Earthquake and submarine mass failure are the most frequent causes of tsunami waves. While the process of the tsunami generation by earthquakes is reasonably well understood, the generation of tsunami waves during submarine mass failure is not. Estimates of the energy released during a tsunamigenic earthquake and respective tsunami wave draw a clear picture of the efficiency of the tsunami-generating process. However for submarine landslides, this is not as straightforward because the generation process has never been recorded in nature making energy inferences very difficult. Hence the efficiency of submarine landslide as tsunami generators is yet to be conclusively determined. As the result of this uncertainty, different equations, derived from experimental data or theory, result in leading-wave amplitude that vary over 6 orders of magnitude for the same initial slide conditions. To arrive at more robust estimates of the leading-wave characteristics and associated runup, the spatiotemporal dynamics of the coupling between the slide body and water column needs to be investigated. The duration the water surface deformation is coupled with the slide motion is an essential question to shed light on the energy transfer. A parametric study is conducted with the state of-the-art hydrocode iSALE in order to shed light on this complex geophysical event. The mass, viscosity, and depth of submergence are the particular slide parameters varied and their relationship to runup and decoupling time is analyzed.

abstract: The study of deflagration to detonation transition (DDT) in explosives is of prime importance with regards to insensitive munitions (IM). Critical damage owing to thermal or shock stimuli could translate to significant loss of life and material. The present study models detonation and deflagration of a commonly used granular explosive: cyclotetramethylene-tetranitramine, HMX. A robust literature review is followed by computational modeling of gas gun and DDT tube test data using the Sandia National Lab three-dimensional multi-material Eulerian hydrocode CTH. This dissertation proposes new computational practices and models that aid in predicting shock stimulus IM response. CTH was first used to model experimental data sets of DDT tubes from both Naval Surface Weapons Center and Los Alamos National Laboratory which were initiated by pyrogenic material and a piston, respectively. Analytical verification was performed, where possible, for detonation via empirical based equations at the Chapman Jouguet state with errors below 2.1%, and deflagration via pressure dependent burn rate equations. CTH simulations include inert, history variable reactive burn and Arrhenius models. The results are in excellent agreement with published HMX detonation velocities. Novel additions include accurate simulation of the pyrogenic material BKNO3 and the inclusion of porosity in energetic materials. The treatment of compaction is especially important in modeling precursory hotspots, caused by hydrodynamic collapse of void regions or grain interactions, prior to DDT of granular explosives. The CTH compaction model of HMX was verified within 11% error via a five pronged validation approach using gas gun data and employed use of a newly generated set of P-α parameters for granular HMX in a Mie-Gruneisen Equation of State. Next, the additions of compaction were extended to a volumetric surface burning model of HMX and compare well to a set of empirical burn rates. Lastly, the compendium of detonation and deflagration models was applied to the aforementioned DDT tubes and demonstrate working functionalities of all models, albeit at the expense of significant computational resources. A robust hydrocode methodology is proposed to make use of the deflagration, compaction and detonation models as a means to predict IM response to shock stimulus of granular explosive materials. / Dissertation/Thesis / Doctoral Dissertation Aerospace Engineering 2015

