758 research outputs found

    Projecting Climate Dependent Coastal Flood Risk With a Hybrid Statistical Dynamical Model

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    ABSTRACT: Numerical models for tides, storm surge, and wave runup have demonstrated ability to accurately define spatially varying flood surfaces. However these models are typically too computationally expensive to dynamically simulate the full parameter space of future oceanographic, atmospheric, and hydrologic conditions that will constructively compound in the nearshore to cause both extreme event and nuisance flooding during the 21st century. A surrogate modeling framework of waves, winds, and tides is developed in this study to efficiently predict spatially varying nearshore and estuarine water levels contingent on any combination of offshore forcing conditions. The surrogate models are coupled with a time-dependent stochastic climate emulator that provides efficient downscaling for hypothetical iterations of offshore conditions. Together, the hybrid statistical-dynamical framework can assess present day and future coastal flood risk, including the chronological characteristics of individual flood and wave-induced dune overtopping events and their changes into the future. The framework is demonstrated at Naval Base Coronado in San Diego, CA, utilizing the regional Coastal Storm Modeling System (CoSMoS; composed of Delft3D and XBeach) as the dynamic simulator and Gaussian process regression as the surrogate modeling tool. Validation of the framework uses both in-situ tide gauge observations within San Diego Bay, and a nearshore cross-shore array deployment of pressure sensors in the open beach surf zone. The framework reveals the relative influence of large-scale climate variability on future coastal flood resilience metrics relevant to the management of an open coast artificial berm, as well as the stochastic nature of future total water levels.This work was funded by the Strategic Environmental Research Development Program (DOD/SERDP RC-2644). Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. F. J. Mendez, A. Rueda, and L. Cagigal acknowledge the partial funding from the Spanish Ministry of Science and Innovation, project Beach4cast PID2019-107053RB-I00. The authors thank the Scripps Center for Coastal Studies for their efforts to deploy, recover, and process surf zone pressure sensor data used as validation in this study. The authors thank Melisa Menendez for sharing GOW2 hindcast data for Southern California. The authors thank the sea-level rise projection authors for developing and making the sea-level rise projections available, multiple funding agencies for supporting the development of the projections, and the NASA Sea-Level Change Team for developing and hosting the IPCC AR6 Sea-Level Projection Tool

    High Frequency Radar Wind Turbine Interference Community Working Group Report

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    Land-based High Frequency (HF) Radars provide critically important observations of the coastal ocean that will be adversely affected by the spinning blades of utility-scale wind turbines. Pathways to mitigate the interference of turbines on HF radar observations exist for small number of turbines; however, a greatly increased pace of research is required to understand how to minimize the complex interference patterns that will be caused by the large arrays of turbines planned for the U.S. outer continental shelf. To support the U.S.’s operational and scientific needs, HF radars must be able to collect high-quality measurements of the ocean’s surface inand around areas with significant numbers of wind turbines. This is a solvable problem, but given the rapid pace of wind energy development, immediate action is needed to ensure that HF radar wind turbine interference mitigation efforts keep pace with the planned build out of turbines

    Comparative performance of a novel oscillating water column wave energy converter

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    This thesis presents research which shows that a helically configured Oscillating Water Column (OWC) could deliver improved performance compared to a conventional tube OWC, whilst saving a significant amount of draft. It is anticipated that savings in the deployment costs for this compact machine will outweigh any additional manufacturing costs. In order to prove the benefits of the helical concept, its performance relative to a conventional plain tube OWC was investigated in detail using scaled physical models. These models evolved during the course of the study, and refined models were developed. A variable impedance turbine simulator was also developed to test the models at their optimum conditions. The tests themselves were also refined leading to a high degree of confidence in the final result. A mathematical model was also adapted to model the performance of the physical models, and to help understand the physical processes involved in the system. With this series of improving physical models and tests, it has been shown that it is possible to achieve a 27% reduction in draft, with a 24% increase in power output

