected shock, thus confirming earlier experimental findings. Furthermore, these oscillations are found to persist even if the upstream boundary layer is deprived of long coherent structures. Starting from an exact form of the momentum integral equation and guided by data from large-eddy simulations, a stochastic ordinary differential equation for the reflectedshock foot low-frequency motions is derived. This model is applied to a wide range of input parameters. It is found that while the mean boundary-layer properties are important in controlling the interaction size, they do not contribute significantly to the dynamics. Moreover, the frequency of the most energetic fluctuations is shown to be a robust feature, in agreement with earlier experimental observations. Under some assumptions, the coupling between the shock and the boundary layer is mathematically equivalent to a first-order low-pass filter. Therefore, it is argued that the observed lowfrequency unsteadiness is not necessarily a property of the forcing, either from upstream or downstream of the shock, but simply an intrinsic property of the coupled dynamical system.

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Schilling, Mark Wesley. "Hydrodynamic Shock Wave Effects on Protein Functionality." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35132.

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USDA Select bovine Biceps femoris (BF) samples were divided into four sections and randomly assigned to three hydrodynamic shock wave (HSW) treatments and a control. Different amounts of explosive (105 g, H1; 200 g, H2; 305 g, H3) were suspended in the center of the hemishell tank, 26.7 cm above the vacuum packaged beef placed on the bottom center of that water-filled tank and detonated, representing three HSW treatments. In addition, BF steaks (2.54-cm thick) from a different and limited common source (2 muscles) were packaged with each HSW designated BF section. These served as internal refernce steaks (IRS) for the six replications to determine if the HSW treatments physically altered the structural integrity of the meat. H1 and H3 decreased (P<0.05) Warner-Bratzler shear values of the IRS from 3.86 and 3.99 kg (controls) to 3.01 and 3.02 kg (HSW), respectively. H2 shear values, 3.86 (control) to 3.46 kg (HSW) were not different (P> 0.05). HSW and control BF sections were analyzed for protein solubility and then used to manufacture frankfurters formulated with 2.0% NaCl, 0.5 % sodium tripolyphosphate, 156 ppm sodium nitrite, 0.42 % sodium erythorbate, 2.0 % sucrose, and 25 % water. Frankfurters (cooked to 71 C) were evaluated for cooking yield, CIE L*a*b*, nitrosylhemochrome, Texture Profile Analysis (hardness, cohesiveness), and stress and strain (torsion testing). Compared to the control samples, the HSW did not affect (P>0.05) myofibrillar or sarcoplasmic protein solubility, cooking yield, or color. Textural properties and gel strength of the frankfurters were not affected (P>0.05) by the HSW. These results indicate that beef trim obtained from HSW processed meat can be used interchangeably with normal meat trim in the production of further processed meats since the functionality of meat protein is not affected significantly by the HSW process. Master of Science

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Kessaratikoon, Prasong. "Shock wave dispersion in weakly ionized gas /." Connect to this resource. (Authorized users only), 2003.

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Montilla, Karina L. "Shock wave processing of transitional metal silicides." Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://resolver.caltech.edu/CaltechETD:etd-09202002-154801.

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Lokhandwalla, Murtuza Sturtevant Bradford. "Damage mechanisms in shock wave lithotripsy (SWL) /." Diss., Pasadena, Calif. : California Institute of Technology, 2001. http://resolver.caltech.edu/CaltechETD:etd-03162005-130412.

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Masse, Robert K. "Fluid dynamics of the shock wave reactor /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9961.

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Wolfrum, Bernhard. "Cavitation and shock wave effects on biological systems." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971895082.

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Dominy, Robert Gerald. "Rarefied hypersonic shock wave and blunt body flows." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47034.

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Lang, Ruitian. "Propagation of gravitons in the shock wave geometry." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51580.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. Includes bibliographical references (p. 51). In this thesis, I study propagation of gravitons in the shock wave geometry in the context of the AdS/CFT correspondence, with the goal to uncover some constraint on the supergravity action in the AdS space. In studying the shock wave geometry in an anti-deSitter (AdS) space, I find that the functional form of the shock wave metric does not receive a' correction, but the wave profile does. Then I study the propagation of gravitons in the shock wave geometry and show that the wave function has a finite jump at the shock wave frontier, and this corresponds to a shift in position of the graviton in the semi-classical picture. by Ruitian Lang. S.B.

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Pavlov, Atanas (Atanas Ivanov). "Needle-free drug delivery using shock wave techniques." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36245.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. "June 2006." Includes bibliographical references (leaves 93-94). A recent advancement in the area of needle-free injection systems has been the development of devices capable of epidermal delivery of powder medications. These devices use high-pressure compressed gas to accelerate drug particles 2 to 50 gpm in size to velocities of 200 to 1000 m/s. At these speeds the particles have sufficient momentum to penetrate the skin barrier and reach the viable epidermal layers. The devices offer much better control over the depth of penetration than traditional hypodermic needles, a factor particularly important in vaccine delivery. However they still have not found wide spread use, because of their cost. We studied the parameters determining the performance of these devices and used that knowledge to create a simple and reusable device capable of delivering 3 to 10 mg of powder formulation to the viable epidermis. Furthermore we showed that hydrogen-oxygen combustion could be used to create the shock wave required to accelerate the drug particles. This proves that portable reusable devices powered by hydrogen can be constructed and used for vaccine and medication delivery. by Atanas Pavlov. S.M.

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Nwokeoha, Sandra. "Lithotripter shock wave induced RNA-based gene therapy." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:89b67c7d-4b1c-4254-8e10-86a8e6c6c79d.