El Antiproton Decelerator Target (AD-Target) es un dispositivo único responsable de la generación de Antiprotones en la Organización Europea para la Investigación Nuclear (CERN). En operación, intensos haces de protones con una energía de 26 GeV son impactados en su núcleo, un cilindro de 3 mm de diámetro constituido por un material de alta densidad como el iridio, creando partículas secundarias -entre ellas, antiprotones- como consecuencia de las reacciones nucleares inducidas en el interior de éste. La tesis profundiza en las características del target de producción de antiprotones, y en particular, en la respuesta mecánica de su núcleo, el cual está sometido a un incremento de temperatura de aproximademente 2000 grados centígrados en menos de 0.5 microsegundos cada vez que es impactado por el haz de protones primario. Para ello, una metodología combinando técnicas numéricas y experimentales ha sido llevada a cabo. Se han aplicado herramientas computacionales específicas, llamadas hydrocodes, para simular la respuesta dinámica originada en el núcleo del target y su matriz contenedora, hecha de grafito, indicando su potencial fragmentación como resultado de una onda radial de alta frecuencia de presión compresión-tracción generada después de cada impacto del haz de protones. Asimismo, se ha llevado a cabo un experimento llamado HiRadMat27. En éste, varios cilindros de materiales de alta densidad, candidatos para un futuro diseño del target, tales como Ir, W, W-La, Mo, TZM y Ta, han sido expuestos a condiciones dinámicas equivalentes a las alcanzadas en el AD-Target mediante impactos de haces de protones de 440 GeV en la instalación HiRadMat. Se ha usado instrumentación en línea para medir la onda radial pronosticada, confirmando la precisión de las simulaciones de hydrocodes. Todos los materiales irradiados excepto Ta sufrieron agrietamientos internos desde condiciones 5-7 veces menores a las presentes en el AD-Target, mientras que este último aparentemente sobrevivió. La información obtenida ha sido aplicada para proponer un nuevo diseño optimizado del target, el cual incluye un sistema de refrigeración de aire a presión, una nueva configuración en Ta de su núcleo, y una matriz contenedora hecha de grafito expandido (GE). Se han llevado a cabo cálculos de dinámica de fluidos computacional y elementos finitos para validar el sistema de refrigeración y la vida a fatiga del ensamblaje del target. Además, se ha construido un primer prototipo del núcleo del target y su matrix contenedora. Estas actividades marcan la senda para la fabricación de un nuevo lote de targets que garanticen la física de antiprotones en el CERN durante las siguientes décadas de operación. / The Antiproton Decelerator Target (AD-Target) is a unique device responsible for the production of antiprotons at the European Organization for Nuclear Research (CERN). During operation, intense 26 GeV energy proton beams are impacted into its core, made of a 3 mm diameter rod of a high density material such as iridium, creating secondary particles -including antiprotons- from the nuclear reactions induced in its interior. This thesis delves into the characteristics of antiproton production and in particular in the mechanical response of the target core material, which is exposed to a rise of temperature of approximate 2000 degrees Celsius in less than 0.5 microseconds each time is impacted by the primary proton beam. A coupled numerical-experimental approach has been applied for this purpose. Specific computational tools, called hydrocodes, have been used for simulating the extreme dynamic response taking place in the target core and its containing graphite matrix, indicating their potential damage and fragmentation as a result of a high frequency radial compressive-to-tensile pressure wave generated after each proton beam impact. A challenging first-of-its-kind experiment called HRMT27 was carried out. Several rods of high density materials, candidate for a future optimized target design, such as Ir, W, W-La, Mo, TZM and Ta were brought to equivalent dynamic conditions as reached in the AD-Target core by impacting them with 440 GeV proton beams using the HiRadMat facility. Online instrumentation was used to measure the predicted radial wave, confirming the accuracy of the hydrocode simulations. All of the irradiated target materials except Ta showed internal cracking from conditions 5-7 times below the present in the AD-Target while the latter apparently survived. Lessons learned are applied for proposing a new optimized target design, including a pressurized-air cooling system, Ta core configuration, and a containing matrix made of expanded graphite (EG). Computational Fluid Dynamic and Structural Finite Element analyses have been carried out to validate the new cooling system and fatigue life of the target assembly. A first prototype of the target core and its containing EG matrix has been built. These activities lead the way into manufacturing a new set of antiproton targets to guarantee antiproton physics at CERN during next decades of operation. / L'Antiproton Decelerator Target (AD-Target) és un dispositiu únic responsable de la generació d'Antiprotons a la Organització Europea per la Recerca Nuclear (CERN). En operació, intensos feixos de protons amb una energia de 26 GeV impacten contra el seu nucli, un cilindre de 3 mm de diámetre constituït per un material de densitat alta com l'iridi, creant partícules secundáries - entre elles, antiprotons - com a conseqüència de les reaccions nuclears induïdes a l'interior d'aquest. La tesis profunditza en les característiques del target de producció d'antiprotons i, en particular, a la resposta mecánica del seu nucli, el qual és sotmès a un increment de temperatura de aproximadement 2000 graus centígrads en menys de 0.5 microsegons cada vegada que és impactat pel feix de protons primari. Per aixó, s'ha portat a terme una metodologia que combina tècniques numèriques i experimentals. S'han utilitzat eines computacionals específiques, anomenades hydrocodes, per simular la resposta dinàmica originada al nucli del target i a la seva matriu contenidora, feta de grafit. La dita resposta, indica la seva potencial fragmentació com a resultat d'una ona radial d'alta freqüència de pressió compressió-tracció generada després de cada impact del feix de protons. Així mateix, s'ha portat a terme un experiment anomenat HiRadMat27. En aquest, varis cilindres de materials d'alta densitat, candidats per un futur diseny del target, tals com Ir, W, W-La, Mo, TZM i Ta, han estat exposats a condicions dinàmiques equivalents a les assolides a l'AD-Target mitjanant impactes de feixos de protons de 440 GeV a l'instalació HiRadMat. S'ha utilitzat instrumentació en línia per mesurar l'ona radial pronosticada, confirmant la precisió de les simulacions d'hydrocodes. Tots el materials irradiats excepte Ta van sofrir esquerdaments interns desde condicions de 5-7 vegades menors a les presents a l'AD-Target, mentres que aquest últim aparentment va sobreviure. L'informació obtinguda ha estat aplicada per proposar un nou diseny optimizat del target, el qual inclou un sistema de refrigeració de l'aire a pressió, una nova configuració en Ta del seu nucli, i una matriu contenidora feta de grafit expandit (GE). S'han portat a terme càlculs de dinàmica de fluids computacionals i elements finits per validar el sistema de refrigeració i la vida a fatiga de l'ensambladura del target. S'ha construit un primer prototip del nucli del target i la seva matriu contenidora. Totes aquestes activitats marquen la sendera per a la fabricació del nou lot de targets que garantitzin la física d'antiprotons al CERN durant les següents décades d'operació. / Torregrosa Martín, CL. (2018). Comprehensive Study and Optimized Redesign of the CERN's Antiproton Decelerator Target [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/100489 / TESIS

