Dissertations / Theses on the topic 'Wave slope'

Wave reflection of sea-swell (0.050.20 Hz) energy on a two-slope (1/7.6 nearshore and 1/19 offshore) steep beach with no subaqueous sandbar is studied. The dataset were collected using a cross-shore array of 4 Acoustic Doppler Current Profilers measuring velocity and pressure at 1 Hz continuously for 40 days. Measurement of pressure and velocity at the same location allows data to be decomposed into onshore and offshore components to determine reflection. The long data set captured a wide range of wave conditions at various tidal stages. Observations show low amplitude long period waves produced energy reflection coefficients up to 80%, with most in the 3050% range. There was a measured increase in the number of nodes and anti-nodes at higher frequencies and observations farther offshore consistent with theory. Field data were compared to an analytical two-slope model that predicts the cross-shore nodal structure of standing waves. The predicted locations of nodes and anti-nodes are in good agreement with observations.

This thesis presents results of a study of the acoustic emission (AE) monitoring technique for detecting slope deformations. Laboratory studies carried out at Nottingham Trent University to develop and assess an acoustic emission monitoring system, including data processing and interpretation criteria, are described. Due to the low energy of soil generated AE and their high attenuation as they propagate through soil, a key element of the system is the wave guide used to transmit signals from depth within the deforming soil body to the sensor at ground level. This investigation is centred on assessing the performance of 'active' wave guides. A steel tube is located in a pre-drilled borehole with granular surround. Deformation of the host soil results in deformation of the wave guide/backfill system and generation of AE. Interpretation requires information on the location of generated AE along the length of the wave guide and on the relationship between AE and ground deformation rates. Each component of the wave guide system has been investigated to assess its influence on the generated and transmitted signal (i.e. wave guide diameter, connection type, sensor attachment details and backfill soil grading). The main findings from the study are: a) soil generated AE signals can be generated and transmitted by an active wave guide; b) high attenuation and signal dispersion can result from poor connections between wave guide lengths and this reduces the sensitivity of the system; c) AE levels emitted due to bending of the steel wave guide are negligible and need not be considered; d) the source of AE along the wave guide can be located using only one transducer by identifying different velocity signal wave modes (Lamb waves) that travel through thin walled pipes; e) sand backfill soil is responsive to faster deformation rates than gravel and AE amplitude increases with displacement; f) gravel backfill generates detectable AE even under extremely slow rate of deformation (10-4mm1min) and AE increases with displacement but with constant amplitude. This research demonstrates the ability of active wave guides to generate AE in response to very slow ground deformation rates, and hence its potential to provide an early warning of slope instability.

Simulation models based on the elliptic mild or steep slope wave equation are frequently used to estimate wave properties needed for the engineering calculations of harbors. To increase the practical applicability of such models, a method is developed to include the effects of rubble mound structures that may be present along the sides of entrance channels into harbors. The results of this method are found to match those of other mathematical models (i.e. parabolic approximation & three-dimensional solution) under appropriate conditions, but they also deviate from results of parabolic approximations in some cases because dissipation can create angular scattering. Comparison with hydraulic model data also shows that this approach is useful for designing pocket wave absorbers that are used to reduce wave heights in entrance channels.

Internal waves exist everywhere in stratified fluids - fluids whose density changes with depth. The two largest bodies of stratified fluid are the atmosphere and ocean. Internal waves are generated from a variety of mechanisms. One common mechanism is wind forcing over repeated sinusoidal topography, like a series of hills. When modeling these waves, linear theory has been employed due to its ease and low computational cost. However, recent research has shown that non-linear effects, such as boundary layer separation, may have a dramatic impact on wave generation. This research has consisted of experimentation on sloped, sinusoidal hills. As of yet, no experimental research has been done to characterize internal wave generation when repeated sinusoidal hills lie on a sloped surface such as a continental slope or a foothill. In order to perform this experiment, a laboratory was built which employed the synthetic schlieren method of wave visualization. Measurements were taken to find wind speed, boundary layer thickness, and density perturbation. From these data, an analysis was performed on wave propagation angle, wave amplitude, and pressure drag. The result of the analysis shows that when wind blows across a series of sloped sinusoidal hills, fluid becomes trapped in the troughs of the hills resulting in a lower apparent forcing amplitude. The generated waves contain less energy than linear predictions. Additionally, the sloped hills produce waves which propagate at an angle away from the viewer. A necessary correction, which shifts from the reference frame of the observer to the reference plane of the waves is described. When this correction is applied, it is shown that linear theory may only be applied for low Froude numbers. At high Froude numbers, the effect of the boundary layer is great enough that the wave characteristics deviate significantly from linear theory predictions. The analyzed data agrees well with previous studies which show a similar deviation from linear theory.

The design of rubble mound breakwaters usually focuses on the main armor layer. A review of the existing literature reveals that different equations are used to design rock armors in non-breaking wave conditions. However, most rubble mound breakwaters are constructed in the depth-induced breaking zone where they are attacked by waves breaking in the foreshore; in these conditions, existing design equations are not valid. Therefore, in this PhD thesis, the hydraulic stability of double-layer rock armors is analyzed through a series of small-scale tests conducted with a bottom slope m=1/50. Based on test results, a new potential relationship is given to design rock armors in depth-limited breaking wave conditions with armor slope cot¿=1.5, stability numbers within the range 0.98¿Hm0/(¿Dn50)¿2.5, and relative water depth at the toe 3.75¿hs/(¿Dn50)¿7.50. When concrete units are used for the armor layer, mound breakwaters are usually protected by a toe berm. This toe berm is placed on the seafloor or underlayer, providing support for the concrete armor units which are placed later on the structure slope. Toe berm design is commonly related to the armor design; in non-breaking wave conditions, the mass of toe berm rocks is one order of magnitude lower than the units of the layer. In breaking wave conditions, however, the highest waves start breaking on the bottom and impact directly on the toe berm. This is the common case of rocky sea bottoms with m=1/10 or higher slopes and thus, a correct design of the toe berm is crucial to guarantee the armor stability. The present PhD thesis examines the hydraulic stability of rock toe berms placed on a m=1/10 bottom slope and in very shallow waters (0.53Dn50): (1) the nominal toe berm or the most shoreward toe berm area which effectively supports the armor layer, and (2) the sacrificial toe berm or the most seaward toe berm area which serves to protect the nominal toe berm. Considering the nominal toe berm damage, a new method is developed to reduce the rock toe berm size (Dn50) by increasing the toe berm width (Bt) if the required rock size is not available at the quarries. Finally, cube armor damage is examined, and the influence of the placement technique on armor stability is also characterized from physical tests conducted with cubes randomly- and uniformly- placed on the armor in two layers.
El manto principal de los diques en talud suele estar formado por escollera natural o elementos prefabricados de hormigón; su función es resistir la acción del oleaje. Una revisión del estado del arte pone de manifiesto que son numerosas las fórmulas existentes para el diseño de mantos derivadas de ensayos físicos a escala reducida con oleaje sin rotura por fondo. Sin embargo, la mayoría de diques en talud se construyen en la zona de rompientes con oleaje limitado por fondo, donde las ecuaciones de diseño habituales no son del todo válidas. En esta tesis doctoral se analiza la estabilidad hidráulica de mantos bicapa de escollera, a partir de ensayos a escala reducida con pendiente de fondo m=1/50. En base a los resultados obtenidos de los ensayos físicos, se propone una nueva relación potencial para el diseño de mantos de escollera en condiciones de oleaje limitado por fondo, válida para taludes con cot¿=1.5, números de estabilidad 0.98¿Hm0/(¿Dn50)¿2.5, y profundidades relativas a pie de dique de 3.75¿hs/(¿Dn50)¿7.50. Cuando el manto principal está formado por elementos de hormigón, es habitual construir una berma de pie que proporciona apoyo a los elementos del manto y, en su caso, colabora en la protección de la zona inferior del dique contra la socavación. Dicha berma suele construirse con escollera natural y su peso está condicionado al de los elementos del manto en el caso de no haber rotura por fondo. El peso de los elementos de la berma de pie suele ser un orden de magnitud inferior al peso de las unidades del manto; sin embargo, si la pendiente de fondo es fuerte (p.e. m=1/10) y las aguas someras esta regla no se cumple ya que algunas olas rompen sobre el fondo impactando directamente sobre la berma de pie. En estos casos, el peso de la escollera de la berma puede sobrepasar el de las unidades del manto y su correcto diseño es crucial para garantizar la estabilidad del dique. Además de estudiar la estabilidad del manto principal de diques de escollera, la presente tesis doctoral analiza también la estabilidad hidráulica de bermas de pie de escollera ubicadas en fondos con pendiente m=1/10 y aguas someras (0.53Dn50): (1) berma nominal o zona de la berma de pie sobre la que realmente apoya el manto principal, y (2) berma de sacrificio o zona de la berma de pie que protege a la berma nominal. A partir del daño de la berma de pie nominal, se propone un nuevo método para reducir el tamaño de piedra (Dn50) incrementando el ancho de la berma (Bt) cuando no se disponga del tamaño requerido en cantera. Finalmente, se examina el daño del manto de cubos y se analiza la influencia del método de colocación sobre el mismo, a partir de ensayos realizados con mantos bicapa de cubos con colocación aleatoria y uniforme.
El mantell principal dels dics en talús sol estar format per roca o elements prefabricats de formigó, la seva funció és resistir l'acció de l'onatge. Una revisió de l'estat de l'art manifesta que són nombroses les equacions de disseny existents per a condicions d'onatge no trencat. No obstant això, la majoria de dics en talús es construeixen a la zona de rompents amb onatge limitat per fons, on les equacions de disseny existents no són del tot vàlides. En aquesta tesi doctoral s'analitza l'estabilitat hidràulica de mantells bicapa de roca, a partir d'assajos a escala reduïda realitzats amb pendent de fons m = 1/50. En base als resultats obtinguts dels assajos, es proposa una relació potencial per al disseny de mantells de roca en condicions d'onatge limitat per fons vàlida per a talussos amb cot¿ = 1.5, nombres d'estabilitat 0.98¿Hm0/(¿Dn50) ¿2.5, i profunditats relatives a peu de dic de 3.75¿hs/(¿Dn50)¿7.50. Quan mantell principal està format per elements de formigó , és habitual construir una berma de peu que proporciona suport als elements del mantell i, si escau, col¿labora en la protecció de la zona inferior del dic contra la soscavació. Aquesta berma sol construir amb roca i el seu pes està condicionat al dels elements del mantell en el cas de no haver trencament per fons. El pes dels elements de la berma de peu sol ser un ordre de magnitud inferior al pes de les unitats del mantell; però, si el pendent de fons és fort ( p.e. m = 1 /10) i les aigües someres aquesta regla no es compleix ja que algunes onades trenquen sobre el fons impactant directament sobre la berma de peu. En aquests casos, el pes de la roca de la berma pot sobrepassar el de les unitats del mantell, i el seu correcte disseny és crucial per garantir l'estabilitat del dic. A més d'estudiar l'estabilitat del mantell principal de dics de roca, la present tesi doctoral analitza també l'estabilitat hidràulica de bermes de roca ubicades en fons amb pendents m = 1/10 i aigües someres (0.5 3 Dn50): (1) berma nominal o zona de la berma de peu sobre la qual recolza el mantell principal, i (2) berma de sacrifici o zona de la berma de peu que protegeix la berma nominal. A partir del dany de la berma de peu nominal, es proposa un nou mètode per reduir el tamany de roca (Dn50) incrementant l'amplada de la berma (Bt) quan no es disposi de la mida requerit en pedrera. Finalment, s'examina el dany del mantell de cubs i s'analitza la influència del mètode de col¿locació sobre el mateix , a partir d'assajos realitzats amb mantells bicapa de cubs amb col¿locació aleatòria i uniforme.
Herrera Gamboa, MP. (2017). Mound Breakwater Design in Depth-Limited Breaking Wave Conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/82553
TESIS