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Gene therapy is the process of introducing genes to augment or minimise the expression of absent or defective genes, respectively. Non-viral gene delivery systems for the treatment of genetic diseases, have evolved into highly appreciable nucleic acid-based therapies due to considerably less risk of host immunogenicity and induction of inflammatory responses. However, they are challenged by limited delivery. Thus, more efficient strategies are continually being sought. Lithotripter shock waves (LSW) are powerful acoustic waves that are an attractive choice of delivery system, as they offer a non-invasive, targeted and safe approach. Furthermore, the delivery of messenger ribonucleic acid (mRNA) possesses several advantages over commonly delivered plasmid deoxyribonucleic acids (pDNA), because it does not require opening of the nuclear envelope, thereby reducing the level of cell injury necessary for transfection. This work presents the first investigation on the efficacy of LSW mediated mRNA delivery, based on optimised SW parameters that balance the desired enhanced permeability of cell membranes against undesired cytotoxicity, and maintain the structural and biological stability of the RNA. A transfectability measure that defines the ability of SWs to permeabilise a cell whilst keeping it alive was established for dissimilar cell types, as a function of the acoustic pressure and number of SWs. Statistically significant RNA uptake was recorded in a tissue mimicking system, and using RNA analogues at various concentrations, the SW induced bio-distribution was characterised. In addition to LSW induced gene augmentation using mRNA, it was shown that LSWs could be used to effect gene inhibition through the delivery of siRNA. Kinetic experiments were carried out to measure mRNA uptake during shock wave exposure and indicated that rate of delivery was highest at the start of the SW dose and decreased during treatment. The results also suggested that the enhancement of cell permeability was significantly transient, and that mRNA was highly susceptible to degradation in its naked state. Furthermore, mRNA-based gene expression was shown to be predictive but quantal. The in vitro tissue model was improved from a gel-based system, to one that incorporated multi-cellular spheroids which capture aspects of 3-D tumours. Static overpressure was applied during SW exposure in order to suppress cavitation effects and isolate effects that could be attributed to shear due to cell-to-cell coupling. The results showed that mild overpressure improved RNA uptake the most, but that at higher overpressure, the level of increase in RNA uptake relative to controls, was dependent on the type of RNA nucleotide being delivered. This suggested that a complex interaction between LSW cavitation and direct stress dominates delivery. A final report was on the significant improvement of gene delivery when mRNA was encapsulated within a lipid nanoparticle vector, and SW exposure was assisted by cavitation agents. Also, by exposure to another acoustic stimulus - focused ultrasound (US), direct comparisons were made between SWs and US on the efficiency of delivery and tissue penetration. In conclusion, this thesis has shown that by choosing parameters appropriately, shock waves can be a promising strategy for the delivery of genes to cells.

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Meek, Kimberly I. "Hydrodynamic Shock Wave: Decreasing Broiler Breast Aging Time." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36505.

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The Hydrodyne process was used to tenderize early de-boned broiler (EB) breasts. The first objective was to determine effects of explosive and distance of the explosive to the meat surface. EB breasts were removed immediately after initial chill (45 min post-mortem), stored for 24 hours, and subjected to one of four treatment combinations. Hydrodyne treatment of 350 g at 20 cm produced the greatest increase in Warner-Bratzler shear (1.9-cm wide strips) tenderness (28.3%), and was the only treatment to increase tenderness (peak force 4.3 kg) to a level equivalent (P>0.05) to aged controls (CA; peak force 3.1 kg). The second objective was to determine quality (tenderness, purge loss, cooking loss, and color) and sensory characteristics of Hydrodyne treated (HYD) broiler breasts. Initial pH values for CA (5.86) and EB (5.71) breasts were different (P<0.05). Warner-Bratzler and Lee-Kramer shear values (1.0-cm wide and thick strips) for CA (1.56 kg; 6.0 kg*mm/g, respectively) were different from HYD (3.7 kg; 11.0 kg*mm/g, respectively) and EB breasts (4.7 kg; 12.1 kg*mm/g, respectively). CA resulted in more tender, flavorful, and juicer breasts than HYD and EB. HYD was lower in initial moisture release than EB. EB breasts with significant tenderness problems can be tenderized by the Hydrodyne process based on instrumental shear results. However, higher levels of explosive may be required to optimize tenderness improvement of breasts that vary significantly in initial tenderness. Incorporation of this technology, once optimized, on an industry production level would benefit poultry processors in reducing or eliminating broiler breast aging. Master of Science

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Teitz, Emilie Maria. "Characterization of the Shock Wave Structure in Water." Thesis, Marquette University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10267152.

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The scientific community is interested in furthering the understanding of shock wave structures in water, given its implications in a wide range of applications; from researching how shock waves penetrate unwanted body tissues to studying how humans respond to blast waves. Shock wave research on water has existed for over five decades. Previous studies have investigated the shock response of water at pressures ranging from 1 to 70 GPa using flyer plate experiments. This report differs from previously published experiments in that the water was loaded to shock pressures ranging from 0.36 to 0.70 GPa. The experiment also utilized tap water rather than distilled water as the test sample. Flyer plate experiments were conducted in the Shock Physics Laboratory at Marquette University to determine the structure of shock waves within water. A 12.7 mm bore gas gun fired a projectile made of copper, PMMA, or aluminum at a stationary target filled with tap water. Graphite break pins in a circuit determined the initial projectile velocity prior to coming into contact with the target. A Piezoelectric timing pin (PZT pin) at the front surface of the water sample determined the arrival of the leading wave and a Photon Doppler Velocimeter (PDV) measured particle velocity from the rear surface of the water sample. The experimental results were compared to simulated data from a Eulerian Hydrocode called CTH [1]. The experimental results differed from the simulated results with deviations believed to be from experimental equipment malfunctions. The main hypothesis being that the PZT pin false triggered, resulting in measured lower than expected shock velocities. The simulated results were compared to published data from various authors and was within range.

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Boey, Chung Wai. "Investigation of shock wave attenuation in porous materials." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FBoey.pdf.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2009. Thesis Advisor(s): Hixson, Robert S. Second Reader: McNelley, Terry. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: Porous foams, dynamic compaction, multi-layered armor, ballistic performance, shock wave attenuation. Includes bibliographical references (p. 89-90). Also available in print.

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Nelsen, Cory. "Multiscale modeling and simulation of shock wave propagation." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2591.

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Multiscale modeling and simulation has been a growing interest for researchers as computational power and speed has increased. Multiscale models allow for the study of different size scales, which may be governed by different sets of physical laws. Typically, the homogenization between the different scales is done at a zero temperature. The main goal of this thesis is to develop and conduct multiscale modeling and simulation of shock wave propagation with the removal of numerical errors and inclusion of temperature effects.

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Burrell, Russell P. "Performance of Steel Fibre Reinforced Concrete Columns under Shock Tube Induced Shock Wave Loading." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23516.

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It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete. The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.

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Fox, Thomas Edward. "Strong shock wave generation by fast electron energy deposition in shock ignition relevant plasmas." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/6625/.