In this study, impact craters in water ice are modeled using the hydrodynamic code CTH. In order to capture impact craters in ice an equation of state and a material model are created and validated. The validation of the material model required simulating the Split Pressure Hopkinson Bar (SPHB) experimental apparatus. The SPHB simulation was first compared to experiments completed on Al 6061-T6, then the ice material model was validated. After validation, the cratering simulations modeled known experiments found in the literature. The cratering simulations captured the bulk physical aspects of the experimental craters, and the differences are described. Analysis of the crater simulations showed the damaged volume produced by the projectile was proportional to the projectile’s momentum. Also, the identification of four different stages in the crater development of ice (contact and compression, initial damage progression, crater shaping, and ejected damaged material) are described.

The objective of this research was to evaluate the capabilities of ALEGRA, a Sandia National Labs hydrocode, and Forge3, a Transvalor S.A. product, to accurately model the Friction Stir Welding Process. ALEGRA and Forge3 are discussed in light of the inherent challenges of modeling Friction Stir Welding, and a rotational boundary condition is added to ALEGRA. Results are presented from Friction Stir Welding modeling outputs from both ALEGRA and Forge3. ALEGRA is shown to be incapable of modeling the Friction Stir Welding process, in large part due to its focus on shock propagation, which causes extremely small time steps. Forge3 is shown capable of modeling of the FSW plunge process in a transient manner, but overestimates the temperature profiles 90% to 100% in comparison to experimentally measured values. It appears that the adiabatic boundary condition is the source of much of the error. It is recommended that future work focus on improving estimates of the boundary conditions utilized in the Forge3 model.

