A Pulse Detonation Engine (PDE) is a propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the transition of a subsonic deflagration, created using low initiation energies, to a supersonic detonation. This thesis presents the effects of obstacle spacing, blockage ratio, DDT section length, and airflow on DDT behavior in hydrogen-air and ethylene-air mixtures for a repeating PDE. These experiments were performed on a 2 diameter, 40 long, continuous-flow PDE located at the General Electric Global Research Center in Niskayuna, New York. A fundamental study of experiments performed on a modular orifice plate DDT geometry revealed that all three factors tested (obstacle blockage ratio, length of DDT section, and spacing between obstacles) have a statistically significant effect on flame acceleration. All of the interactions between the factors, except for the interaction of the blockage ratio with the spacing between obstacles, were also significant. To better capture the non-linearity of the DDT process, further studies were performed using a clear detonation chamber and a high-speed digital camera to track the flame chemiluminescence as it progressed through the PDE. Results show that the presence of excess obstacles, past what is minimally required to transition the flame to detonation, hinders the length and time to transition to detonation. Other key findings show that increasing the mass flow-rate of air through the PDE significantly reduces the run-up time of DDT, while having minimal effect on run-up distance. These experimental results provided validation runs for computational studies. In some cases as little as 20% difference was seen. The minimum DDT length for 0.15 lb/s hydrogen-air studies was 8 L/D from the spark location, while for ethylene it was 16 L/D. It was also observed that increasing the airflow rate through the tube from 0.1 to 0.3 lbs/sec decreased the time required for DDT by 26%, from 3.9 ms to 2.9 ms.

Der bisher noch wenig untersuchte Wellenaufgang im Übergangsbereich zwischen Brandung und Reflexion wurde experimentell untersucht. Darauf aufbauend wird ein geschlossener Berechnungsansatz für die Auflaufhöhe unregelmäßiger Wellen vorgeschlagen, der für brechende und nichtbrechende Wellen anwendbar ist.

This thesis explores the geomorphic implications of large woody debris (LWD) residing in the backshore of beach-dune systems along the northeastern coasts of Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada. Detailed topographic surveys were employed to quantify seasonal mass balance of the beach-dune systems along two distinctly different coastlines. Erosion and accretion potential models were applied to characterize sediment transport conditions. Holman’s (1986) R2% wave runup model was superimposed on total water levels, to model wave runup exceedence of the beach-dune junction elevation (6.5 m aCD). Modelled ‘erosion potential’ hours were demonstrated to correspond with observed erosion including removal of the LWD zone, resulting in decreased mass balance. Similarly, Fryberger and Dean’s (1979) Drift Potential model was used to model accretion potential hours. Modelled accretion potential hours were also able to effectively describe conditions when actual accretion occurred. The presence of LWD in the backshore offered two functions to the above processes: it acted effectively as an ‘accretion anchor’, promoting increased mass balance and rebuilding of the incipient foredune; and, it offered a mass of sediment fronting the foredune to protect the beach-dune system from storm wave attack and subsequent erosion.