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The potential role of fast electrons is one of the major unknowns in shock ignition inertial con- finement fusion. Of particular interest is the possibility that they may play a beneficial role in the generation of the ignitor shock by contributing to the ablation pressure. Here, some of the fundamental relations governing fast electron driven shock wave generation in dense plasmas are determined. To that end, a 1D planar hybrid model of fast electron transport through dense plasmas is presented. It is found that, using quasi-realistic electron populations, it is possible to generate shock waves with peak pressures that agree with a simple scaling law and have sustained shock pressures of several hundred Mbars. However, the spatial and temporal scales required for shock waves to fully develop increase with fast electron temperature and can become significant. Careful consideration of this effect is needed when assessing their usefulness as shock wave drivers. A characteristic time of shock wave formation is reinterpreted as the definitive time taken for a localised source of internal energy in an otherwise uniform fluid to drive a blast wave containing its maximum kinetic energy. This relation is of utility in inertial confinement fusion where ignition relies on the conversion of kinetic energy to internal energy at implosion stagnation. However, it is not straightforwardly reproducible by fast electron heating, which highlights the difficulties that may be encountered if fine control over shock wave formation is required. The shape of the density profile seems to be of secondary importance when compared with the consequences of heating using hotter electron populations. When heating times are on the time scale of the ignitor pulse, the density profile affects the efficiency of shock wave formation by determining the transition from an explosive regime to a driven regime of shock wave forma- tion. However, the time taken for the shock wave to contain its maximum kinetic energy is not significantly affected. It is shown that an externally applied magnetic field can constrain the range of fast electrons in solid density planar plastic targets, and enhance localised energy deposition. This mitigates the need for significant spatial and temporal scales when using fast electron populations with extended energy distributions to drive shock waves. However, this comes at the expense of the strength of the shock wave.

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Armstrong, Jonathan. "Design of a Free Field Blast Simulating Shock Tube." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32241.

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A 30.5 cm diameter, detonation driven shock tube facility has been designed, constructed and tested. The design goals of the shock tube were to reproduce free field blast wave profiles on a laboratory scale using atmospheric gaseous detonation as the energy source. Numerical simulations were utilized to explore the gas dynamic evolution inside detonation driven shock tubes and to select the optimal design parameters for the shock tube.The Friedlander profile was used to evaluate the generated pressure profiles as an approximation of free field blast waves. It has been found that the detonation driver length should be kept below 20% of the total length of the tube in order to produce Friedlander waves. Additionally, it has been found that an annular vent can be added to the shock tube to enhance the negative phase of the blast profile, more accurately reproducing real free field blast waves. The shock tube has been constructed in a modular fashion from 2.54 cm thick steel tubing. An adjustable bag type diaphragm has been employed to allow for a variable driver size and a high voltage ignition system is used to initiate detonation in the driver section. Due to the available location for the shock tube, tests using the vented configuration could not be accomplished for safety reasons. Conducted experiments produced results that agree well with corresponding numerical simulations. Overall, the shock tube design was successful in creating Friedlander blast waves. At the time of writing, a manufacturer error in correctly reporting the specifications of the clamps used on the shock tube resulted in a lower maximum pressure of operation.

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Brahmi, Nassim. "Etude numérique de la propagation et l’atténuation des ondes de choc en milieux confinés Turbulent structures of shock-wave diffraction over 90° convex corner Analysis of shock-wave diffraction over double concave cylindrical wedges. Part I: Shock dynamics Analysis of shock-wave diffraction over double cylindrical wedges. Part II: Vorticity generation Achieving an optimal shock-wave mitigation inside open channels with cavities for weak shock waves: a computational study." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR09.

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La propagation des ondes de choc implique des interactions complexes entre ondes et milieux environnants, ce qui engendre plusieurs phénomènes tels que la réflexion, la diffraction, etc. Pour clarifier davantage la physique associée à ces phénomènes, des simulations numériques hautes résolutions ont été réalisées. En particulier l'analyse de la diffraction des ondes de choc sur deux surfaces concaves cylindriques a révélé que les angles de transition, d'une réflexion régulière à une réflexion de Mach, augmentent avec le nombre de Mach, alors qu'ils sont presque égaux sur les deux surfaces concaves pour les régimes de Mach transsoniques et relativement plus important sur la deuxième surface pour les nombres de Mach plus élevés. Ceci prouve que l'écoulement est en mesure de conserver l'historique des événements passés sur l'ensemble du processus pour des nombres de Mach élevés. L'analyse de l'équation de transport de vorticité a montré, pour la première fois, que la diffusion de la vorticité due aux effets visqueux est assez importante par rapport au terme baroclinic pour les faibles nombres de Mach, alors que cette tendance est inversée pour les nombres de Mach les plus élevés. L'étude a également montré que le stretching de la vorticité dû aux effets de compressibilité joue un rôle important dans la production de vorticité. A la base de ces simulations numériques, une relation universelle a été proposée, permettant de prédire la trajectoire et la vitesse de l'onde incidente en fonction du nombre de Mach incident, du rayon de courbure de la géométrie et des propriétés du gaz. Par la suite, l'étude de la propagation des ondes de choc et leur atténuation dans des conduites de différentes hauteurs et présentant des cavités circulaires creuses de différentes profondeurs a été effectuée. Les résultats ont montré l'importance de la réduction de la hauteur du canal et le changement de la position de la section réduite en plus de l'angle de diffraction et de la profondeur de la cavité pour une meilleure atténuation des ondes. Un arrangement optimal de la position/hauteur du canal et de l'emplacement / profondeur de la cavité a été trouvé The propagation of shock waves involves complex interactions between waves and surrounding media, which gives rise to several phenomena such as reflection, diffraction, etc. To shed more light into the fundamental physics associated with these phenomena, high resolution numerical simulations were carried out. In particular, analysis of shock diffraction over double concave cylindrical wedges revealed that the transition angles, from regular to Mach reflection, increase with the Mach number, whereas they are found to be almost the same over the two concave surfaces for the transonic Mach regimes and relatively larger on the second surface for high ones showing that the flow is capable of retaining the memory of the past events over the entire process for the high Mach numbers. The analysis of the vorticity equation balance showed, for the first time, that the diffusion of the vorticity due to the viscous effects is quite important compared to the baroclinic term for low Mach numbers, while this trend is inverted for higher Mach numbers. The study also showed that the stretching of the vorticity due to the compressibility effects plays an important role in the vorticity production. On the basis of these numerical simulations, an approximate universal relation is proposed, allowing to predict the incident-shock trajectory and velocity as a function of the incident-shock Mach number, the radius of curvature of the geometry, and the gas properties. Afterward, the study of shock-waves propagation and their attenuation in channel flow having different heights and exhibiting a hollow circular cavities with different depths has been clone. The results also showed the importance of reducing the height of the channel and changing the position of the reduced section in addition to the diffraction angle and the cavity depth for better shock-waves attenuation. A subtle arrangement of channel position/height and a cavity location/depht was found

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OHSAWA, YUKIHARU, K. KATO, and H. HASEGAWA. "Simulation studies of positron acceleration by a shock wave." Cambridge University Press, 2006. http://hdl.handle.net/2237/10301.