Energetic structural materials (ESMs) constitute a new class of materials that provide dual functions of strength and energetic characteristics. ESMs are typically composed of micron-scale or nano-scale intermetallic mixtures or mixtures of metals and metal oxides, polymer binders, and structural reinforcements. Voids are included to produce a composite with favorable chemical reaction characteristics. In this thesis, a continuum approach is used to simulate gas-gun or explosive loading experiments where a strong shock is induced in the ESM by an impacting plate. Algorithms are developed to obtain equations of state of mixtures. It is usually assumed that the shock loading increases the energy of the ESM and causes the ESM to reach the transition state. It is also assumed that the activation energy needed to reach the transition state is a function of the temperature of the mixture. In this thesis, it is proposed that the activation energy is a function of temperature and the stress state of the mixture. The incorporation of such an activation energy is selected in this thesis. Then, a multi-scale chemical reaction model for a heterogeneous mixture is introduced. This model incorporates reaction initiation, propagation, and extent of completed reaction in spatially heterogeneous distributions of reactants. A new model is proposed for the pore collapse of mixtures. This model is formulated by modifying the Carol, Holt, and Nesterenko spherically symmetric model to include mixtures and compressibility effects. Uncertainties in the model result from assumptions in formulating the models for continuum relationships and chemical reactions in mixtures that are distributed heterogeneously in space and in numerical integration of the resulting equations. It is important to quantify these uncertainties. In this thesis, such an uncertainty quantification is investigated by systematically identifying the physical processes that occur during shock compression of ESMs which are then used to construct a hierarchical framework for uncertainty quantification.

abstract: Mathematical models are important tools for addressing problems that exceed experimental capabilities. In this work, I present ordinary and partial differential equation (ODE, PDE) models for two problems: Vicodin abuse and impact cratering. The prescription opioid Vicodin is the nation's most widely prescribed pain reliever. The majority of Vicodin abusers are first introduced via prescription, distinguishing it from other drugs in which the most common path to abuse begins with experimentation. I develop and analyze two mathematical models of Vicodin use and abuse, considering only those patients with an initial Vicodin prescription. Through adjoint sensitivity analysis, I show that focusing efforts on prevention rather than treatment has greater success at reducing the total population of abusers. I prove that solutions to each model exist, are unique, and are non-negative. I also derive conditions for which these solutions are asymptotically stable. Verification and Validation (V&V) are necessary processes to ensure accuracy of computational methods. Simulations are essential for addressing impact cratering problems, because these problems often exceed experimental capabilities. I show that the Free Lagrange (FLAG) hydrocode, developed and maintained by Los Alamos National Laboratory, can be used for impact cratering simulations by verifying FLAG against two analytical models of aluminum-on-aluminum impacts at different impact velocities and validating FLAG against a glass-into-water laboratory impact experiment. My verification results show good agreement with the theoretical maximum pressures, and my mesh resolution study shows that FLAG converges at resolutions low enough to reduce the required computation time from about 28 hours to about 25 minutes. Asteroid 16 Psyche is the largest M-type (metallic) asteroid in the Main Asteroid Belt. Radar albedo data indicate Psyche's surface is rich in metallic content, but estimates for Psyche's composition vary widely. Psyche has two large impact structures in its Southern hemisphere, with estimated diameters from 50 km to 70 km and estimated depths up to 6.4 km. I use the FLAG hydrocode to model the formation of the largest of these impact structures. My results indicate an oblique angle of impact rather than a vertical impact. These results also support previous claims that Psyche is metallic and porous. / Dissertation/Thesis / Psyche asteroid impact simulation initialization / Psyche asteroid impact simulation video / Doctoral Dissertation Applied Mathematics 2019

A hydrocode and an explicit finite element code were used to evaluate functionally graded material impacts, meteor impacts, and split Hopkinson pressure bar specimens. Modeling impacts of functionally graded projectiles revealed that density was the primary material characteristic controlling the shock wave profile. A parametric study of material order for functionally graded armor showed that arranging the weaker material in front created the greater stopping power. By modeling an array of meteor impact scenarios, deformation and stress were shown to occur at great depths and possibly cause tectonic movement, like subduction. Three proposed Hopkinson specimens, which were designed to produce either shear or tensile reactions under compressive loading, were evaluated. For two of these specimens, improved stress and strain equations were presented.

