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21	Variação temporal de zooplâncton da zona de arrebentação da Praia de Tramandaí - RS e observações laboratoriais do copépode Ctenocalanus vanus Avila, Tatiana Ramos January 2007 (has links) Com o objetivo de se conhecer a comunidade zooplanctônica da zona de arrebentação da Praia de Tramandaí – RS e identificar a variação sazonal das espécies e sua relação com os padrões de ventos e influências de massas de água, foram realizadas 24 amostragens com intervalo de quinze dias entre agosto de 2005 e agosto de 2006. Dados de temperatura do ar e da água, salinidade, velocidade do vento e direção do vento e da corrente de deriva foram obtidos no campo no momento de cada coleta. A concentração de clorofila-a foi obtida em laboratório, assim como a identificação e quantificação do zooplâncton e sua biomassa em peso seco. Copepoda foi o grupo mais diverso com maior importância representada pela espécie Temora turbinata, seguida de Acartia tonsa e Subeucalanus pileatus. O misidáceo Metamysidopsis elongata atlantica apresentou entre todos os taxa encontrados, a maior freqüência de ocorrência e abundância relativa, correspondendo a grande parte da biomassa em peso seco encontrada. Biomassa de zooplâncton e clorofila-a não apresentaram correlação significativa, apresentando picos de 96 mg.m-³ e 138 μg.L-¹, respectivamente. O copépode Ctenocalanus vanus, apesar de originário de Águas Subantárticas e Subtropicais foi freqüente na região de estudo e a falta de conhecimento sobre seu comportamento e exigências reprodutivas nos levou a realizar testes de laboratório que permitiram observar sua forma de desova e eclosão, assim como estimar valores de produção de ovos, pelotas fecais e náuplios em duas dietas diferentes. Assim os dados levantados servirão de base para novos estudos que permitam um maior entendimento dos processos que ocorrem na coluna d’água da Praia de Tramandaí - RS. / This article aims at the research of the zooplanktonic community of the Tramandaí Beach – RS surf zone and at the identification of the seasonal variation of the species; its relations with wind patterns and water mass influence. To reach such objective, 24 samplings were done between August 2005 and August 2006 at intervals of fifteen days. Data about air and water temperature, salinity, wind speed, drift current, and wind direction were collected in the field at the same time of each sampling. The chlorophyll-a concentration was measured in laboratory as well as the identification and quantification of the zooplankton and its dry biomass. Copepoda was the most diverse group. Temora turbinata was the most important species followed by Acartia tonsa and Subeucalanus pileatus. The Mysidacea Metamysidopsis elongata atlantica expressed the highest frequency of occurrence and relative abundance among all taxa, corresponding to a considerable part of the total dry biomass. Zooplankton biomass and chlorophyll-a did not present significant correlation. The highest concentrations found were 96 mg.m-³ and 138 μg.L-¹ respectively. In spite of being originated in Subtropical and sub-Antarctic waters, the copepod Ctenocalanus vanus was frequently found in the study area. Because of the lack of knowledge about their behaviour and reproductive requirements, we accomplished laboratorial tests which allowed the observation of their kind of spawning and hatching. It also allowed estimating at the number of eggs, fecal pellets and number of nauplius in two different diets. Such data is going to be the basis for new studies to provide a higher understanding of the processes occurring in the water column of Tramandaí Beach - RS Zooplâncton Copepoda Copépodes : Ctenocalanus vanus Tramandaí, Praia de (RS) Surf zone Tramandaí Beach Zooplankton Temora turbinata Ctenocalanus vanus
22	Nonlinear Bathymetry Inversion Based on Wave Property Estimation from Nearshore Video Imagery Yoo, Jeseon 14 November 2007 (has links) Video based remote sensing techniques are well suited to collect spatially resolved wave images in the surf zone with breaking waves and dynamic bathymetric changes. An advanced video-based depth inversion method is developed to remotely survey bathymetry in the surf zone. The present method involves image processing of original wave image sequences, wave property estimation based on linear feature extraction from the processed image sequences, and is combined with a nonlinear depth inversion model. The original wave image sequences are processed through video image frame differencing and directional low-pass filtering schemes to remove wave-breaking-induced foam noise having high frequencies in the surf zone. The features of individual crest trajectories are extracted from the processed and rectified image sequences, i.e. processed image cross-shore timestacks, by tracking pixels of high intensity within an interrogation window of a Radon-transform-based line-detection algorithm. The wave celerity is computed using space-time information of the extracted trajectories of individual wave crests in the cross-shore timestack domain. The presented retrieval of nearshore bathymetry from video image sequences is based on a nonlinear depth inversion using the nonlinear shallow water wave theory. The nonlinear wave amplitude dispersion effects at the breaker points are determined by combining the nonlinear shallow water celerity equation with a wave breaker criterion, thereby computing water depths iteratively from the celerity measured from the video data. The water depths estimated at the breaker points present initial bathymetric anchor points. Bathymetric profiles in the surf zone are