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Collie, Jeffery C. "Unsteady shock wave effects on transonic turbine cascade performance." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040404/.

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Badr, Mohammad Ali. "Shock wave turbulent boundary layer interaction over a protrusion." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3942.

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This research attempts to investigate an important and common phenomenon in aerodynamics called shock interaction in a turbulent flow’s boundary layer. Due to advancements in current computational units, more complex geometries could be simulated with providing more accurate results. The tools used in this investigation are computational turbulent model of hybrid RANS/LES, called detached eddy simulation (DES). DES and its variant delayed detached eddy simulation (DDES) were the two computational schemes used for numerical simulation. Two protrusions were focused on in this work: a symmetrical bump and a proposed aircraft UHF antenna. Computation where performed with commercial software Cobalt and FLUENT in the High Performance Computing Center (HiPeCC) in Wichita State University. Computational simulation is costly in terms of energy consumption and time usage. Even so with the advanced computational units of HiPeCC, using in average of 18 processors, total simulation for this research took over 2 months of simulation. Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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Bessho, Naoki, and Yukiharu Ohsawa. "Electron acceleration and trapping by an oblique shock wave." American Institute of Physics, 2002. http://hdl.handle.net/2237/7093.

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Gibson, Thomas Mark. "The passive control of shock-wave/boundary-layer interactions." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/272691.

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Alamri, Sagr Mubarak. "SHOCK MITIGATION AND WAVE CONTROL USING ELASTIC METAMATERIAL STRUCTURES." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron154177943169993.

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Gongora, Orozco Nalleli. "Experimental studies on internal shock wave phenomena and interactions." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/experimental-studies-on-internal-shock-wave-phenomena-and-interactions(6325f185-76a1-483a-9d14-606a6a48374e).html.

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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.

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40

Tanguay, Michel Colonius Timothy E. "Computation of bubbly cavitating flow in shock wave lithotripsy /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-05282004-130028.

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41

Grossman, Ilan Jesse. "Effect of confinement on shock wave-boundary layer interactions." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/47924.

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Shock wave-boundary layer interactions (SWBLIs) are an inevitable feature of compressible flow and can have a large detrimental effect on the performance of aerodynamic applications. To address and design to accommodate them, requires detailed understanding of the underlying flow mechanisms. At present, our knowledge of these mechanisms is insufficient to accurately predict SWBLI behavior. This experimental study attempts to provide a better understanding of some of these mechanisms by focusing on the three- dimensionality inherent in oblique SWBLIs. The test configuration consists of an oblique shock wave in Mach 2 flow in a rectangular test section at flow deflection angles of 8° , 10° , and 12°. The key parameters of test section effective aspect ratio (AReff) and shock generator geometry are varied to assess their ability to amplify/attenuate the three-dimensionality of a nominally two-dimensional SWBLI. An innovative traversable shock generator with interchangeable wedge geometries allow the effects of AReff , expansion fan placement, and side-wall gap to be studied. The flow is investigated by employing Schlieren photography, surface flow visualization, static pressure measurements, Laser Doppler Anemometry and Particle Image Velocimetry. It is observed that with an increase in AReff, or a downstream movement of the expansion fan, or a decrease in side-wall gap, the SWBLI and shock-induced separation will grow. The growth of the separated region exhibits an increase in three-dimensionality and at high AReff the regular reflection is observed to evolve into a Mach reflection without an increase in incident shock strength. Models are proposed to explain the observed behavior as a function of separation growth and a reduction of the influence of free interaction theory.

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42

Kracht, Jonathan M. "Trading kidney stones with sound during shock wave lithotripsy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12800.

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Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. The prevalence of kidney stones has increased significantly over the past decades. One of the primary treatments for kidney stones is shock wave lithotripsy which focuses acoustic shock waves onto the stone in order to fragment it into pieces that are small enough to pass naturally. This typically requires a few thousand shock waves delivered at a rate of about 2 Hz. Although lithotripsy is the only non-invasive treatment option for kidney stones, both acute and chronic complications have been identified which could be reduced if fewer shock waves were used. One factor that could be used to reduce the number of shock waves is accounting for the motion of the stone which causes a portion of the delivered shock waves to miss the stone, yielding no therapeutic benefit. Therefore identifying when the stone is not in focus would allow tissue to be spared without affecting fragmentation. The goal of this thesis is to investigate acoustic methods to track the stone in real-time during lithotripsy in order to minimize poorly-targeted shock waves. A relatively small number of low frequency ultrasound transducers were used in pulse-echo mode and a novel optimization routine based on time-of-flight triangulation is used to determine stone location. It was shown that the accuracy of the localization may be estimated without knowing the true stone location. This method performed well in preliminary experiments but the inclusion of tissue-like aberrating layers reduced the accuracy ofthe localization. Therefore a hybrid imaging technique employing DORT (Decomposition of the Time Reversal Operator) and the MUSIC (Multiple Signal Classification) algorithm was developed. This method was able to localize kidney stones to within a few millimeters even in the presence of an aberrating layer. This would be sufficient accuracy for targeting lithotripter shock waves. The conclusion of this work is that tracking kidney stones with low frequency ultrasound should be effective clinically.

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43

Ben, Hassan Saïdi Ismaïl. "Numerical simulations of the shock wave-boundary layer interactions." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS390/document.