Computer models are nowadays routinely used in harbor engineering applications. Models based on the two-dimensional elliptic mild-slope equation can simultaneously simulate refraction, diffraction, reflection, and dissipation in completely arbitrary coastal domains. However, floating structures such as floating breakwaters and docks are often encountered in the modeling domain. This makes the problem locally 3- dimensional. Hence it is problematic to incorporate a floating structure into the 2-d model. Tsay and Liu (1983) proposed a highly simplified but approximate approach to handle this problem practically. The validity of their approach is examined in detail and it is found that the actual solutions deviate considerably from the theoretical solutions, although their approximation provides results with the correct trend. Therefore, correction factors have been developed and may be used to produce more reliable results using the framework of Tsay and Liu (1983). The resulting method is applied to Douglas harbor in Alaska. The result shows that docks in the harbor distort the wave field considerably and create a reflective pattern that can affect navigation safety in some areas. Also plots are developed for the transmission coefficients for waves propagating past rectangular and cylindrical floating objects of infinite extent for a wide range of conditions encountered in practice.

Rock slope failures leading to rock falls and rock slides are caused by a multitude of factors, including seismic activity, weathering, frost wedging, groundwater and thermal stressing. Although these causes are generally attributed as separate causes, some of them will often act together to cause rock slope failures. In this work, two of the above factors, seepage of water through cracks and crack propagation due to the after effects of blasting are considered. Their combined impact on the development of rock falls and rock slides is modeled on ANSYS workbench using the Bingham Canyon mine slope failure of 2013 as a case study. Crack path modeling and slope stability analysis are used to show how a combination of crack propagation and seepage of water can lead to weakening of rock slopes and ultimate failure. Based on the work presented here, a simple approach for modeling the development of rock falls and rock slides due to crack propagation and seepage forces is proposed. It is shown how the information from remote sensing images can be used to develop crack propagation paths. The complete scope of this method involves demonstrating the combination of basic remote sensing techniques combined with numerical modeling on ANSYS workbench.

In May of 2000 Jason-1, a joint project between NASA and the French space agency CNES, will be launched. Its mission is to continue the highly successful gathering of data which TOPEX/Poseidon has collected since August of 1992. The main goal of Jason-1 is to achieve higher accuracy in measuring the mean sea level (MSL). In order to do so, the electromagnetic (EM) bias must be estimated more accurately because it is the largest contributing error. This thesis presents two different studies which add to the knowledge and improve estimation of the EM bias, and thus assists Jason-1 in achieving its primary goal. Oceanographic data collected from two different experiments are analyzed; on in the Gulf of Mexico (GME) and the other in Bass Strait, Australia (BSE). The first study is a spatial analysis of the backscattered power versus the phase of the wave. Its purpose is to determine why the normalized EM bias stops increasing and levels out at high wind speeds (about 11 m/s) and then decreases at higher wind speeds. Two possible causes are investigated. First, it could be due to a shift in the backscatter power modulation to the forward or rear face of the wave crests. Second, it may be due to the backscatter power becoming more homogeneous throughout the wave profile. This study is novel because it uses the knowledge of the spatial distribution of both the backscatter and wave displacement for the study of the EM bias. Both contribute to the EM bias decrease, but the latter cause seems to be the dominant effect. This study is performed on GME data. The second study uses two different nonparametric regression (NPR) techniques to estimate the EM bias. A recent study of satellite data from the TOPEX/Poseidon altimeter supports that the bias is modeled better using NPR regression. A traditional parametric fit is compared to two NPR techniques with GME data. The parametric fit is a variation of NASA's equation used to estimate EM bias for their Geophysical Data Records (GDRs). The two NPR techniques used are the Nadaraya-Watson Regression (NWR) and Local Linear Regression (LLR) estimators. Two smoothing kernel functions are used with each NPR technique, namely the Gaussian and the Epanechnikov kernels. NPR methods essentially consist of statistically smoothing the measured EM bias estimates are compared in the wind and significant wave height plane. Another recent study has shown that wave slope is strongly correlated to EM bias. With this knowledge, EM bias is estimated over several two-dimensional planes which include wave slope in attempt to reduce the residual bias. This portion of the study is performed on GME and BSE data. It is shown that a combination of slope, significant wave height, and wind speed used in conjunction with these NPR methods produces the best EM bias estimate for tower data.