inverted by calculating wave heights dissipated after wave breaking with a wave dissipation model and wave heights shoaled before wave breaking with a wave shoaling model. The continuous wave amplitude dispersion effects are subtracted from the measured celerity profiles, resulting in nearshore bathymetric profiles. The nonlinear depth inversion derived bathymetric estimates from nearshore imagery match the measured values with a biased mean depth error of about +0.06m in the depth range of 0.1 to 3m. In addition, the wave height estimates by the depth inversion model are comparable to the in-situ measured wave heights with a biased mean wave height error of about +0.14m. The present depth inversion method based on optical remote-sensing supports coastal management, navigation, and amphibious operations. Surf zone Wave breaking Wave celerity Nonlinear depth inversion Wave property estimation Video imagery Submarine topography Remote sensing Ocean waves Image processing Video recordings
23	Numerical modelling of turbulence and sediment concentrations under breaking waves using OpenFOAM® Brown, Scott Andrew January 2017 (has links) This thesis presents the development of a novel numerical model capable of evaluating suspended sediment dynamics under breaking waves, and is based in the open source Computational Fluid Dynamics software, OpenFOAM®. The hydrodynamics were determined by solving the incompressible, Reynolds-Averaged Navier-Stokes equations for a two-phase fluid using the Finite Volume method, along with a Volume of Fluid scheme that modelled the interface between the air and water phases. A new library of five turbulence models was developed to include weakly compressible effects through the introduction of density variations in the conservation equations. This library was thoroughly evaluated against existing physical data for surf zone dynamics. A skill score was applied, based on the MSE, to rank the models, with the nonlinear k−ε performing best overall, and the k−ω predicting turbulent kinetic energy most accurately. Furthermore, the numerical model was shown to predict the near-bed hydrodynamics well, through comparison with new in-house physical data obtained in the COAST laboratory. Suspended sediment concentrations were determined using an advection-diffusion methodology, with near-bed processes modelled using a flux based approach that balances entrainment and deposition. The model was validated against existing experimental data for steady state flow conditions, as well as for regular and breaking waves. The agreement was generally good, with the results indicating that the model is capable of capturing complicated processes such as sediment plumes under plunging breakers. The validated model was applied to investigate the properties of the sediment diffusivity, which is a vital parameter in suspended sediment dynamics. In physical experiments, sediment diffusivity is commonly estimated implicitly, based on the vertical concentration profile. In this work, this approach was applied to the numerical concentration predictions, and compared with the value directly determined within the model. The estimated value was generally acceptable providing that large horizontal concentration gradients were not present, and diffusion dominated flow advection. However, near the breaking point of waves, large errors were observed at mid-depth of the water column, which strongly correlates with a region of large flow advection relative to diffusion. Therefore, when using this estimation, caution is recommended since this approach can potentially lead to substantial discrepancies. 551.46
24	Etude numérique de la transformation des vagues en zone littorale, de la zone de levée aux zones de surf et de jet de rive Tissier, Marion 15 December 2011 (has links) Dans cette thèse, nous introduisons un nouveau modèle instationnaire de vagues valable de la zone de levée à la zone de jet de rive adapté à l'étude de la submersion. Le modèle est basé sur les équations de Serre Green-Naghdi (S-GN), dont l'application à la zone de surf reste un domaine de recherche ouvert. Nous proposons une nouvelle approche pour gérer le déferlement dans ce type de modèle, basée sur la représentation des fronts déferlés par des chocs. Cette approche a été utilisée avec succès pour les modèles basés sur les équations de Saint-Venant (SV) et permet une description simple et efficace du déferlement et des mouvements de la ligne d'eau. Dans ces travaux, nous cherchons à étendre le domaine de validité du modèle SV SURF-WB (Marche et al. 2007) vers la zone de levée en incluant les termes dispersifs propres aux équations de S-GN. Des basculements locaux vers les équations de SV au niveau des fronts permettent alors aux vagues de déferler et dissiper leur énergie. Le modèle obtenu, appelé SURF-GN, est validé à l'aide de données de laboratoire correspondant à différents types de vagues incidentes et de plages. Il est ensuite utilisé pour analyser la dynamique des fronts d'ondes longues de type tsunami en zone littorale. Nous montrons que SURF-GN peut décrire les différents types de fronts, d'ondulé non-déferlé à purement déferlé. Les conséquences de la transformation d'une onde de type tsunami en train d'ondulations lors de la propagation sur une plage sont ensuite considérées. Nous présentons finalement une étude de la célérité des vagues déferlées, basée sur les données de la campagne de mesure in-situ ECORS Truc-Vert 2008. L'influence des non-linéarités est en particulier quantifiée. / In this thesis, we introduce a new numerical model able to describe wave transformation from the shoaling to the swash zones, including