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Les situations dans lesquelles une onde de choc interagit avec une couche limite sont nombreuses dans les industries aéronautiques et spatiales. Sous certaines conditions (nombre de Mach élevé, grand angle de choc…), ces interactions entrainent un décollement de la couche limite. Des études antérieures ont montré que la zone de recirculation et le choc réfléchi sont tous deux soumis à un mouvement d'oscillation longitudinale à basse fréquence connu sous le nom d’instabilité de l’interaction onde de choc / couche limite (IOCCL). Ce phénomène appelé soumet les structures à des chargement oscillants à basse fréquence qui peuvent endommager les structures.L’objectif du travail de thèse est de réaliser des simulations instationnaires de l’IOCCL afin de contribuer à une meilleure compréhension de l’instabilité de l’IOCCL et des mécanismes physiques sous-jacents.Pour effectuer cette étude, une approche numérique originale est utilisée. Un schéma « One step » volume fini qui couple l’espace et le temps, repose sur une discrétisation des flux convectifs par le schéma OSMP développé jusqu’à l’ordre 7 en temps et en espace. Les flux visqueux sont discrétisés en utilisant un schéma aux différences finies centré standard. Une contrainte de préservation de la monotonie (MP) est utilisée pour la capture de choc. La validation de cette approche démontre sa capacité à calculer les écoulements turbulents et la grande efficacité de la procédure MP pour capturer les ondes de choc sans dégrader la solution pour un surcoût négligeable. Il est également montré que l’ordre le plus élevé du schéma OSMP testé représente le meilleur compromis précision / temps de calcul. De plus un ordre de discrétisation des flux visqueux supérieur à 2 semble avoir une influence négligeable sur la solution pour les nombres de Reynolds relativement élevés considérés.En simulant un cas d’IOCCL 3D avec une couche limite incidente laminaire, l’influence des structures turbulentes de la couche limite sur l’instabilité de l’IOCCL est supprimée. Dans ce cas, l’unique cause d’IOCCL suspectée est liée à la dynamique de la zone de recirculation. Les résultats montrent que seul le choc de rattachement oscille aux fréquences caractéristiques de la respiration basse fréquence du bulbe de recirculation. Le point de séparation ainsi que le choc réfléchi ont une position fixe. Cela montre que dans cette configuration, l’instabilité de l’IOCCL n’a pas été reproduite.Afin de reproduire l’instabilité de l’IOCCL, la simulation de l’interaction entre une onde de choc et une couche limite turbulente est réalisée. Une méthode de turbulence synthétique (Synthetic Eddy Method - SEM) est développée et utilisée à l’entrée du domaine de calcul pour initier une couche limite turbulente à moindre coût. L’analyse des résultats est effectuée en utilisant notamment la méthode snapshot-POD (Proper Orthogonal Decomposition). Pour cette simulation, l’instabilité de l’IOCCL a été reproduite. Les résultats suggèrent que la dynamique du bulbe de recirculation est dominée par une respiration à moyenne fréquence. Ces cycles successifs de remplissage / vidange de la zone séparée sont irréguliers dans le temps avec une taille maximale du bulbe de recirculation variant d’un cycle à l’autre. Ce comportement du bulbe de recirculation traduit une modulation basse fréquence des amplitudes des oscillations des points de séparation et de recollement et donc une respiration basse fréquence de la zone séparée. Ces résultats suggèrent que l’instabilité de l’IOCCL est liée à cette dynamique basse fréquence du bulbe de recirculation, les oscillations du pied du choc réfléchi étant en phase avec le point de séparation Situations where an incident shock wave impinges upon a boundary layer are common in the aeronautical and spatial industries. Under certain circumstances (High Mach number, large shock angle...), the interaction between an incident shock wave and a boundary layer may create an unsteady separation bubble. This bubble, as well as the subsequent reflected shock wave, are known to oscillate in a low-frequency streamwise motion. This phenomenon, called the unsteadiness of the shock wave boundary layer interaction (SWBLI), subjects structures to oscillating loads that can lead to damages for the solid structure integrity.The aim of the present work is the unsteady numerical simulation of (SWBLI) in order to contribute to a better understanding of the SWBLI unsteadiness and the physical mechanism causing these low frequency oscillations of the interaction zone.To perform this study, an original numerical approach is used. The one step Finite Volume approach relies on the discretization of the convective fluxes of the Navier Stokes equations using the OSMP scheme developed up to the 7-th order both in space and time, the viscous fluxes being discretized using a standard centered Finite-Difference scheme. A Monotonicity-Preserving (MP) constraint is employed as a shock capturing procedure. The validation of this approach demonstrates the correct accuracy of the OSMP scheme to predict turbulent features and the great efficiency of the MP procedure to capture discontinuities without spoiling the solution and with an almost negligible additional cost. It is also shown that the use of the highest order tested of the OSMP scheme is relevant in term of simulation time and accuracy compromise. Moreover, an order of accuracy higher than 2-nd order for approximating the diffusive fluxes seems to have a negligible influence on the solution for such relatively high Reynolds numbers.By simulating the 3D unsteady interaction between a laminar boundary layer and an incident shock wave, we suppress the suspected influence of the large turbulent structures of the boundary layer on the SWBLI unsteadiness, the only remaining suspected cause of unsteadiness being the dynamics of the separation bubble. Results show that only the reattachment point oscillates at low frequencies characteristic of the breathing of the separation bubble. The separation point of the recirculation bubble and the foot of the reflected shock wave have a fixed location along the flat plate with respect to time. It shows that, in this configuration, the SWBLI unsteadiness is not observed.In order to reproduce and analyse the SWBLI unsteadiness, the simulation of a shock wave turbulent boundary layer interaction (SWTBLI) is performed. A Synthetic Eddy Method (SEM), adapted to compressible flows, has been developed and used at the inlet of the simulation domain for initiating the turbulent boundary layer without prohibitive additional computational costs. Analyses of the results are performed using, among others, the snapshot Proper Orthogonal Decomposition (POD) technique. For this simulation, the SWBLI unsteadiness has been observed. Results suggest that the dominant flapping mode of the recirculation bubble occurs at medium frequency. These cycles of successive enlargement and shrinkage of the separated zone are shown to be irregular in time, the maximum size of the recirculation bubble being submitted to discrepancies between successive cycles. This behaviour of the separation bubble is responsible for a low frequency temporal modulation of the amplitude of the separation and reattachment point motions and thus for the low frequency breathing of the separation bubble. These results tend to suggest that the SWBLI unsteadiness is related to this low frequency dynamics of the recirculation bubble; the oscillations of the reflected shocks foot being in phase with the motion of the separation point

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44

Cachucho, André Rodrigues. "Weak shock wave reflections due to transverse waves in a conventional shock tube." Thesis, 2012. http://hdl.handle.net/10539/11234.