Magíster en Ciencias, Mención Geofísica / En esta tesis se propone una solución analítica de la ecuación de ondas de agua poco profunda inhomogénea aplicado a problema de deslizamientos de tierra, donde el problema tiene condiciones iniciales nulas. Se desarrollaron tres modelos matemáticos como representantes del movimiento del fondo marino; el primero consiste en una función de variable separable que depende del espacio físico (x) y del tiempo (t), donde la función del tipo gaussiana depende de x y la función tipo caja depende de t. El segundo modelo consiste en una función del tipo caja, esta función mantiene la forma en el tiempo, y se mueve a una velocidad constante sobre un plano inclinado. Este segundo modelo fue la base teórica para desarrollar el tercer y definitivo modelo matemático propuesto por este trabajo, y consiste en una función forzante del tipo parabólica invertida, la cual se mueve a una velocidad constante sobre un plano inclinado. Este tercer modelo mantiene su forma en el tiempo, independiente si se mueve indefinidamente. La solución analítica proveniente de este tercer modelo corresponde a la altura de runup de un tsunami provocado por un deslizamiento de tierra. Esta solución analítica fue comparada con soluciones obtenidas por el método de diferencias finitas y con otros estudios. Todos estos métodos fueron aplicados a los tsunamis generados por deslizamientos de tierra subaéreos en Aguas Calientes y frente a Isla Mentirosa (ambos ocurridos en el Fiordo de Aysén en el año 2007), y también el tsunami provocado por un deslizamiento de tierra submarino ocurrido en Papua Nueva Guinea en el año 1998. Para los eventos del Fiordo de Aysén, se obtuvieron resultados dispares, ya que para el deslizamiento frente a Isla Mentirosa, se sobreestimaron las alturas máximas de runup; y para el deslizamiento de tierra subaéreo de Aguas Calientes se subestimó la altura de runup medida insitu. Sin embargo, debido a la falta de datos y mediciones de campo en el fiordo de Aysén, ambos resultados sirven como valores de referencia para investigaciones futuras. Para el evento de Papua Nueva Guinea, se modelaron dos casos, el primero correspondiente al modelo de playa inclinada de pendiente constante, cuyo ángulo de la pendiente fue tomado de la literatura, el cual es igual a 12°. El segundo modelo también corresponde a un modelo de playa inclinada, donde los datos batimétricos fueron obtenidos de General Bathymetric Chart of the Oceans. La forma de calcular la pendiente fue mediante el método de mínimos cuadrados, cuyo resultado fue de 4,81°. Para ambos modelos se predijeron las alturas de runup medidos insitu, no sin ligeras modificaciones de los parámetros, tales como: el espesor, la velocidad y el largo del deslizamiento de tierra. En este trabajo de tesis se propone que la teoría de los tsunamis generados por impactos de meteoritos sea la base de estudio para investigaciones futuras sobre el fenómeno de los deslizamientos de tierra subaéreos.

Der bisher noch wenig untersuchte Wellenaufgang im Übergangsbereich zwischen Brandung und Reflexion wurde experimentell untersucht. Darauf aufbauend wird ein geschlossener Berechnungsansatz für die Auflaufhöhe unregelmäßiger Wellen vorgeschlagen, der für brechende und nichtbrechende Wellen anwendbar ist.

Coastal sand dunes play an important role in the littoral processes of California’s coastline. Functioning as both source and sink for sand, these dunes often protect coastal infrastructure and provide a buffer between anthropogenic development and coastal forces. At Toro Creek Beach, north of Morro Bay California, recent extreme winter storms have raised concerns about the erosion of the sand dunes that front California State Highway 1. This thesis attempts to characterize the historical growth and recession patterns of the Toro Creek dunes since 1977, the dune movement over the 2023-2024 winter seasons, the wave forcings behind recent high erosion events, and potential impacts of sea level rise. Four topographic surveys of the beach were conducted through the winter of 2024 and showed evidence of -11.5 ft and -12.8 ft of erosion north and south of the Toro Creek bridge. Historical aerial and satellite imagery was used to delineate the extent of the dunes at Toro Creek and estimate dune movement during this period. From 1977-2023, the dunes moved seaward 37.4 ft and 126.6 ft north and south of the bridge. Throughout this period, temporal erosion and accretion is seen on both sides of the bridge. The winters of 2021-2024 display dune erosion on at least one side of the Highway 1 bridge that approaches or exceeds yearly retreat rates developed by the USGS for shoreline (-4.9 ft/yr) and coastal cliffs (-1.6 ft/yr) in the Morro Bay area. Of these winters, 2023 witnessed the most erosion: -33.3 ft north of the bridge and ‑1.1 ft south of the bridge. This study utilized wave data from the Diablo Canyon Waverider buoy to develop a significant wave height climate specific to the orientation of Toro Creek Beach. Using tide data from the National Oceanic and Atmospheric Administration (NOAA) tide gauge in Port San Luis, I estimated total water level—the summation of significant wave height and tide—for Toro Creek. Subsequently, I evaluated wave runup using an empirical equation developed by Stockdon et al. (2006). I analyzed the total water level and runup height—the summation of runup and tidal stage—along with other coastal processes like wave direction and refraction during the peak events of the 2021-2024 winters. Among these years, 2023 experienced total water levels as high as 16.3 ft, and runup values as high as 14.3 ft—some of the highest since the start of analyzed wave data. Additionally, I calculated the impact sea level rise (SLR) would have on runup using our wave data, under an extreme sea level rise scenario of 6.4 ft. The number of 24-hour days per year during which runup height exceeds the extreme runup height reached during the December 28, 2023 storm increases from 0.01 to 95.06 with 6.4 ft SLR. The exceedance of the 17 ft FEMA Coastal Flood Zone VE elevation for Toro Creek increases from 0 to 6.60 24-hour days per year with 6.4 ft SLR. Overall, this study shows that dune erosion accompanies high wave runup heights, and that future SLR will increase the likelihood of dune erosion at Toro Creek beach.