Underwater explosions are often modeled with Arbitrary Lagrangian-Eulerian (ALE) Finite Element Methods. The objective of this thesis is to validate the simulation method, with respect to the propagating shock wave. A two-dimensional axisymmetric model of a spherical TNT charge submerged in water is simulated using LS-DYNA. The explosive is modeled with the Burn Fraction technique and the Jones-Wilkins-Lee equation of state. Water is modeled as a non-viscous fluid, with the Grüneisen equation of state. The convergence for different mesh resolutions, the effect of different advection methods, and varied constants in the artificial viscosity are examined. Generally, the simulations agree well with empirical results, but the maximum pressure diminishes more rapidly with distance compared to experiments. The excessive dampening is most notable in the early stages of the propagation. Also, unexpected oscillations are observed near the discontinuity. The choice of advection scheme and constants in the artificial viscosity do not resolve the issues suggesting that other numerical techniques for treating the discontinuity should be considered. / Undervattensexplosioner simuleras ofta med ALE-baserade finita elementmetoder. Detta examensarbete avser att validera simuleringsmetoden med hänsyn till stötvågens utbredning i vattnet. En tvådimensionell axisymmetrisk modell av en sfärisk TNT-laddning nedsänkt i vatten simuleras i LS-DYNA. Laddningen modelleras med hjälp av brinnfraktioner och Jones-Wilkins-Lee tillståndsekvation. Vattnet modelleras som en inviskös fluid tillsammans med Grüneisens tillståndsekvation. Nätkonvergens, val av advektionsmetod och ändring av konstanter i den artificiella viskositeten studeras. Övergripande resultat stämmer väl överens med empirisk data, men stötvågens topptryck avtar fortare än väntat. Denna dämpning är tydligast i utredningens tidiga skeden. Dessutom observeras oväntade oscillationer kring stötvågens diskontinuerliga tryckprofil. Val av advektionsmetod och konstanter tillhörande artificiella viskositeten verkar ha liten betydelse för resultaten. En alternativ numerisk metod för behandling av stötvågens diskontinuitet bör implementeras.

A research study has been conducted to simulate liquefaction in saturated sandy soil induced by nearby controlled blasts. The purpose of the study is to help quantify soil characteristics under multiple and consecutive high-magnitude shock environments similar to those produced by large earthquakes. The simulation procedure involved the modeling of a three-dimensional half-space soil region with pre-defined, embedded, and strategically located explosive charges to be detonated at specific time intervals. LS-DYNA, a commercially available finite element hydrocode, was the solver used to simulate the event. A new geo-material model developed under the direction of the U.S. Federal Highway Administration was applied to evaluate the liquefaction potential of saturated sandy soil subjected to sequential blast environments. Additional procedural enhancements were integrated into the analysis process to represent volumetric effects of the saturated soil's transition from solid to liquid during the liquefaction process. Explosive charge detonation and pressure development characteristics were modeled using proven and accepted modeling techniques. As explosive charges were detonated in a pre-defined order, development of pore water pressure, volumetric (compressive) strains, shear strains, and particle accelerations were carefully computed and monitored using custom developed MathCad and C/C++ routines. Results of the study were compared against blast-test data gathered at the Fraser River Delta region of Vancouver, British Columbia in May of 2005 to validate and verify the modeling procedure's ability to simulate and predict blast-induced liquefaction events. Reasonable correlations between predicted and measured data were observed from the study.