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Previous experimental work, utilising a unique large scale shock tube, showed that the four-wave shock reflection pattern, known as the Guderley reflection existed for Mach numbers below 1.10 on wedge angles of 10° and 15°. The current study proves for the first time that these rare reflections can be produced in a conventional shock tube for Mach numbers ranging from 1.10 to 1.40 and for various disturbances in the flow. Two shock tube configurations were tested, the first consisted of a perturbation source on the floor of the tube, and the second utilised a variable diverging section (10°, 15°, and 20°). A new principle was applied where the developed Mach reflection undergoes successive reflections off the upper and lower walls of a tube to produce the desired reflection. The high resolution images captured using a sensitive schlieren system showed evidence of the fourth wave, namely the expansion fan, for the majority of the results for both shock tube configurations. A shocklet terminating the supersonic patch behind the reflected wave was interestingly only observed for Mach numbers of approximately 1.20. The wave structures were similar to those observed in previous experimental work, except no evidence of the second shocklet nor the multi-patch geometry was found. Multi-exposure images of the propagating shock superimposed on a single image frame, analysed with oblique shock equations, estimated the velocities near the triple point. It was shown that the reflected wave is very weak, and that the flow behind the Mach stem is supersonic confirming the shock reflections to be indeed Guderley reflections.

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45

Cates, Joseph Eugene. "Studies of shock wave focusing using geometrical shock dynamics." Thesis, 1996. https://thesis.library.caltech.edu/3921/1/Cates_je_1996.pdf.

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A finite-difference numerical method for geometrical shock dynamics has been developed, based on the analogy between the equations and the supersonic potential equation. The method has proven to be a valuable tool for analyzing the complex nonlinear processes that occur in shock focusing. The approximate shock dynamics theory is able to capture the effects of initial Mach number and aperture angle on the focal region. The numerical results duplicate the strong, moderate, and weak shock behaviors observed in experiments, with good agreement for focal pressure and triple-point path. The primary error arises due to the inability of shock dynamics to allow regular reflection along the centerline. Adequate resolution of the focal region proves to be particularly important to properly judge the accuracy of the shock dynamics solution. The appropriate shock dynamics equations are developed for the case of shock propagation into a nonuniform media for a general equation of state with nonuniform freestream velocity. The modification of the numerical method to this more general problem is straightforward. The complete shock dynamics equations are derived for both perfect gas and water using the modified Tait equation. The results for propagation of a planar shock over cylindrical gas inhomogeneities shows excellent agreement with experimental results. The propagation of sonic booms through the atmosphere provides examples of all major types of weak shock behavior. The extensive seismic network in Southern California, consisting of over two hundred sites covering over 50,000 square kilometers, is used to map primary and secondary sonic boom carpets. The results show sonic boom ground exposure under the real atmosphere is much larger than previously expected.

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46

Naidoo, Kavendra. "Dynamic shock wave reflection phenomena." Thesis, 2011. http://hdl.handle.net/10539/10527.

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There have been numerous studies on the steady state transition criteria between regular reflection (RR) and Mach reflection (MR) of shock waves for a stationary, two-dimensional (2D) wedge in a steady supersonic free stream since the original shock wave reflection research by Ernst Mach in 1878. The steady, 2D transition criteria between RR and MR are well established. There has been little done to consider the dynamic effect of rapid wedge rotation on RR $ MR transition. This thesis presents the results of an investigation of the effect of rapid wedge rotation on transition between 2D regular and Mach reflection in the weak and strong-reflection ranges, with experiment and com- putational fluid dynamics. A novel facility was designed to rotate a pair of large aspect ratio wedges in a 450 mm × 450 mm supersonic wind tunnel at wedge rotation speeds up to 11000 deg/s resulting in wedge tip speeds approximately 3.3 % of the free stream acoustic speed. Steady state, baseline experiments, in which the wedges were rotated very gradually, were also completed. High-speed images and measurements are pre- sented for the steady and dynamic experiments. Numerical solution of the inviscid governing flow equations was used to model the steady case and to mimic the experimental motion in the dynamic experiments. The two-dimensional, Euler CFD code was developed at the University of the Witwatersrand. Steady state experiments were completed in the weak and strong-reflection ranges and transition measure- ments were compared to 2D steady, theoretical values and Euler computations. There was close agreement between theoretical, computational and experimental transition for the steady case, with the following ex- ception. Due to the levels of free stream noise in the supersonic wind tunnel, incidence-induced hysteresis was not observed in the strong-reflection region and transition occurred at the von Neumann condition for increasing and decreasing incidence. In the ideal case, RR ! MR transition occurs at the detachment condition and the reverse transition occurs at the von Neumann condition. Therefore, there is discrepancy between steady theory/CFD and experiment for RR ! MR transition in the strong-reflection range only, which is consistent with observations in other facilities with sufficient levels of free stream noise. Dynamic RR ! MR Transition : Rapid wedge rotation did generate a measurable dynamic effect on RR ! MR transition. This thesis presents the first experimental evidence of RR ! MR reflection transition beyond the steady detachment condition in the weak and strong-reflection ranges. In all instances, there was good agreement between experiment and 2D CFD, including dynamic RR ! MR transition in the strong-reflection region. The agreement between the experiment, in which small perturbations are always present in the free stream, and the CFD, in which the free stream is without perturbations, implies that RR ! MR transition in the strong-reflection region becomes insensitive to free stream noise above a certain critical rotation speed. Due to the close agreement between CFD and experiment, the Euler code was also applied to scenarios beyond the limits of the current facility to explore the influence of variables in the parameter space, viz. rotation speed, initial incidence and rotation centre. CFD was also used to investigate the dynamic transition mechanism over a limited number of simulations. For dynamic RR ! MR transition, a distinction is drawn between the sonic, length scale and detachment conditions. The point at which the flow downstream of the reflection point goes sonic is not necessarily the point at which the wedge length scale, from the wedge trailing edge expansion, is communicated to the reflection point. There is evidence to support that the RR ! MR transition criteria for the rapidly rotating wedge is neither the sonic or length scale conditions, but rather the condition at which the reflected wave can no longer satisfy the boundary condition at the reflection point. Dynamic simulations showed that RR could be maintained with a length scale present at the reflection point. Other dynamic simulations showed, for the first time, that transition to MR was possible without the wedge length scale being communicated to the reflection point. Dynamic MR ! RR transition : Rapid wedge rotation generated a measurable effect on MR ! RR transition. The first experimental evidence of MR ! RR transition below the steady von Neumann condition is presented. Once again, there was good agreement between experiment and 2D CFD. CFD was used to investigate the sensitivity of transition to rotation speed, initial incidence and rotation centre in the strong and weak-reflection ranges. Due to impulsive wedge start and rapid wedge rotation, there are very marked dynamic effects on the variation of Mach stem height with wedge incidence and the deviation from the steady transition conditions is significant. The MR ! RR transition was found to be dependent on the initial condition and the transient variation of Mach stem height with wedge incidence.