    Aaltoenergiavoimalaitoksen sähkötehontuottoyksikön testilaitteen suunnittelu

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    Wave energy means producing electricity from ocean waves. After decades of reseach, and a multitude of prototype devices installed, this renewable energy source is still globally untapped, despite its high energy production potential. One of the design challenges in wave energy converters is the marine environment. Installing and testing devices in their actual domain is difficult and expensive. To mitigate this, the devices must be tested on dry land before deployment. Simulations and small scale experiments are vital in this process, but can only go so far. Especially, the product development of a hydraulic power take-off unit without a full scale test device is almost impossible. This work presents the test bench of a wave energy converter called WaveRoller, and proposes a new control algorithm for the test bench. The test bench is used in the power take-off unit product development and the commercialization of the wave energy converter. In its task, it has been a vital help. 350 kW marine version of the wave energy converter and its power take-off module developed using the test bench is under construction, and will be commissioned in Peniche, Portugal during 2017. The findings of this thesis will be used to further refine the test bench, and the improved test bench will be used to develop new models of power take-off units.Aaltoenergialla tarkoitetaan sähkön tuottamista meren aaltoliikkeestä. Vuosikymmenten tutkimuksen ja monien testilaitteiden jälkeen tämä uusiutuvan energian muoto on maailmanlaajuisesti vielä hyödyntämättä, huolimatta korkeasta potentiaalisesta energiantuotantokapasiteetista. Eräs merkittävä aaltoenergian suunnitteluhaaste on meriympäristö. Laitteiden asennus ja testaus oikeassa toimintaympäristössään on vaikeaa ja kallista. Tämän vuoksi laitteita tulee testata mahdollisimman pitkälle kuivalla maalla. Simulaatioilla ja pienen mittakaavan testeillä voidaan päästä pitkälle, mutta etenkin hydraulisen sähkötehontuotantoyksikön tuotekehitys on lähes mahdotonta ilman täyden mittakaavan koelaitetta. Tämä työ esittelee WaveRoller-nimisen aaltoenergiavoimalaitoksen sähköntuotantoyksikön täysikokoisen koelaitteen testipenkin, ja kehittää sitä varten uuden säätöalgoritmin. Testipenkin tarkoitus on auttaa aaltoenergiavoimalaitoksen tuotekehityksessä. Testipenkin tulee mallintaa mahdollisimman tarkasti voimia, joita aallot aiheuttavat laitteeseen, ja tässä tehtävästä se suoriutuu hyvin. 350 kW:n mereen asennettava versio sähkötehontuottoyksiköstä on rakenteilla, ja se tullaan asentamaan 2017 Portugalin Penicheen. Tämän työn löydöksiä tullaan hyödyntämään uusien laitemallien suunnittelussa

    Selected Papers from the 2018 IEEE International Workshop on Metrology for the Sea

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    This Special Issue is devoted to recent developments in instrumentation and measurement techniques applied to the marine field. ¶The sea is the medium that has allowed people to travel from one continent to another using vessels, even today despite the use of aircraft. It has also been acting as a great reservoir and source of food for all living beings. However, for many generations, it served as a landfill for depositing conventional and nuclear wastes, especially in its deep seabeds, and we are assisting in a race to exploit minerals and resources, different from foods, encompassed in it. Its health is a great challenge for the survival of all humanity since it is one of the most important environmental components targeted by global warming. ¶ As everyone may know, measuring is a step that generates substantial knowledge about a phenomenon or an asset, which is the basis for proposing correct solutions and making proper decisions. However, measurements in the sea environment pose unique difficulties and opportunities, which is made clear from the research results presented in this Special Issue

    Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation

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    Abstract. The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including RPAS (remotely piloted aircraft systems) observations, allowed us to detect the presence of rip currents and rip channels at the mouth of Sele River, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment analysis and a set of high-resolution wave numerical simulations, completed with Google EarthTM images and RPAS observations. The grain size trend analysis and the numerical simulations allowed us to identify the rip current occurrence, forced by topographically constrained channels incised on the seabed, which were compared with observations
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