Restlöcher ausgekohlter Braunkohlentagebaue werden aus landeskulturellen und ökonomischen Gründen wasserwirtschaftlich als Speicher, Hochwasserrückhaltebecken, Klärteiche, Wassergewinnungsanlagen sowie zur Naherholung genutzt. Diese Restlöcher werden zum großen Teil von aus geschüttetem Abraum bestehenden Böschungen umschlossen. Bei Wasserspiegelschwankungen neigen diese unbefestigten Böschungen zum Rutschen. Als Folge dieser Böschungsrutschungen bilden sich auf der Wasseroberfläche Wellen, die eine beachtliche Größe erreichen können. Diese Schwallwellen übertreffen in ihren Ausmaßen die Windwellen in den Tagebaurestlöchern um ein Vielfaches. Um diese Erscheinungen vorausberechnen zu können, wurden im Hubert-Engels-Laboratorium der Sektion Wasserwesen Untersuchungen durchgeführt. Die Entwicklung einer allgemeingültigen Berechnungsmethode für die Schwallwelle bei der Bewegung eines Teiles der das Wasserbecken begrenzenden Böschung verlangt die Einführung erfassbarer Parameter wie der Breite der rutschenden Böschung, den zeitlichen Verlauf der Wasserverdrängung sowie Tiefen- und Lageverhältnisse des Beckens. Die dafür notwendigen Kennzahlen können nur näherungsweise bestimmt werden, so dass einfache Beckengeometrien, ein über die Rutschzeit gleich bleibender Verlauf der Wasserverdrängung und Erhaltung der Böschungskante einem Berechnungsverfahren zugrunde gelegt werden müssen. Für die Berechnung des Füllschwalles auf das ruhende Wasser sind einige Verfahren bekannt geworden, die auf eine gemeinsame Gleichung für die Berechnung der Schwallhöhe zurückzuführen sind. Für die ebene Ausbreitung des Füllschwalles über Ruhewasser ergeben sieh zwei prinzipielle Abflussmöglichkeiten: Auflösung in Wellen oder brandender Schwallkopf. Diese beiden Möglichkeiten sowie der Übergangsbereich werden durch FROUDE-zahlen festgelegt. Der Wellenkopf von Füllschwallwellen wird durch eine Einzelwelle gebildet. Die Rutschung einer Böschung wurde durch die gleichzeitige Horizontal- und Vertikalbewegung einer Platte nachgebildet. Die Bewegung der Platte, die entstehenden Wellen und die Kräfte auf Auflaufböschung wurden durch einen Oszillografen aufgezeichnet. Die Auswertung der Versuche ergab eine Übereinstimmung zwischen Messergebnissen und den Berechnungen nach den Gesetzen des Füllschwalls. Die sekundlich verdrängte Wassermenge pro Breiteneinheit und die Ruhewassertiefe bestimmen die entstehenden Schwallwellen. Ein Einfluss der vertikalen Bewegungskomponente ist im untersuchten Bereich nicht nachweisbar. Die dynamischen Kräfte auf die Abschlussböschung können durch den Impuls der Einzelwelle dargestellt werden. Die räumliche Ausbreitung der Schwallwellen wurde in einem Modell untersucht. Dabei wurde festgestellt, dass die größten Wellenhöhen in der Richtung der Bewegung der Platte auftreten, während die Wellenhöhen in seitlichen Ausbreitungsrichtungen kleiner sind. Berechnungsansätze für die maximale Wellenhöhe der front wurden ermittelt. Als Ergebnis wurde ein Berechnungsverfahren entwickelt, welches ausgehend von den Parametern dar Rutschung, die Eigenschaften der Schwallwellen einschließlich der durch sie hervorgerufenen Belastungen auf der Auflaufböschung ermöglicht. Mit diesem Berechnungsverfahren ist es möglich, Böschungen wirtschaftlich zu gestalten und schädliche Rückwirkungen auf das Staubecken durch Schwallwellen zu vermeiden. Bisher notwendige Kosten für eine sehr flache Gestaltung der Böschung können entfallen. Gleichzeitig bleibt ein größerer nutzbarer Stauraum erhalten. Die Digitalisierung der vorliegenden Arbeit durch die Sächsische Landesbibliothek - Staats- und Universitätsbibliothek Dresden (SLUB) wurde durch die Gesellschaft der Förderer des Hubert-Engels-Institutes für Wasserbau und Technische Hydromechanik an der Technischen Universität Dresden e.V. unterstützt.

Soft-rock coastal cliff retreat progresses by an intermittent and discontinuous series of slope mass movements, generally accepted to be concentrated during phases of strong wave attack or heavy rain. One of the fundamental limitations to improving understanding of these processes is a lack of accurate quantitative data on the hydrological and geotechnical behaviour of the cliff slope. In this study, high-resolution terrestrial surveys of coastal change over a fifteen year period have been analysed and combined with hydrological and geotechnical simulations of cliff behaviour under rainfall stress. The input parameters for the simulations have been established from site survey, cross-checked with data from a range of published literature. The numerical model has been applied to typical hydrological, climatic and geotechnical conditions at Covehithe, Suffolk. In addition, analyses of water levels and beach elevations have subsequently been included using archive observation data, to further investigate the mechanisms governing the nature of change at the study site. Key findings include: (a.) high-resolution modelling of rainfall-infiltration processes combined with slope stability analysis provides a unique insight into the complex interaction between slope morphology and dynamic hydrology in soft sea cliffs. (b.) detailed analysis of daily factors of safety related to specific daily rainfalls is significant in reproducing failure conditions at the study site, and elucidates the complex interaction between cliff stratigraphy, cliff hydrology and rainfall. (c.) The results of the water level and beach elevation analyses show that marine processes are significant to the generation of cliff instability, consistent with the field observations and with the Sunamura (1983) model. These findings suggest that the instability of soft sea-cliffs results from complex and interacting controls that require an approach utilising a fully integrated transient hydrology and slope stability modelling. These results have significant implications for current coastal management practice.

Le bruit sismique est l'oscillation continue de la Terre enregistrée à chaque station en l'absence de tremblement de terre. Il résulte de l'interaction entre l'atmosphère, les océans et la terre solide. Le signal dominant, appelé microséismes secondaires dans la bande de fréquences 0,1-0,3 Hz, a pour origine l'interaction non linéaire entre des ondes de gravité océaniques de même fréquence et de directions opposées. Les fluctuations de pression qui en résultent près de la surface de l'océan génèrent un signal sismique. Le signal dominant est constitué d'ondes de Rayleigh (R). Plusieurs études montrent également l'existence d'ondes de Love (L) mais le rapport d'amplitude L/R entre les ondes de Love et de Rayleigh varie en fonction de la zone étudiée. Le mécanisme de génération des ondes de Rayleigh dues à l'interaction de ces sources de bruit avec le fond marin est bien compris et modélisé. Cependant, le mécanisme de génération des ondes de Love reste mystérieux car une source dans l'océan ne peut pas générer de mouvement de cisaillement. Dans ce travail, nous montrons l'existence d'ondes de Rayleigh et Love enregistrées par le réseau de l'Alaska et de la Californie. Nous étudions ensuite l'effet de la pente océan-continentale sur l'amplitude du bruit sismique des microséismes secondaires et quantifions la conversion des ondes de Rayleigh et de Love. Pour ce faire, nous utilisons la méthode des éléments spectraux pour simuler numériquement le champ d'ondes sismiques dans les milieux 3D. L'objectif est de déterminer les facteurs qui ont une influence sur l'amplitude des ondes de Love enregistrées sur le continent dans la bande de fréquences 0,1-1 Hz. Ces facteurs sont a) l'épaisseur de l'océan, b) l'effet de site à la source, c) la présence d'une couche sédimentaire sous le fond océanique et d) l'angle de la pente océan-continent. Nous observons que des ondes de Love peuvent être générées à la frontière océan-continental, et que la variation de leur amplitude dépend de la fréquence. La plus forte amplitude des ondes de Love est enregistrée dans un modèle avec 6 km d'océan, 6 km de croûte et 10 km de manteau à des fréquences de résonance dans l'océan lorsque la source est loin de la côte. Cependant, à d'autres fréquences, les océans peu profonds et les sources proches de la frontière de la ocean-continent generent des ondes de Love d'amplitude maximale. En présence de sédiments, l'amplification de Love est plus élevée à des périodes plus courtes pour les deux sources. La réduction de l'angle de pente diminue l'amplitude de l'onde de Love. Pour les sources proches et éloignées de la frontière océan-continent, le rapport d'amplitude L/R varie fortement selon la fréquence et l'épaisseur de l'océan. Parmi tous les facteurs, les rapports d'amplitude L/R les plus élevés sont générés dans les sédiments lorsque la source est proche de la frontière
Seismic noise is the continuous oscillation of the Earth recorded at every station in the absence of earthquakes . The interaction of atmosphere, ocean waves and earth creates them. The dominant signal, called secondary microseisms in the frequency band 0.1-0.3 Hz have known to be formed due to the non-linear interaction between two oppositely traveling ocean gravity waves. The resulting pressure fluctuations close to the ocean surface generates a seismic signal which is dominantly Rayleigh waves (R). Many authors reported the observations of Love wave content (L) in the seismic signal. However the L/R amplitude ratio is shown to vary depending on the area investigated. The generation mechanism of Rayleigh waves due to these noise sources interacting with the sea-bottom is well understood and modeled. The explanation why Love waves are generated is unclear because the source in the ocean cannot generate shear motion. We have shown the existence of Rayleigh and Love waves recorded by the Alaska and California network. We then investigate the effect of ocean-continental slope boundary on the seismic noise amplitude of secondary microsiesm and quantify the Rayleigh-to-Love wave conversion. In order to do that, we use the spectral element method to numerically simulate the seismic wave field in 3D media. The primary focus of this study is on investigating several factors that can influence the seismic noise amplitude recorded on the continent in the frequency band 0.1-1 Hz. Those factors are a) the ocean-thickness, b) the source-site effect i.e., source close to the boundary and far from the boundary, c) the sedimentary layer beneath the sea-bottom and d) the effect of ocean-continental slope angle. We observe that Love waves can be generated at the ocean-continental boundary, however the amplitude change is frequency dependent. We observe energy in the transverse direction in a model that cannot generate Love waves as a result of conversion at the ocean-continental slope boundary. The strongest Love wave amplitude is recorded in a model with 6 km deep ocean at resonant frequencies in the ocean when the source is far from the coast. However at other frequencies, shallow oceans and source close to the boundary generates highest Love wave amplitude. In the presence of sediments, the amplification of Love waves is higher at shorter periods for both sources. The reduction in slope angle diminishes the Love wave amplitude. For both source close and far from the boundary, the L/R amplitude ratio vary strongly with frequency and ocean thickness. Among all the factors, highest L/R amplitude ratios are generated due to sediments when the source is close to the boundary

The MUSCL-Hancock finite volume method with different slope limiters has been analyzed in the context of a fast transient flow problem. A derivation and analysis of the axial forces inside a pipe system due to a flow transient is also performed. 