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47

Khatta, Abhishek. "Experimental Studies on Shock-Shock Interactions in Hypersonic Shock Tunnels." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2927.

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Shock-shock interactions are among the most basic gas-dynamic problem, and are almost unavoidable in any high speed light, where shock waves generating from different sources crosses each other paths. These interactions when present very close to the solid surface lead to very high pressure and thermal loads on the surface. The related practical problem is that experienced at the cowl lip of a scramjet engine, where the interfering shock waves leads to high heat transfer rates which may also lead to the damage of the material. The classification by Edney (1968) on the shock-shock interaction patterns based on the visualization has since then served the basis for such studies. Though the problem of high heating on the surface in the vicinity of the shock-shock interactions has been studied at length at supersonic Mach numbers, the study on the topic at the hypersonic Mach numbers is little sparse. Even in the studies at hypersonic Mach numbers, the high speeds are not simulated, which is the measure of the kinetic energy of the ow. Very few experimental studies have addressed this problem by simulating the energy content of the ow. Also, some of the numerical studies on the shock-shock interactions suggest the presence of unsteadiness in the shock-shock interaction patterns as observed by Edney (1968), though this observation is not made very clearly in the experimental studies undertaken so far. In the present study, experiments are carried out in a conventional shock tunnel at Mach number of 5.62 (total enthalpy of 1.07 MJ/kg; freestream velocity of 1361 m/s), with the objective of mapping the surface pressure distribution and surface convective heat transfer rate distribution on the hemispherical body in the presence of the shock-shock interactions. A shock generator which is basically a wedge of angle = 25 , is placed at some dis-dance in front of the hemispherical body such that the planar oblique shock wave from the shock generator hits the bow shock wave in front of the hemi-spherical body. The relative distance between the wedge tip and the nose of the hemispherical body is allowed to change in di erent experiments to capture the whole realm of shock-shock interaction by making the planar oblique shock wave interact with the bow shock wave at different locations along its trajectory. The study results in a bulk of data for the surface pressure and heat transfer rates which were obtained by placing 5 kulites pressure transducers, 1 PCB pressure transducer and 21 platinum thin lm gauges along the surface of the hemispherical body in a plane normal to the freestream velocity direction. Along with the measurement of the surface pressure and the surface heat transfer rates, the schlieren visualization is carried out to capture the shock waves, expansion fans, slip lines, present in a certain shock-shock interaction pattern and the measured values were correlated with the captured schlieren images to evaluate the ow build up and steady and useful test time thereby helping in understanding the ow physics in the presence of the shock-shock interactions. From the present study it has been observed that in the presence of Edney Type-I and Edney Type-II interaction, the heat transfer rates on the hemi-spherical body are symmetrical about the centerline of the body, with the peak heating at the centerline which drops towards the shoulder. For Edney Type-III, Edney Type-IV, Edney Type-V and Edney Type-VI interaction pattern, the distribution in not symmetrical and shifts in peak heat transfer rates being on the side of the hemispherical from which planar oblique shock wave is incident. Also, it is observed that for the interactions which appear within the sonic circle, Edney Type-III and Edney Type-IV, the heat transfer rates observe an unsteadiness, such that the gauges located close to the interaction region experiencing varying heat transfer rates during the useful test time of the shock tunnel. Few experiments were conducted at Mach 8.36 (total enthalpy of 1.29 MJ/kg; freestream velocity of 1555.25 m/s) and Mach 10.14 (total enthalpy of 2.67 MJ/kg; freestream velocity of 2258.51 m/s) for the con gurations representing Edney Type-III interaction pattern to further evaluate the unsteady nature observed at Mach 5.62 ows. The unsteadiness was evident in both the cases. It is realized that the short test times in the shock tunnels pose a constraint in the study of unsteady flow fields, and the use of tailored mode operation of shock tunnel can alleviate this constraint. Also, limited number of experiments in the present study, which are carried out in a Free Piston Shock Tunnel, helps to understand the need to conduct such study in high enthalpy test conditions.

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48

Khatta, Abhishek. "Experimental Studies on Shock-Shock Interactions in Hypersonic Shock Tunnels." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2927.

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Shock-shock interactions are among the most basic gas-dynamic problem, and are almost unavoidable in any high speed light, where shock waves generating from different sources crosses each other paths. These interactions when present very close to the solid surface lead to very high pressure and thermal loads on the surface. The related practical problem is that experienced at the cowl lip of a scramjet engine, where the interfering shock waves leads to high heat transfer rates which may also lead to the damage of the material. The classification by Edney (1968) on the shock-shock interaction patterns based on the visualization has since then served the basis for such studies. Though the problem of high heating on the surface in the vicinity of the shock-shock interactions has been studied at length at supersonic Mach numbers, the study on the topic at the hypersonic Mach numbers is little sparse. Even in the studies at hypersonic Mach numbers, the high speeds are not simulated, which is the measure of the kinetic energy of the ow. Very few experimental studies have addressed this problem by simulating the energy content of the ow. Also, some of the numerical studies on the shock-shock interactions suggest the presence of unsteadiness in the shock-shock interaction patterns as observed by Edney (1968), though this observation is not made very clearly in the experimental studies undertaken so far. In the present study, experiments are carried out in a conventional shock tunnel at Mach number of 5.62 (total enthalpy of 1.07 MJ/kg; freestream velocity of 1361 m/s), with the objective of mapping the surface pressure distribution and surface convective heat transfer rate distribution on the hemispherical body in the presence of the shock-shock interactions. A shock generator which is basically a wedge of angle = 25 , is placed at some dis-dance in front of the hemispherical body such that the planar oblique shock wave from the shock generator hits the bow shock wave in front of the hemi-spherical body. The relative distance between the wedge tip and the nose of the hemispherical body is allowed to change in di erent experiments to capture the whole realm of shock-shock interaction by making the planar oblique shock wave interact with the bow shock wave at different locations along its trajectory. The study results in a bulk of data for the surface pressure and heat transfer rates which were obtained by placing 5 kulites pressure transducers, 1 PCB pressure transducer and 21 platinum thin lm gauges along the surface of the hemispherical body in a plane normal to the freestream velocity direction. Along with the measurement of the surface pressure and the surface heat transfer rates, the schlieren visualization is carried out to capture the shock waves, expansion fans, slip lines, present in a certain shock-shock interaction pattern and the measured values were correlated with the captured schlieren images to evaluate the ow build up and steady and useful test time thereby helping in understanding the ow physics in the presence of the shock-shock interactions. From the present study it has been observed that in the presence of Edney Type-I and Edney Type-II interaction, the heat transfer rates on the hemi-spherical body are symmetrical about the centerline of the body, with the peak heating at the centerline which drops towards the shoulder. For Edney Type-III, Edney Type-IV, Edney Type-V and Edney Type-VI interaction pattern, the distribution in not symmetrical and shifts in peak heat transfer rates being on the side of the hemispherical from which planar oblique shock wave is incident. Also, it is observed that for the interactions which appear within the sonic circle, Edney Type-III and Edney Type-IV, the heat transfer rates observe an unsteadiness, such that the gauges located close to the interaction region experiencing varying heat transfer rates during the useful test time of the shock tunnel. Few experiments were conducted at Mach 8.36 (total enthalpy of 1.29 MJ/kg; freestream velocity of 1555.25 m/s) and Mach 10.14 (total enthalpy of 2.67 MJ/kg; freestream velocity of 2258.51 m/s) for the con gurations representing Edney Type-III interaction pattern to further evaluate the unsteady nature observed at Mach 5.62 ows. The unsteadiness was evident in both the cases. It is realized that the short test times in the shock tunnels pose a constraint in the study of unsteady flow fields, and the use of tailored mode operation of shock tunnel can alleviate this constraint. Also, limited number of experiments in the present study, which are carried out in a Free Piston Shock Tunnel, helps to understand the need to conduct such study in high enthalpy test conditions.