À partir d'une approche basée sur l'étude d'évènements de submersion passés et d'épisodes observés durant ce travail, l'objectif de cette thèse était de mieux comprendre les processus atmosphériques, météo-marins et hydro-sédimentaires qui interviennent lors des submersions marines sur les côtes bretonnes. Dans un premier temps, tous les épisodes de submersions marines qui ont eu lieu depuis 1960 en Bretagne sont recensés puis analysés à une échelle régionale afin de cibler les situations atmosphériques considérées comme " à risque ". L'analyse des conditions synoptiques durant ces épisodes passés montre que la position du centre dépressionnaire et le gradient de pression au moment des pleines mers, jouent un rôle essentiel dans la localisation des secteurs submergés. Le gradient de pression s'avère être l'élément fondamental car il détermine l'ensemble des paramètres qui rentrent en compte dans l'élévation exceptionnelle du niveau d'eau à la côte. L'analyse de l'évolution de ces situations atmosphériques depuis les cinquante dernières années indique une augmentation des situations à fort gradient de pression de sud-ouest et une baisse des épisodes de nord-ouest et de nord-est. Dans un deuxième temps, l'étude des processus météo-marins à l'échelle locale indique que depuis 1960, 95 % des submersions ont été générées par la combinaison d'une marée à fort coefficient, d'une surcote (générée par une faible pression atmosphérique et l'action de vents d'afflux) et d'une forte agitation marine. En Bretagne, le passage de fronts froids actifs n'intervient que dans 30 % des cas de submersion mais peut jouer un rôle sur certains sites. L'étude du phénomène de runup à partir de mesures in situ sur deux plages du Finistère apporte un certain nombre de réponses aux questions relatives à ce phénomène jusqu'alors peu étudié. En milieu macrotidal et mégatidal, l'emploi de la pente de la zone intertidale avec les formules issues de la littérature sous-estime vraisemblablement les valeurs de runup. L'utilisation de la pente de la portion mobile prévaut. Dans un troisième temps, la question du risque de submersion marine a été abordé à travers une démarche de recherche appliquée. Une méthode de prévision multi-scalaire des situations à risque en Bretagne et une méthode de cartographie du risque de submersion sont élaborées.

Analytical solutions for the linear and nonlinear shallow-water wave equations are developed for evolution and runup of tsunamis &ndash / long waves&ndash / over one- and two-dimensional bathymetries. In one-dimensional case, the nonlinear equations are solved for a plane beach using the hodograph transformation with eigenfunction expansion or integral transform methods under different initial conditions, i.e., earthquake-generated waves, wind set-down relaxation, and landslide-generated waves. In two-dimensional case, the linear shallow-water wave equation is solved for a flat ocean bottom for initial waves having finite-crest length. Analytical verification of source focusing is presented. The role of focusing in unexpectedly high tsunami runup observations for the 17 July 1998 Papua New Guinea and 17 July 2006 Java Island, Indonesia tsunamis are investigated. Analytical models developed here can serve as benchmark solutions for numerical studies.