The following slope limiters were implemented and compared: MC, van Leer, van Albada, Minmod and Superbee. The comparison was based on the method's ability to calculate the forces due to a flow transient inside a pipe system.

The tests and comparisons in this thesis show that the MC, van Leer, van Albada and Minmod limiters behave very much the same for the flow transient problem. If one would rank these four limiters with respect to the numerical error, the order would be the one presented above, the MC limiter being the most accurate. The error the four limiters produce is mainly of diffusive nature and it is just the magnitude of the diffusion that seems to differ between the methods. One should also note that the workload rank of the four limiters is the same as the order presented above. The MC limiter being the least efficient of the four and the Minmod limiter the most efficient.

In most of the tests performed the Superbee limiter display a rather negative unpredictable behavior. For some relatively simple cases this particular approach shows big difficulties maintaining the dynamical properties of the force. However, the upside of the Superbee limiter is its remarkable ability to maintain the maximum value of the forces present in the pipe system, preventing underestimation of the maximum magnitude of the force.

[ES] El cambio climático y la conciencia social sobre el impacto de las infraestructuras en el medio está llevando a la necesidad de diseñar diques en talud con cotas de coronación reducidas frente a eventos de rebase más extremos. Además, la mayoría de estos diques se construyen en zonas de profundidades reducidas, donde el oleaje rompe a causa de la limitación por fondo. Estudios recientes apuntan a la necesidad de considerar no sólo la caudal medio de rebase (q) sino también el máximo volumen individual de rebase (Vmax), el espesor de lámina de agua (OLT) y la velocidad del flujo de rebase (OFV) en el diseño de la cota de coronación de un dique en talud según criterios de rebase. No obstante, existen pocos estudios en la literatura científica centrados en Vmax en estructuras costeras sometidas a oleaje limitado por fondo. Además, estos estudios proporcionan resultados contradictorios en relación a la influencia de la limitación por fondo del oleaje sobre Vmax. En cuanto a OLT y OFV, no se han encontrado estudios en la literatura científica que permitan su predicción en diques en talud. En esta tesis doctoral, se han realizado ensayos físicos 2D en diques en talud rebasables (0.3≤Rc/Hm0≤2.5) sin espaldón y con tres mantos principales (Cubípodo®-1L, cubo-2L y escollera-2L) sobre dos pendientes de fondo suaves (m=2% and 4%) en condiciones de oleaje limitado por fondo (0.2≤Hm0/h≤0.9). Vmax junto con q son las variables más recomendadas en la literatura científica para diseñar la cota de coronación de diques en talud según criterios de rebase. En el presente estudio, los mejores resultados en la estimación de Vmax*=Vmax/(gHm0T012) se han obtenido empleando la función de distribución Weibull de dos parámetros con un coeficiente de determinación R2=0.833. Durante la fase de diseño de un dique en talud, es necesario predecir q para calcular Vmax cuando se emplean los métodos dados en la literatura científica. Por tanto, se debe estimar q con fines de diseño si no se dispone de observaciones directas. En caso de emplear la red neuronal CLASH NN para estimar q (R2=0.636), la bondad de ajuste de la función de distribución Weibull de dos parámetros propuesta en esta tesis para predecir Vmax* es R2=0.617. Así, el ratio entre Vmax* medido y estimado cae dentro del rango de 1/2 a 2 (banda de confianza del 90%) cuando se emplea q estimado con CLASH NN. Los nuevos estimadores desarrollados en la presente disertación proporcionan resultados satisfactorios en la predicción de Vmax* con un método más simple que aquellos propuestos en la literatura científica. No se ha encontrado una influencia significativa de la pendiente de fondo ni de la limitación por fondo del oleaje sobre Vmax* en este estudio. OLT y OFV están directamente relacionados con la estabilidad hidráulica de la coronación del dique y la seguridad peatonal frente a rebase. Por tanto, se requiere estimar OLT y OFV en la coronación del dique para diseñar apropiadamente su cota de coronación empleando criterios de rebase. En este estudio, se han empleado redes neuronales para desarrollar nuevos estimadores explícitos que permiten predecir OLT y OFV superados por el 2% del oleaje incidente con un alto coeficiente de determinación (0.866≤R2≤0.867). El número de cifras significativas apropiado para los coeficientes experimentales de dichos estimadores se ha determinado en base a su variabilidad. El punto óptimo en el que las características del oleaje deben ser estimadas para predecir OLT y OFV se ha identificado a una distancia de 3h desde el pie de la estructura (siendo h la profundidad a pie de dique). La pendiente de fondo tiene influencia sobre OLT y OFV. Los valores más extremos de OLT y OFV se han descrito empleando las distribuciones Exponencial de un parámetro y Rayleigh, respectivamente, con resultados satisfactorios (0.803≤R2≤0.812).
[CA] El canvi climàtic i la consciència social sobre l'impacte de les infraestructures al medi està portant a la necessitat de dissenyar dics en talús amb cotes de coronació reduïdes front a esdeveniments d'ultrapassament més extrems. A més, la majoria dels dics es construeixen en zones amb profunditats reduïdes on l'onatge es trenca a causa de la limitació per fons. Estudis recents apunten a la necessitat de considerar no solament el cabal mitjà de sobrepasse (q) sinó també el màxim volum individual de sobrepasse (Vmax), l'espessor de la làmina d'aigua (OLT) i la velocitat del flux de sobrepasse (OFV) pel disseny de la cota de coronació d'un dic en talús segons criteris de sobrepasse. No obstant, existeixen pocs estudis a la literatura científica centrats en Vmax en estructures costeres sotmeses a onatge limitat per fons. Addicionalment, aquests estudis proporcionen resultats contradictoris en relació a la influència de la limitació per fons de l'onatge sobre Vmax. Quant a OLT i OFV, no s'han trobat estudis a la literatura científica que permeten la seua predicció a dics en talús. En aquesta tesi doctoral, s'han realitzat assajos físics 2D amb dics en talús amb sobrepassos rellevants (0.3≤Rc/Hm0≤2.5) sense espatlló i amb tres elements al mantell principal (Cubípode-1L, cubs-2L i esculleres-2L) ubicats sobre pendents de fons suaus (m=2% i 4%) en condicions d'onatge limitat pel fons (0.2≤Hm0/h≤0.9). Vmax conjuntament amb q són les variables més recomanades a la literatura científica per dissenyar la cota de coronació en dics en talús segons criteris d'ultrapassament. Al present estudi, els millors resultats en l'estimació de Vmax*=Vmax/(gHm0T012) s'han obtingut utilitzant la funció de distribució Weibull de dos paràmetres amb un elevat coeficient de determinació R2=0.833. Durant la fase de disseny d'un dic en talús, és necessari predir q per calcular Vmax quan s'utilitzen els mètodes donats a la literatura científica. Per tant, es deu estimar q amb fins de disseny si no es disposa d'observacions directes. Si s'aplica la xarxa neuronal de CLASH NN per estimar q (R2=0.636), la bondat d'ajust de la funció de distribució Weibull de dos paràmetres proposada a aquesta tesi per predir Vmax* és R2=0.617. Així doncs, el ràtio entre el Vmax* mesurat i estimat es troba dins del rang de 1/2 a 2 (banda de confiança del 90%) quan s'usa q predit amb CLASH NN. Els nous estimadors desenvolupats a aquesta dissertació proporcionen resultats satisfactoris en la predicció de Vmax* amb un mètode més senzill que aquells proposats a la literatura científica. No s'ha trobat una influència significativa de la pendent de fons ni de la limitació de l'onatge per fons sobre Vmax* a aquest estudi. OLT i OFV estan directament relacionats amb l'estabilitat hidràulica de la coronació de dics i la seguretat de vianants front a ultrapassaments. Per tant, es requereix estimar OLT i OFV en la coronació de dics per dissenyar apropiadament la seua cota de coronació utilitzant criteris de sobrepasse. En aquest estudi, s'han usat xarxes neuronals per desenvolupar nous estimadors explícits que permeten predir OLT i OFV superats pel 2% de l'onatge incident amb un elevat coeficient de determinació (0.866≤R2≤0.867). El nombre de xifres significatives apropiat per als coeficients experimentals dels mencionats estimadors s'ha determinat basant-se en la seua variabilitat. El punt òptim on determinar les característiques de l'onatge deuen ser estimades per predir OLT i OFV s'ha identificat a una distància de 3h des del peu de l'estructura (on h és la profunditat a peu de dic). La pendent de fons té influència sobre OLT i OFV. Els valors més extrems de OLT i OFV s'han descrit amb les distribucions Exponencial d'un paràmetre i Rayleigh, respectivament, amb resultats satisfactoris (0.803≤R2≤0.812).
[EN] Climate change and the social concern about the impact of infrastructures is leading to mound breakwaters with reduced crest freeboards facing higher extreme overtopping events. In addition, most mound breakwaters are built in the surf zone where depth-limited wave breaking takes place. Recent studies point out the need of considering not only the mean wave overtopping discharge (q) but also the maximum individual wave overtopping volume (Vmax), the overtopping layer thickness (OLT) and the overtopping flow velocity (OFV) when designing mound breakwater crest elevation using overtopping criteria. However, few studies in the literature are focused on Vmax on coastal structures under depth-limited breaking wave conditions. In addition, those few studies report contradictory conclusions regarding the significance of depth-limited breaking waves on Vmax. With respect to OLT and OFV, no studies are found in the literature for their prediction on mound breakwaters. In this PhD thesis, 2D physical model tests were conducted on overtopped mound breakwaters (0.3≤Rc/Hm0≤2.5) without a crown wall armored with three armor layers (Cubipod®-1L, cube-2L and rock-2L) on two gentle bottom slopes (m=2% and 4%) in depth-limited breaking wave conditions (0.2≤Hm0/h≤0.9). Vmax together with q are the most recommended variables in the literature to design mound breakwater crest elevation based on overtopping criteria. In the present study, the 2-parameter Weibull distribution provides the best results when estimating Vmax*=Vmax/(gHm0T012) with coefficient of determination R2=0.833. During the design phase of a mound breakwater, q is needed to predict Vmax using methods given in the literature. Thus, q must be estimated for design purposes when direct observations are not available. If CLASH NN is used to estimate q (R2=0.636), the goodness-of-fit of the 2-parameter Weibull distribution proposed in this thesis to predict Vmax* is R2=0.617. Hence, the ratio between the estimated and measured Vmax* falls within the range 1/2 to 2 (90% error band) when q is predicted using CLASH NN. The new estimators derived in this study provide satisfactory estimations of Vmax* with a method simpler than those found in the literature. Neither the bottom slope nor the depth-induced wave breaking seem to significantly influence the dimensionless Vmax* in this study. OLT and OFV are directly related to the hydraulic stability of the armored crest and the pedestrian safety. Thus, OLT and OFV are required to properly design crest elevation using overtopping criteria. Neural Networks (NNs) are used in this study to develop new explicit unbiased estimators for the OLT and OFV exceeded by 2% of the incoming waves with a high coefficient of determination (0.866≤R2≤0.867). The appropriate number of significant figures of the empirical coefficients of such estimators is selected according to their variability. The optimum point where wave characteristics are determined to predict OLT and OFV was identified at a distance of 3h from the toe of the structure (where h is the water depth at the toe of the structure). The bottom slope does influence both OLT and OFV. The most extreme values of OLT and OFV are described with the 1-parameter Exponential and Rayleigh distribution functions, respectively, with satisfactory results (0.803≤R2≤0.812).
Al Ministerio de Educación, Cultura y Deporte, por la financiación brindada con el programa de Formación de Profesorado Universitario (FPU16/05081). Al Ministerio de Economía y Competitividad, por la financiación de los proyectos ESBECO (EStabilidad hidráulica del manto, BErmas y COronación de diques en talud con rebase y rotura por fondo, BIA2015-70436-R) y HOLOBREAK (Estabilidad Hidráulica y Transmisión de Diques Rompeolas Homogéneos de Baja Cota Diseñados a Rotura por Fondo, RTI2018-101073-B-I00-AR).
Mares Nasarre, P. (2021). Overtopping flow on mound breakwaters under depth-limited breaking wave conditions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/163154
TESIS