overtopping. This model is based on Serre Green-Naghdi equations, which are the basic fully nonlinear Boussinesq-type equations. These equations can accurately describe wave dynamics prior to breaking, but their application to the surf zone usually requires the use of complex parameterizations. We propose a new approach to describe wave breaking in S-GN models, based on the representation of breaking wave fronts as shocks. This method has been successfully applied to the Nonlinear Shallow Water (NSW) equations, and allows for an easy treatment of wave breaking and shoreline motions. However, the NSW equations can only be applied after breaking. In this thesis, we aim at extending the validity domain of the NSW model SURF-WB (Marche et al. 2007) to the shoaling zone by adding the S-GN dispersive terms to the governing equations. Local switches to NSW equations are then performed in the vicinity of the breaking fronts, allowing for the waves to break and dissipate their energy. Extensive validations using laboratory data are presented. The new model, called SURF-GN, is then applied to study tsunami-like undular bore dynamics in the nearshore. The model ability to describe bore dynamics for a large range of Froude number is first demonstrated, and the effects of the bore transformation on wave run-up over a sloping beach are considered. We finally present an in-situ study of broken wave celerity, based on the ECORS-Truc Vert 2008 field experiment. In particular, we quantify the effects of non-linearities and evaluate the predictive ability of several non-linear celerity models. Zone de surf Théorie des chocs Schémas hybrides Franchissement Ressauts ondulés Célérité des vagues déferlées Fully non-linear Boussinesq type model Surf zone Shock theory Hybrid schemes Overtopping Undular bores Broken wave celerity
25	Oceanographic Considerations for the Management and Protection of Surfing Breaks Scarfe, Bradley Edward January 2008 (has links) Although the physical characteristics of surfing breaks are well described in the literature, there is little specific research on surfing and coastal management. Such research is required because coastal engineering has had significant impacts to surfing breaks, both positive and negative. Strategic planning and environmental impact assessment methods, a central tenet of integrated coastal zone management (ICZM), are recommended by this thesis to maximise surfing amenities. The research reported here identifies key oceanographic considerations required for ICZM around surfing breaks including: surfing wave parameters; surfing break components; relationship between surfer skill, surfing manoeuvre type and wave parameters; wind effects on waves; currents; geomorphic surfing break categorisation; beach-state and morphology; and offshore wave transformations. Key coastal activities that can have impacts to surfing breaks are identified. Environmental data types to consider during coastal studies around surfing breaks are presented and geographic information systems (GIS) are used to manage and interpret such information. To monitor surfing breaks, a shallow water multibeam echo sounding system was utilised and a RTK GPS water level correction and hydrographic GIS methodology developed. Including surfing in coastal management requires coastal engineering solutions that incorporate surfing. As an example, the efficacy of the artificial surfing reef (ASR) at Mount Maunganui, New Zealand, was evaluated. GIS, multibeam echo soundings, oceanographic measurements, photography, and wave modelling were all applied to monitor sea floor morphology around the reef. Results showed that the beach-state has more cellular circulation since the reef was installed, and a groin effect on the offshore bar was caused by the structure within the monitoring period, trapping sediment updrift and eroding sediment downdrift. No identifiable shoreline salient was observed. Landward of the reef, a scour hole ~3 times the surface area of the reef has formed. The current literature on ASRs has primarily focused on reef shape and its role in creating surfing waves. However, this study suggests that impacts to the offshore bar, beach-state, scour hole and surf zone hydrodynamics should all be included in future surfing reef designs. More real world reef studies, including ongoing monitoring of existing surfing reefs are required to validate theoretical concepts in the published literature. Aramoana Beach Dunedin (New Zealand) ArcGIS ArcSDE artificial surfing reef backscatter Baseline Data Collection bathymetry bathymetric surveying beach morphodynamics beach-state and morphology breaking wave height coastal engineering coastal environment coastal management coastal monitoring coastal processes coastal structures currents economic value EIA environmental data management environmental impact assessment geographic information systems geoid geomorphic surfing break categorisation GIS groin hydrodynamic modelling hydrographic surveying hydrography ICZM incline plane modelling integrated coastal zone management Main Beach Mount Maunganui (New Zealand) Manu Bay Boat Ramp Raglan (New Zealand) measuring water levels morphological coupling multibeam echo soundings oceanography offshore wave transformations Palm Beach Reefs Gold Coast (Australia) RTK GPS salient surf zone hydrodynamics surfing break components surfing reefs surfing tourism surfing wave climate surfing wave parameters Tay Street Mount Maunganui (New Zealand) wave breaking intensity wave climate wave focusing wave modelling wave peel angle wave section length wind effects on waves

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