Our paleotsunami surveys of the southern Java coast led to the discovery of five imbricate coastal boulder fields near Pacitan, Indonesia that may date to the mid-to-late 19th century or prior and two similar fields at Pantai Papuma and Pantai Pasir Putih that were tsunami-emplaced during the 1994 7.9 Mw event in East Java. Estimated ages for the fields near Pacitan are based on historical records and radiocarbon analyses of coral boulders. The largest imbricated boulders in fields near Pacitan and in East Java are similar in size (approximately 3 m^3) and are primarily composed of platy beachrock dislodged from the intertidal platform during one or several unusually powerful wave impactions. Hydrodynamic wave height reconstructions of the accumulations near Pacitan indicate the boulders were likely tsunami rather than storm-wave emplaced, as the size of the storm waves needed to do so is not viable. We evaluate the boulders as an inverse problem, using their reconstructed wave heights and ComMIT tsunami modeling to suggest a minimum 8.4 Mw earthquake necessary to dislodge and emplace the largest boulders near Pacitan assuming they were all deposited during the same tsunami event and that the rupture source was located along the Java Trench south of Pacitan. A combined analysis of historical records of Java earthquakes and plate motion measurements indicates a seismic gap with >25 m of slip deficit along the Java Trench. A 1000-1500 km rupture along the subduction interface of this segment is capable of producing a 9.0-9.3 Mw megathrust earthquake and a giant tsunami. However, evidence for past megathrust earthquake events along the this trench remains elusive. We use epicenter independent tsunami modelling to estimate wave heights and inundation along East Java in the event that the trench were to fully rupture. By translocating ComMIT slip parameters of Japan's 2011 9.1 Mw event along the trench offshore East Java, we demonstrate possible wave heights in excess of 20 m at various locations along its southern coasts. Approximately 300,000-500,000 people in low-lying coastal communities on the southern coasts of East Java could be directly affected. We recommend at-risk communities practice the "20/20/20 principle" of tsunami hazard awareness and evacuation.

Hurricane hazards result from the combined processes of wind, waves, storm surge, and overwash (Lennon et al., 1996). Predicting the severity of these hazards requires immense effort to quantify the processes and then predict how different coastal regions respond to them. A somewhat simpler, but no less daunting task is to begin to predict the hazards due to potential erosion of barrier islands. A four-part scale has been developed by Sallenger (2000) to provide a framework for understanding how barrier islands might respond during extreme storm events. These four regimes describe how beach and dune elevations interact with surge and wave runup. This study will produce estimates of potential hazards through combining lidar surveys of dune elevation with modeled elevations of storm water levels. Direct measurements of maximum wave heights during hurricanes are rare. We evaluated three simple equations proposed by Kjerfve (1986), Young (1988), and Hsu (1998) to forecast the maximum wave height (Hmax) generated by three 1999 hurricanes. Model results were compared to wave data recorded by the National Oceanic and Atmospheric Administration (NOAA) wave rider buoys. The radius of maximum winds, wind speed, forward velocity, distance from buoy to the storm's eye-wall (r), and buoy's position relative to the quadrant of the storm (Q) were found to have significant and direct roles in evaluating recorded hurricane induced wave heights (H) and thus, were individually examined for each comparison. The implications of the r and Q on H were assessed when determining the overall effectiveness of the modelers' equations. Linear regression analyses tested the accuracy of each modeled prediction of the Hmax, comparing it to the observed wave heights. Three statistical criteria were used to quantify model performance. Hsu's model was the most reliable and useful forecasting technique. Despite the predictive skill of Hsu's model, direct observations of the maximum wave conditions, when available and appropriate, are preferred as inputs for SWAN, a 3rd generation shoaling wave model. Outputs from SWAN are used to calculate the empirical relationships for wave runup. For our test case, pre and post-storm topographies were surveyed as part of a joint USGS-NASA program using lidar technology. These data sets were used to calculate changes in the elevation and location of the dune crest (Dhigh) and dune base (Dlow) for the North Carolina Outer Banks. We hindcast potential coastal hazards (erosional hot spots) using the pre-storm morphology and modeled wave runup and compare those estimates to the measured results from the post-storm survey. Links among the existing topography and spatial variations in wave runup were found to be 95% correlated for the north-south and east-west facing barrier islands. Application of Sallenger's (2000) four-part Storm Impact Scale to the pre-storm Dhigh elevation survey and wave runup extremes (Rhigh and Rlow) were found to accurately predict zones of overwash and showed potential to forecast the inundation regime.