La theorie des ondes longues en eau peu profonde est utilisee pour calculer plusieurs equations decrivant les ondes internes en fluide stratifie. On reformule l'equation de kdv et on calcule l'equation des ondes longues d'interface a fortes courbures. Une revue de synthese des etudes sur la generation des ondes internes par le passage de la maree sur le talus continental introduit notre etude theorique: les methodes de l'eau peu profonde generalisee nous permettent le calcul des ondes baroclines et barotropes, reflechies ou transmises lors de l'interaction de la maree avec le talus vertical. Nous etudions ensuite les ondes longues internes de grandes amplitudes. On etablit le role des conditions dites critiques sur l'existence d'ondes solitaires. Enfin on montre qu'en presence de courants moyens les caracteristiques (longueur d'onde, celerite,. . . ) des ondes longues d'interface sont qualitativement modifiees

L'activite economique maritime s'etant eloignee de la cote pour se rapprocher du bord du talus continental, les exploitants se trouvent confrontes a des mouvements baroclines qui peuvent etre de grandes amplitudes, les ondes longues internes. Dans ce memoire, on presente donc deux aspects concernant les ondes longues internes. Dans une premiere partie, la generation des ces ondes lors de l'interaction de la maree externe avec le talus continental a ete etudie. Il a ete montre grace a un modele lineaire d'ondes longues en bi-couche que l'incidence oblique de la maree ainsi que la rotation terrestre n'etaient pas a negliger. Le modele a ete valide en le comparant a des mesures in-situ realisees sur le malin shelf (ecosse). Dans la seconde partie, nous nous sommes interesses a l'interaction de ces ondes longues internes avec la houle de surface. En effet, sur les images sar, on peut observer la signature des ondes internes laissee en surface. Une premiere etude experimentale d'interaction entre une onde solitaire de surface et une onde courte monochromatique barotrope a ete menee simulant la difference d'echelle existant entre une onde longue interne et des vagues de vent. Des dephasages importants de l'onde courte ont ete mesures, en bon accord avec ceux predits par un modele theorique utilisant la technique wkb egalement presente dans ce memoire. Ce modele a aussi conduit a estimer les modulations d'amplitude de l'onde courte a travers la conservation de l'action d'onde mais ce point n'a pu etre teste experimentalement. Enfin, des experiences d'interaction entre une onde solitaire interne et une onde courte externe ont ete menees en milieu stratifie. Les modulations de la phase se sont averees trop faibles pour etre mesurees, et celles de l'amplitude ne sont pas decrites par la conservation de l'action d'onde etablie theoriquement pour le cas de la premiere serie d'experiences.

Nous etudions a l'aide de la theorie de l'eau peu profonde une onde interne plane dans le contexte d'un fluide tournant stratifie en bicouche. Differents cas ont ete traites pour lesquels les hypotheses de faible ecart de densite entre les couches et de faibles epaisseurs de couches sont considerees independamment ou en meme temps. Nous apportons la demonstration qu'une equation d'ostrovsky gouverne les ondes internes non-lineaires d'interface dans le cas faiblement tournant. Nous demontrons que reduire l'ecart de densite conduit a augmenter les effets de la rotation. Enfin nous etablissons les equations qui gouvernent les ondes internes dans quelques cas particuliers et nous donnons la forme de celle-ci. Des experiences ont ete menees dans la grande cuve tournante du laboratoire coriolis pour etudier l'influence de la rotation sur des ondes internes axisymetriques. Nous avons mis en evidence quelques phenomenes interessant et les conclusions experimentales confirment nos resultats analytiques en ce qui concerne les influences respectives de l'ecart de densite et de la rotation. La rotation modifie considerablement les lois d'evolution de l'amplitude en fonction de la distance au centre de la cuve. Une autre partie de l'etude a ete consacree a la recherche experimentale de la generation des ondes internes non-lineaires par la maree en presence du talus continental ainsi que leur propagation. L'originalite de ce travail reside dans la generation d'ondes internes tridimensionnelles ainsi que dans la prise en compte des effets de la rotation sur le mecanisme de generation et la propagation des ondes. Nous avons montre que seul le jusant engendre la maree interne sur le plateau et le talus. La rotation n'agit pas sur le mecanisme de generation mais sur la propagation des ondes, de plus elle en diminue l'amplitude et en augmente la vitesse de propagation.

