Oceanus.

v. 42, no. 1 (2000

Development of engineering tools to analyze and design flexible structures in open ocean environments

Methods to effectively predict system response in marine settings are critical in the engineering design process. The high energy ocean environment can subject structures to large wave and current forces, causing complex coupled motions and loads. This research focused on the development of effective methods to predict flexible system response and the structural integrity of marine High Density Polyethylene (HDPE) components. Numerical modeling tools were developed to analyze and design flexible structures in open ocean environments. Enhancements to the University of New Hampshire\u27s Aqua-FE finite element computer program were performed, including expansion of the element library to include spherical geometries and implementation of various hydrodynamic effects such as Stokes 2nd order waves and water velocity reduction due to component shadowing. Two case studies, involving laboratory and field experiments, were performed evaluating the software modifications and examining the response of flexible systems in various environmental conditions. Practical applications of the numerical model are presented, focusing on the design, analysis and deployment of a submerged grid mooring 10 km from Portsmouth, NH. The system was recovered after a seven year deployment and inspected. The numerical model proved to be a valuable engineering tool for investigating a system\u27s motion dynamics and mooring tension response in marine environments. High density polyethylene is a primary structural component for marine systems such as fish containment, wave attenuators and marine defense barrier systems. The fundamental engineering issues with the compliant HDPE material are associated with how the material changes its stiffness and strength depending upon the service life, load rate and temperature. Structural modeling techniques were developed to determine effective methods of analyzing marine systems constructed of HDPE. This included the investigation of the mechanical behavior of new and environmentally fatigued HDPE specimens, obtained from commercial fish farms, at different strain rates and validation of the modeling approach with laboratory experiments. The operational limits, loads and modes of a failure of the HDPE cage frame were estimated, providing valuable information on the survivability of these large, flexible systems in offshore environments

The Influence of Mechanical Circulation on Water Column Stability and Dissolved Oxygen in Stratified Lakes

Surface circulators have been used in wastewater and industrial lagoons for many years, but only recently have they been designed for lakes and reservoirs as a water quality management tool. Their relatively low capital investment and operational costs make them an attractive chemical free option for ameliorating the symptoms of eutrophication. Little research has been conducted on their effectiveness in impacting water quality. Today many lake managers are waiting for independent research on surface circulators\u27 performance before installing such systems. The Occoquan Reservoir was the primary site for a study conducted to examine the influence of surface circulation on water quality. Eight surface circulators were installed in the reservoir in 2006 in an effort to lower iron and manganese by increasing dissolved oxygen in the lower waters. Oxygen and temperature profiles were recorded at three main sampling sites from April through October 2007. These data were compared with historical data collected by the Occoquan Watershed Monitoring Laboratory (OWML) to determine the influence of circulator operation. Near field flow studies were conducted around one circulator using an acoustic doppler velocimeter (ADV). It was found that the circulators had significantly less influence on the temperature and dissolved oxygen of Occoquan Reservoir. This appeared to be contributed by the low circulation flow rates that were measured. A modeling effort was also conducted to simulate measured temperature and dissolved oxygen profiles through 2007. Since CE-QUAL-W2 does not explicitly contain a module to directly simulate surface circulation, the pump module was modified to transfer water from a discrete depth in the hypolimnion to the surface. After a satisfactory agreement between measured and simulated temperature and dissolved oxygen profiles was obtained, the unknown zero flow condition of the reservoir was studied. Next, a series of hypothetical lakes were simulated to explore the influence of various lake sizes, circulation flow rates, and intake depths on the temperature and dissolved oxygen distribution. It was found that the vertical temperature distribution was relatively easy to affect, and it responded to the physical mixing from the surface circulators in a conservative manner. The vertical dissolved oxygen distribution was harder to influence since it was controlled by many processes involving oxygen supply and demand in the water column and the sediments. A new approach for evaluating the circulator performance was developed based on the reduction in sediment area subjected to anoxic overlaying water. This reduction in anoxic sediment area is considered proportional to the reduction in iron and manganese to the lake, and would therefore represent a benefit to the water quality

A definition study of an Advanced Data Collection and Location System (ADCLS)

The technical and economic advantages of developing an Advanced Data Collection and Location System (ADCLS) to operate within the Earth Observation System (EOS) planned for Polar Platform, as a replacement and/or augmentation of the existing ARGOS data collection system were assessed. The cost/effectiveness of ADCLS with respect to ARGOS hinges on the traffic and quality of service demand of the future user constituency

Advanced Engineering Laboratory project summaries 1994

The Advanced Engineering Laboratory of the Woods Hole Oceanographic Institution is a development laboratory within the Applied Ocean Physics and Engineering Department. Its function is the development of oceanographic instrumentation to test developing theories in oceanography and to enhance current research projects in other disciplines within the community. This report summarizes recent and ongoing projects performed by members of this laboratory

Organic over-the-horizon targeting for the 2025 surface fleet

Please note that this activity was not conducted in accordance with Federal, DOD, and Navy Human Research Protection RegulationsAdversarial advances in the proliferation of anti-access/area-denial (A2/AD) techniques requires an innovative approach to the design of a maritime system of systems capable of detecting, classifying, and engaging targets in support of organic over-the-horizon (OTH) tactical offensive operations in the 2025–2030 timeframe. Using a systems engineering approach, this study considers manned and unmanned systems in an effort to develop an organic OTH targeting capability for U.S. Navy surface force structures of the future. Key attributes of this study include overall system requirements, limitations, operating area considerations, and issues of interoperability and compatibility. Multiple alternative system architectures are considered and analyzed for feasibility. The candidate architectures include such systems as unmanned aerial vehicles (UAVs), as well as prepositioned undersea and low-observable surface sensor and communication networks. These unmanned systems are expected to operate with high levels of autonomy and should be designed to provide or enhance surface warfare OTH targeting capabilities using emerging extended-range surface-to-surface weapons. This report presents the progress and results of the SEA-21A capstone project with the recommendation that the U.S. Navy explore the use of modestly-sized, network-centric UAVs to enhance the U.S. Navy’s ability to conduct surface-based OTH tactical offensive operations by 2025.http://archive.org/details/organicovertheho1094545933Approved for public release; distribution is unlimited

WireWall – a new approach to measuring coastal wave hazard

In the UK £150bn of assets and 4 million people are at risk from coastal flooding, whilst the construction of sea wall defence schemes typically cost at least £10,000 per linear meter. With reductions in public funding, rising sea level, changing storm conditions and 3200 km of coastal defences (i.e. about £3bn), cost savings are required that do not cause a reduction in flood resistance. The design of new coastal flood defences and the setting of tolerable hazard thresholds requires site-specific information of wave overtopping during storms of varying severity. By converting an existing wave measurement technology into a prototype overtopping monitoring system "WireWall", field observations of the wave-by-wave horizontal overtopping speeds and volumes were made at our case study site Crosby, in the North West of England. The new data quantify the wave overtopping conditions observed, which varied with the wind, waves and tide, allowing better understanding of how wave hazard at Crosby changes with the local conditions