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49

Ndebele, Bright Bekithemba. "The diffraction, reflection and propagation of cylindrical shock wave segments." Thesis, 2017. http://hdl.handle.net/10539/23544.

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A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in ful lment of the requirements for the degree of Doctor of Philosophy. Johannesburg, May 2017 Shock{waves (shocks) exist in various shapes; restricted to two dimensions some examples are planar, cylindrical, parabolic and elliptical. However, most shock{wave research has been focussed mostly on plane shocks. In this research, the scope is expanded to cylindrical shock{wave segments where a plane shock can be viewed as a cylindrical shock segment (referred to as a cylindrical shock) with a large radius of curvature; with this view, the expectations are that cylindrical and plane shocks behave similarly although with quantitative di erences. Whereas plane shocks have constant orientation, constant strength and can be imagined to extend unbounded, cylindrical shock segments demand that both ends be bound; this leads to spatial constraints, shock strength varying with respect to radius and shock orientation being non-constant. Three shock phenomena were investigated: di raction, re ection and propagation in converging diverging nozzles. Shock{tube experiments were run for shocks with a radius of 165 mm and strength between Mach numbers 1.2 and 1.7. Complementing these were Computational Fluid Dynamics (CFD) and Geometric Shock Dynamics (GSD) simulations where GSD relies on Whitham's equations. On shock di raction, cylindrical shocks were shown to behave qualitatively like plane shocks. Upon encountering a sharp corner, expansion waves propagate along the shock. However, after re ecting o the opposite wall they become compression waves and form a 'Mach re ection (MR)' like con guration on the shock front. A method for calculating the locus of the expansion waves based on Whitham's theory is presented, which on comparison with CFD simulations gives good correlation. Comparisons of shock pro les calculated using Whitham's theory and CFD is also made; it showed good correspondence before the formation of MR like con gurations after which the pro les di er. The re ection of cylindrical shocks was investigated from both an experimental and numerical perspective. Shock{tube experiments were run for shocks propagating on concave cylindrical walls with radii of 100 mm, 180 mm, 140 mm and 82 mm, the range was expanded by use of CFD. An expression for calculating the locus of the MR that forms on iii the shock front was derived which generalises onto plane shocks. Two limits were recognised, one where shock radius is much greater than wall radius and another where shock radius is much smaller. The former corresponds to a cylindrical shock on a plane wall while the latter a plane shock on a cylindrical wall as illustrated by the data gathered. Cylindrical shock propagation in converging-diverging nozzles was also investigated. In this case, the phenomena at play are di raction, re ection and focusing, a combination which results in a complex evolution of the shock front. Two types of channels were investigated, one formed from a 3rd order polynomial and another from circular arcs. In both cases, wall signal were generated on either side of the shock which split the shock{front into three sections. The decreasing channel cross{section area causes the shock strength to increase resulting in very weak MR formation on the shock front. Channels from circular walls exhibit a single peak in the centre line shock strength while that from polynomial pro le walls results in a double peak. This was then related to type of wall disturbance generated. MT 2017

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Bhaskar, K. "Studies On Shock Wave Attenuation In Liquids." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2041.

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The attenuation mechanism of shock waves of arbitrary strength propagating in air has been reasonably well understood. On the other hand, very little is known about the precise mechanism of shock wave attenuation and energy dissipation in liquids. The equation of state for shock propagation in water is empirical in nature and considerable differences exist with reference to the exact value of various constants even in the cast of Tait’ s equation of state, which is popularly used by researchers to describe the shock wave propagating through water. In recent times, considerable attention is being focused by researchers on shock wave attenuation and associated features in liquid medium mainly in the backdrop of development of many innovative industrial applications of shock waves. The present study focuses on generating reliable experimental data on shock wave attenuation in liquids of different viscosity. Experiments have been performed in a conventional vertical shock tube and a modified diaphragmless shock tube to understand how shock wave of requisite strength attenuates in liquids. A new vertical shock tube was designed, fabricated and successfully tested in the laboratory as a part of this study. In this new facility shock loading experiments with liquids or any complex fluid medium can be carried out. In the present study five liquids (Water, Castor Oil, Sodium Chloride (10%NaCl aqueous solution), Kerosene and Glycerin) have been subjected to shock wave loading. Exhaustive static pressure measurements in the liquid medium have been carried out to understand the attenuation characteristics of shock waves. The validity of Taits equation state has been experimentally verified for water. Based on the experimental results modified Taits equation of state has been obtained for castor oil, sodium chloride, kerosene and glycerin. Illustrative theoretical study is also carried out to complement the experiments.

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