Computer based numerical prediction of wave-body interactions has become a powerful design tool and is widely used in the offshore industry. Its application to wave energy conversion is more recent. The present work investigates the modelling of three configurations of sloped wave energy converters of increasing complexity using the boundary element method package WAMIT. These configurations are all related to the concept of the Sloped IPS buoy wave energy device. In order to understand and assess the validity of numerical modelling for the specific cases considered, a two stage procedure is adopted. The first stage is to check that the results obtained from WAMIT are consistent with its underlying theory. These results are then compared with the corresponding experimental data. The experimental equipment and methodology are described. This includes discussion of wave tanks, models, and measuring techniques. The three configurations of wave energy converter investigated are the following: (a) a single degree of freedom system whose power take-off is referenced to the sea bed; (b) a free floating device with no power take-off; and (c) a free floating device fitted wit a power take-off mechanism that uses water inertia for its reference.

Thesis (M.S. in Physical Oceanography) Naval Postgraduate School, March 1996.
"March 1996." Thesis advisor(s): Edward B. Thornton, Thomas C. Lippmann. Bibliography: p. 47-48. Also Available online.

An understanding of extreme waves is important in the design and analysis of offshore structures, such as oil and gas platforms. With the increase of interest in the shipping of LNG, the design of import and export terminals in coastal water of slowly varying intermediate depth requires accurate analysis of steep wave shoaling. In this thesis, data from laboratory experiments involving random wave simulations on very gentle slopes have been analysed in terms of a model of large wave events, and the results interpreted by observation of the shape and magnitude of the large wave events. The auto-correlation function of the free surface elevation time histories, called NewWave, has been calculated from the wave spectrum and shown to fit very well up to the point where waves start to break (when compared to the ‘linear’ surface elevation time history). It has been shown that NewWave is an appropriate model for the shape of the ‘linear’ part of large waves provided kd > 0.5. A Stokes-like expansion for NewWave analysis has been demonstrated to match the average shape of the largest waves, accounting for the dominant vertical asymmetry. Furthermore, an appropriate local wave period derived from NewWave has been inserted into a Miche-based limiting criterion, using the linear dispersion equation, to obtain estimates for the limiting wave height. Overall, the analysis confirms the Miche-type criterion applies to limiting wave height for waves passing over very mild bed slopes. A derivation of general Green-Naghdi (GN) theory, which incorporates non-linear terms in its formulation, is also presented. This approach satisfies the boundary conditions exactly and approximates the field equations. The derived 2-dimensional vertical GN Level 1 model, capable of simulating steep waves on varying water depth, is validated against solitary waves and their interactions, and solitary waves on varying water depth and gives good qualitative agreement against the KdV equation. The developed and validated numerical model is used to simulate focussed wave groups on both constant depth and gentle slope. In general, the behaviour of waves simulated by the numerical model is very similar to that observed in the experimental data. There is evidence of vertical asymmetry as the water depth is reduced, owing to the non-linearity. Although the main physics is still controlled by linear dispersion, the higher order harmonics become increasingly important for shoaling waves. The numerical results also show a slope-induced wave set-up that keeps on increasing in amplitude as the wave group travels on the gentle slope.

Many wave energy convertors are designed to use either vertical (heave) or horizontal (surge) movements of waves. But the frequency response of small heaving buoys and oscillating water column devices shows that they are too stiff and so their resonance is at too short a period. A device moving in the horizontal (surge) direction has less restoring spring and so its resonance is at too long a period. It follows that a device that moved at some intermediate slope angle could have an intermediate value of hydrodynamic stiffness and so be resonant at a variable and desirable part of the wave spectrum. There have been two series of model tests in this work. The first used a simple free-floating model with no power take-off apparatus and with constraint achieved by means of a large inertia plate lying in the slope plane. The second used a rig that constrained the slope movement of the buoy head by means of hydrostatic bearings running on a guide rod set to the chosen slope angle. An external power take-off system was used to simulate a linear damper for absorbing the incident wave energy and control the motion of the model. This thesis firstly studies the potential of varying the slope angle as a way of tuning the natural period of the device to suit useful wave periods. Secondly, it studies the experimental and theoretical power capture ability of models with different slope angles in regular waves in the frequency domain. The hydrodynamic coefficients of the model were determined both experimentally and numerically based on linear hydrodynamic concepts. The power absorption of the models was calculated using the experimental data of the hydrodynamic coefficients and also measured directly. Some control of power take-off was also investigated. Some irregular wave tests were carried out for the 45 degrees slope angle case. The results show that it is feasible to alter the slope angle of the device as a way of tuning its natural period. However, in further studies of the power capture ability for different slope angles, the device shows a very wide bandwidth and high efficiency performance when it is set to 45 degrees slope angle. This suggests that to constrain the device to a 45 degrees slope angle is suitable for most of the sea states.

Many wave energy convertors are designed to utilise either vertical (heave) or horizontal (surge) movements of waves. But the frequency response of small heaving buoys and oscillating water column devices shows that they are too stiff and so their resonance is at too short a period. A device moving in the horizontal (surge) direction has less restoring spring and so its resonance is at too long a period. It follows that a device that moved at some intermediate slope angle could have an intermediate value of hydrodynamic stiffness and so be resonant at a variable and desirable part of the wave spectrum. There have been two series of model tests in this work. The first used a simple free-floating model with no power take-off apparatus and with constraint achieved by means of a large inertia plate lying in the slope plane. The second used a rig that constrained the slope movement of the buoy head by means of hydrostatic bearings running on a guide rod set to the chosen slope angle. An external power take-off system was used to simulate a linear damper for absorbing the incident wave energy and control the motion of the model. The thesis firstly studies of the potentiality of varying the slope angle as a way of tuning the natural period of the device to suit wave conditions. Secondly, it studies of the experimental and theoretic at power capture ability of models with different slope angles in regular waves in the frequency domain. The hydrodynamic coefficients of the model were determined both experimentally and numerically based on linear hydrodynamic concepts. The power absorptions of the models were calculated using the experimental data of the hydrodynamic coefficients and also measured directly. Some control of power take-off were also investigated. Some irregular wave tests were carried out for the 45 degrees slope angle case.

Developpement de methodes de mesure pour evaluer l'affaiblissement du massif par le tir, en comparant des talus non decoupes et des talus decoupes a la poudre noire, au cordeau detonant et au boudin de gel (methode plus performante, realisant une fissure qui protege le massif arriere). Etude theorique de l'effet dynamique des fronts d'ondes et de l'effet quasi-statique des gaz

The growth of microalgae has the potential to be extremely useful for the production of a wide range of products or for specific processes, such as capture and cycling of CO₂. The fast micro-algal growth rates and ability to grow on agriculturally poor land and in waste water means that bio-production using algae has many advantages over traditional agricultural processes for certain applications. The raceway pond is the most common reactor used for the growth of microalgae, due to low capital costs, low operating costs, higher energy efficiency, improved net energy recovery and ease of installation. Low carbon dioxide mass transfer, which limits algal growth and productivity, is currently one of the largest issues in photo bioreactors of all forms. The microalgae within these systems only obtain carbon from the dissolved inorganic carbon and hence sufficient carbon dioxide mass transfer is one of the most important design parameters for any photobioreactor. This is particularly evident in raceway ponds as they have a lower volumetric mass transfer rate than other photobioreactors and are typically mass transfer limited. [Please note: the full text of this thesis has been deferred until 30 September 2017]

Acoustic emission (AE) is a natural phenomenon that occurs when a solid is subjected to stress. These emissions are produced by all materials during pre failure. In soil, AE results from the release of energy as particles undergo small strains. If these emissions can be detected, then it becomes possible to develop an early warning system to predict slope failure. International research has shown that AE can be used to detect ground deformations earlier than traditional techniques, and thus it has a role to play in reducing risk to humans, property and in mitigating such risks. This thesis researches the design of a system to quantify the AE and calculate the distance to the deformation zone, and hence information on the mechanism of movement. The quantification of AE is derived from measuring the AE event rate, the output of which takes the form of a displacement rate. This is accurate to an order of magnitude, in line with current standards for classifying slope movements The system also demonstrates great sensitivity to changes within the displacement rate by an order of magnitude, making the technique suitable to remediation monitoring. Knowledge of the position of the shear surface is critical to the planning of cost effective stabllisation measures. This thesis details the development of a single sensor source location technique used to obtain the depth of a developing or existing shear surface within a slope. The active waveguide is used to reduce attenuation by taking advantage of the relatively low attenuation of metals such as steel. A method of source location based on the analysis of Lamb wave mode arrival times at a smgle sensor is summansed. An automatic approach to source location is demonstrated to locate a regular AE source to within one metre. Overall consideration is also given to field trials and towards the production of monitoring protocols for data analysis, and the implementation of necessary emergency/remediation plans.

Water waves generated by wind and ships; ebb tidal currents; water level fluctuations; and dredging impact sediment transport in shallow water of the lower Columbia River. Observations were made over a one-year period after sand dredged from the navigation channel was placed at three study sites in the Puget Island region, 46°15'N 123°25'W, Oregon and Washington. Sediment composition is fine to medium grained, low density dacitic volcanics with small percentages of pumice, heavy minerals, and basalt.

O conhecimento de zonas potencialmente instáveis no fundo do mar é de fundamental importância para o desenvolvimento das estruturas marinhas, pois permite posicionar estruturas offshore em áreas mais seguras, reduzindo-se possíveis danos, custos e eventual poluição ambiental. Nesse contexto, o objetivo do presente trabalho é investigar, através de uma abordagem analítico-numérica, a estabilidade de maciços submarinos submetidos ao carregamento cíclico da onda. O efeito das ondas de água sobre o leito submerso é descrito pela propagação de uma onda de pressão ao longo de sua superfície, empregando-se a teoria linear de Stokes. São considerados maciços com superfície superior horizontal e inclinada, constituídos por material coesivo (argilas) e material granular (areias). Em maciços constituídos por solos finos, a capacidade resistente do material é modelada pelo critério de Tresca não-homogêneo e a análise da estabilidade é desenvolvida em condição não drenada. Por outro lado, em leitos granulares, a resistência do meio depende explicitamente do valor da poropressão, sendo descrita classicamente pelo critério de Coulomb sem coesão. A análise de estabilidade é então desenvolvida em tensões efetivas e o gradiente de poropressão atua como uma força volumétrica sobre o esqueleto, caracterizando o modo de carregamento principal deste material. Em razão da tendência a se densificar quando submetido a um estado de tensões desviadoras cíclicas, ocorre, em geral, a acumulação de excesso de poropressão no maciço granular. Consequentemente, o acoplamento entre o comportamento do material e o carregamento cíclico tem fundamental importância sobre o cálculo do excesso de poropressão desenvolvido. Para determinação das forças de percolação, considera-se uma abordagem simplificada baseada na partição das deformações em contribuições reversível e irreversível, que permite desacoplar o cálculo da pressão intersticial induzida pela onda. Aplicando-se conceitos da teoria da Análise Limite é possível formular limites inferiores e superiores da máxima amplitude segura do carregamento da onda. Finalmente, os efeitos da declividade da superfície do leito e da espessura de camada de solo sobre a estabilidade são analisados.
The knowledge of potentially unstable areas on the seabed is of fundamental importance to the development of marine structures, because it allows to install offshore structures in safer areas, reducing possible damages, costs and eventual environmental pollution. In this context, the objective of the present work is to investigate the stability of submarine soil masses subjected to the wave cyclic loading through analytical-numerical approaches. The effect of water waves on the submerged bed is described by the propagation of a pressure wave along its surface, using the Stokes’s linear theory. Soil masses with horizontal and sloped upper surface, composed of cohesive material (clays) and granular materiais (sands) are considered in this study. In soil masses constituted of fine soil, the material strength capacity is modeled by the non-homogeneous Tresca criterion and the stability analysis is carried out in undrained condition. On the other hand, in granular beds, the strength explicitly depends on the pore pressure value, being classically described by the Coulomb criterion without cohesion. Then, the stability analysis is developed in effective stress and the pore pressure gradient acts as a volumetric force on the skeleton, characterizing the main charging mode of this material. Due to the tendency to densify when subjected to a cyclic deviatoric stress state occurs, in general, the build-up of pore pressure excess in the granular mass. Consequently, the coupling between the material behavior and the cyclic loading has fundamental importance in the calculation of the pore pressure excess generated. In order to define the seepage forces, a simplified approach based on the partition of deformations in reversible and irreversible contributions is considered, which allows to decouple the wave-induced pore pressure calculation. Applying the concepts of the limit analysis theory it is possible to formulate upper and lower boundaries of the maximum safe amplitude of the wave loading. Finally, the effects of the seabed surface steepness and of the soil layer thickness on the stability are analyzed.

碩士
國立中興大學
土木工程學系
85
This study is aimed to investigate the character of the wave shoaling and breaking criteria in the steep slope seabed by the mean of model experiment in a wave flume. About the slope of the seabed, we use 1/3 1/5 and 1/10,and we explore the reflection of steep slope seabed , wave forms, shoaling and breaking criteria. The results show that the shoaling area of the steep slope seabed is short,and there is reflection over the seabed. And we find that through the shoaling coefficient is effected by the reflection, the linear shoaling formula is still useful to describe the relationship between shoaling coefficient and relative water deep when the Ursell number is small than 30. When the range of theUrsell number from 30 to breaking point,the shoaling area of the steep seabed will be too short, and the wave will be breaking before fully shoaling. The shoaling wave height and breaking criteria are obviously lower than the ones of the condition of mild slope. We can find the relationship between the shoaling coefficient and relative water depth by regression analysis of the result of our experiment, and detect if the breaking criteria be suitable to apply to the steep slope seabed.

碩士
逢甲大學
水利工程與資源保育研究所
96
In this study, wave spectrum is used to describe the random waves in the real seas. Wave run-up is calculated on the sloping faces of smoothed and rough dikes, respectly, by splicing spectrum. Comparing the calculated values with the model testing data, a modified equation is regressed, to improve the calculated values of run-up on smoothed sloping dike. Besides, three different types (#240, #400, #800) of 3M scotch-brite pads are choosen to cover on the sloping face of dike as to imitate the rough surface of dike. According to Nikuradse’s definition and analysis sieve comparison table, the roughness factor are 0.063（#240）, 0.038 （#400）, and 0.015（#800）.Under action of same wave condition, run-up data are measured both on smooth and rough slope synchronously. The roughness reduction factor is then analyzed with the measured data. Finally, run-up equations for rough slope of dike are gained by modifying the equation for the smooth slope of dike with regard to roughness reduction factor. This practical computing model can be applied for engineering.

碩士
國立成功大學
水利及海洋工程學系碩博士班
98
In this study, a numerical model based on Complementary Mild Slope Equation (CMSE) proposed by Hsu et al. (2006) was developed to simulate wave transformation of irregular waves over a general finite seabed. The exponential function is used to cut the wave spectrum into several wave components waves. A combined energy coefficient is added in the governing equation to solve nonlinear wave shoaling, wave breaking, energy dissipation, and wave-wave interaction. Both of them takes into accounts the effect of the bottom slope and wave propagation direction, that the model is validated thought experimental data for regular and irregular wave propagation over sloping bottom. The numerical results have shown good agreement with results of laboratory experiments. The numerical results show that the model is capable of describing the wave energy dissipation in numerical calculation for the case of sinusoidal ripped seabed. The model is also applied to calculate irregular waves travelling over a submerged elliptic shoal on a sloping bottom. The comparison of plenary wave height variations demonstrates that the present model is able to produce irregular wave transformation over submerged structure including shoaling, refraction, diffraction, reflection, wave breaking and energy dissipation.

Tide-topography coupling is important for understanding surface-tide energy loss, the intermittency of internal tides, and the cascade of internal-tide energy from large to small scales. Although tide-topography coupling has been observed and modeled for 50 years, the identification of surface and internal tides over arbitrary topography has not been standardized. Here, we begin by examining five surface/internal-tide decompositions and find that only one is (i) consistent with the normal-mode description of tides over a flat bottom, (ii) produces a physically meaningful depth-structure of internal-tide energy flux, and (iii) results in an established expression for internal-tide generation. Next, we examine the expression for internal-tide generation and identify how it is influenced by remotely-generated shoaling internal tides. We show that internal-tide generation is subject to both resonance and intermittency, and can not always be predicted from isolated regional models. Lastly, we quantify internal-tide generation and scattering on the Oregon Continental slope. First, we derive a previously unpublished expression for inter-modal energy conversion. Then we evaluate it using observations and numerical simulations. We find that the surface tide generates internal tides, which propagate offshore; while at the same time, low-mode internal tides shoal on the slope, scatter, and drive turbulent mixing. These results suggest that internal tides are unlikely to survive reflection from continental slopes, and that continental margins play an important role in deep-ocean tidal-energy dissipation.
Graduation date: 2011

碩士
中興大學
土木工程學系所
95
The purpose of this paper is to investigate the wave transformation over slope sandy bottom. It mainly focuses on the effect of sandy seabed, slope of seabed, soil shear modulus, soil permeability, to the wave damping on the slope sandy bottom. The governing equations in this study are derived from Tsai and Chen (2002). They set a suitable time-dependent mild-slope equation for wave propagating over a poro-elastic seabed including properties of porosity, shear modulus, permeability, of the soil. In addition, this paper also considers the nonlinear shoaling correction coefficient proposed by Tsai et al. (2001). The research compares first the wave deformation of sandy seabed and impermeable seabed. The numerical results indicate that the wave attenuation on the coarse sand seabed is more obvious than on the fine sand one. While changing the soil shear modulus, the wave damping is more obvious when the value of soil shear modulus is bigger. In addition, changing soil penetrance, its value is bigger when the wave attenuation is larger.

碩士
國立成功大學
水利及海洋工程學系
84
Applying mild-slope equation with spectral method, the paper offers a model to calculate irregular wave deforming on a uniform sea bed slope. The calculating method is discribed as follows:First, divide a selected spectrum by a certain frequency interval and transfer them into component waves. Second, assume each component wave with the same wave breaking energy dissipation factor. Third, apply mild-slope equation to calculate wave height deformation of each component. Fourth, re- compose the wave components into a spectrum at specified water depth, then, utilize this spectrum to estimate the irregular wave height.By varying the values of energy dissipation factor and frequency interval, the paper discusses their influences on the calculating results. Meantime, the results compared to the experimental or computed data that were conducted by Sato et al.(1987), Isobe et al.(1988) and Watanabe et al.(1988).

碩士
國立臺灣海洋大學
河海工程學系
97
In Taiwan, the natural of coastal slope is vulnerable, and will be induced landslide of coastal slope by seasonal typhoons induced rainfall intensity and wave loading. Because the coastal structures located between land and sea, and the complex geological conditions, due to seabed instability or slope damage, usually caused by varying degrees of disaster damage in nearshore coastal areas. Most of past research is focus to explore the stability analysis of seabed. In general, the coastal stability of slope should be considering the wave, tidal and geological conditions. The purpose of this study is to evaluate the liquefaction range of the seabed by wave loading and the impact of slope stability at Taiwan sandy coastal areas. The numerical program of Geo-Studio develop by Calgary university is adopted to establish a 2-D analysis model used to simulate the landslide behaviors. The different slope geometric models, and different outside the marine environment and geological conditions are considered. Combined with the liquefaction potential evaluation method by Chen and Yang (1996) to obtain the region of seabed liquefaction potential, the numerical programs use to simulate the different tide induce liquefaction of slope stability analysis. The typhoon waves and the different relative density conditions were considered to evaluate the effect of tide range on the slope stability. And the effect parameter factors of seabed slope liquefaction stability were discussed to understand the influence of the seabed liquefaction to the coastal slope stability. It could be provided with the slope stability of coastal region and the reference of safety assessment of nearshore engineering practice.

博士
國立成功大學
水利及海洋工程學系碩博士班
92
Although numerous analytical models have been developed to investigate the obliquely incident wave transformation on gentle slope, very few researchers have considered the effect of bottom slope, and the tangential relationship between the direction of a water-particle velocity and the curved surface of a wave ray. In the present study, various aspects of the wave field, including wave deformation, refraction and shoaling has been investigated. Unlike in the previous studies, the effect of bottom slope on the wave propagation has been considered here, and the geometric characteristic of wave refraction is investigated. 　　The present study is based on linearized free surface boundary conditions in absence of wave breaking. In order to describe the effect of bottom slope, the physical quantities related to wave motion are cast in a perturbed series with the bottom slope as the parameter. With the wave-ray coordinate system, the water-particle velocity can be tangential to the curved surface of a wave ray. Accordingly, an explicit expression for the velocity potential is derived as a function of the bottom slope, perturbed to the second order in the Eulerian system. Afterwards, the parametric functions for the water-particle motion are obtained by using a linear transformation between the Eulerian system and the Lagrangian system. By using the parametric functions, the process of successive deformation of a wave profile, the breaking index, the fluid-particle trajectory, the spatial and temporal asymmetry of wave profile, and the variation of wave height have been obtained before the wave breaking occurs. 　　For the Lagrangian system, the wave characteristics, as discussed in the thesis, are derived as explicit solutions, and illustrated with a series of figures under different conditions of the wave steepness in deep water, such as, the water depth, the incident angle and the bottom slope. In order to correspond with the physical characteristic of wave refraction, all the wave characteristics are specially analyzed along the direction of wave rays. However, the bottom slope is observed to affect the wavenumber, the breaking index, the temporal asymmetry of the wave profile and the variation of wave height, which are therefore presented in second-order in terms of the perturbed expansion. The foregoing could not be accurately described using the first-order analytic models. 　　Since the phenomenon of wave breaking is not considered in this study, the present results are applicable for the wave field before the breaking takes place. In the non-breaking region, the theoretical restrictions can be conditionally satisfied for the present analytical model under bottom slope < 1/2. For a steeper bottom slope, the effect of the bottom slope terms can be reinforced, however, it becomes inadequate to expect the full effect of the bottom slope because of the weak nature of convergence of the perturbation series.

碩士
國立中山大學
海洋環境及工程學系研究所
99
Equipped with advanced field instruments in the past few decades, oceanographers have been able to comprehend some characteristics of the internal waves(IWs), such as the generation, propagation and energy dissipation, as well as to promote understanding in oceanography and marine ecology affected by IWs in the world ocean. Although surface gravity wave and internal wave are two of the most common natural phenomena in the ocean, the interaction between them has not been fully investigated, despite limited theoretical derivations in the literature, nor using laboratory experiments to verify the theory. A series of laboratory experiments were conducted at the National Sun Yen-sen University to study the waveform evolution of continuous IWs propagation on the flat bottom and across a trapezoidal obstacle. Surface waves were generated on a density stratified fluid system in a wave flume, from which IWs were induced indirectly to investigate their wave properties associated with their propagation . The experimental results are then used to determine the maximum depth which could be affected by surface waves in different wave conditions(wave height and period), as well as the amplitude of the IWs induced. The relationship between them are then presented in graphic form. Experiments were also conducted in uniform density and stratified fluid system with a trapezoidal obstacle. The results reveal that (1)long-period surface waves were susceptible to the interaction with the IWs in a stratified system, thus rendering wave height reduction, and (2)short-period surface waves interactions with their IWs counterparts was insignificant, hence yielded wave height similar to that in uniform density fluid system. Moreover, experiments were also conducted to study for long and short period IW propagated over pseudo slope-shelf(using trapezoidal obstacle). The results show that the variation in the IWs significantly affected the strength of internal hydraulic jump and vortices on the front slope and subsequent waveform inversion on the horizontal plateau. For IWs with short period, the horizontal distance on the plateau affected by the IWs was shirter and the total time of wave-topography interaction decreased.

碩士
國立成功大學
水利及海洋工程學系碩博士班
101
A numerical model was developed for simulating wave run-up after wave breaking over a sloping beach. This model is decoupled by the wave model of EEMSE (evolution equation for mild-slope equation) as well as the wave run-up model of LSWWE (linear shallow-water wave equations). Experimental data of Mase et al. (1984) and Hsu et al. (2012) were used to perform the regression analysis. The result lead to a regression formula which was applied as the input wave conditions for the prediction of wave run-up as LSWWE was used. The model was applied to simulate wave run-up for the cases of wave propagation are 1D sloping beach and 2D planar beach. Numerical results showed that the present model is capable of describing the dynamic process of wave run-up. It is found that the wave run-up increases with the decrease of beach slope. A case study was successfully performed at Dapengwan for practical applications.

碩士
國立成功大學
水利及海洋工程學系碩博士班
91
In this study, we apply mild slope equation with spectral method to simulate transformation of irregular waves, and add the energy coefficient into the governing equation in terms of energy flux to deal with nonlinear shoaling、wave breaking and wave-wave interaction. First, divide the significant wave spectrum into different numbers of component waves with different spectral methods. Then we simulate the transformation of irregular waves to investigate equal frequency space and exponential frequency space methods. Meanwhile, the validity of the present model in two-dimensional problem is verified through comparisons with the results of the SWAN model. Comparisons of measured data and numerical results indicate that exponential frequency space wave cutting method is better than equal frequency space wave cutting method. Using exponential frequency space wave cutting method to get 30 component waves has good ability and computational efficiency for simulation of wave height, period and spectrum shape.

碩士
國立成功大學
水利及海洋工程學系
88
Based on the time-dependent parabolic mild-slope equation, the curvilinear coordinate is used to form the appropriate boundary grid system for wave calculations. The governing equation subject to radiation boundary conditions is solved by alternative direction implicit (ADI) method. From the numerical calculation, the special shape of coastal boundary topography and the problem of wave transformations can be solved by the curvilinear governing equation. In comparison with the finite difference method of Cartesian coordinate, the present model can improve the accuracy of the calculation by adjusting the size of grid mesh and fitting the appropriate grid system for irregular boundaries. The predictions were compared with experimental data and analytical solutions for the cases of wave transformations and waves passing around the circular pile.