Hamilton Jr. R.P.,Woods Hole Group Inc.
Hydro International | Year: 2011
Woods Hole Group, headquartered in Falmouth, Massachusetts, is an international environmental scientific and engineering consultancy focused on water and sediment from the deep ocean through the coastal zone. Scientific and engineering expertise includes: Oceanography & Measurement Systems; Coastal Sciences, Engineering & Planning; and Environmental Assessment & Remediation. Source
Magnell B.A.,Woods Hole Group Inc. |
Gordon L.,Doppler Ltd. |
Yamin H.,Tadiran Batteries Ltd.
2015 IEEE/OES 11th Current, Waves and Turbulence Measurement, CWTM 2015 | Year: 2015
Ocean deployments of battery-powered instruments often include lithium battery packs, which enable deployments to last three times as long as they would using alkaline battery packs. Lithium batteries are widely regarded as hazardous. When we discovered that one of our ADCPs, which had been deployed with lithium batteries, had flooded, we worried whether the result would pose a risk. What we found was that while the ADCP's electronics had irreparably corroded, the batteries had discharged but had not gotten particularly hot, and not much else had happened. This paper explains why things happen slowly in these lithium batteries, even when they are immersed in conductive sea water. The slow rate of discharge of these particular batteries prevents them from getting very hot in such circumstances. We conclude that these lithium batteries are probably not more dangerous than alkaline batteries, given appropriate venting of the pressure housing. © 2015 IEEE. Source
Llort-Pujol G.,Telecom Bretagne |
Sintes C.,Telecom Bretagne |
Chonavel T.,Telecom Bretagne |
Morrison III A.T.,Woods Hole Group Inc. |
Daniel S.,Laval University
Marine Technology Society Journal | Year: 2012
Current high-resolution sidescan and multibeam sonars produce very large data sets. However, conventional interferometry-based bathymetry algorithms underestimate the potential information of such soundings, generally because they use small baselines to avoid phase ambiguity. Moreover, these algorithms limit the triangulation capabilities of multibeam echosounders (MBES) to the detection of one sample per beam, i.e., the zero-phase instant. In this paper, we argue that the correlation between signals plays a very important role in the exploration of a remotely observed scene. In the case of multibeam sonars, capabilities can be improved by using the interferometric signal as a continuous quantity. This allows consideration of many more useful soundings per beam and enriches understanding of the environment. To this end, continuous interferometry detection is compared here, from a statistical perspective, first with conventional interferometry-based algorithms and then with high-resolution methods such as the Multiple Signal Classification (MUSIC) algorithm. We demonstrate that a well-designed interferometry algorithm based on a coherence error model and an optimal array configuration permits a reduction in the number of beam formings (and therefore the computational cost) and an improvement in target detection (such as ship mooring cables or masts). A possible interferometry processing algorithm based on the complex correlation between received signals is tested on both sidescan sonars and MBESs and shows promising results for detection of small in-water targets. Source
Dill N.L.,Woods Hole Group Inc.
Proceedings of the International Conference on Estuarine and Coastal Modeling | Year: 2012
Numerical modeling provides an efficient tool for simulating hydrodynamics in estuarine environments. It is particularly useful when extensive field data collection is impractical, or when impacts of proposed restoration or engineering alternatives must be evaluated. Often surface water flow within an estuarine system is controlled by hydraulic structures such as culverts, flap gates, weirs, and/or sluice gates. These types of structures typically require special treatment within hydrodynamic model codes due to spatial scale limitations and/or physical assumptions (e.g., free surface flow). The Environmental Fluid Dynamics Code (EFDC) provides a means to model hydraulic structures using withdrawal-return pairs of model grid cells. However, the application of withdrawal-return cells in an EFDC model requires a priori knowledge of the relationship between water level and flow rate for the particular structure (e.g. a head-discharge relationship, rating curve, look-up table). In many cases it is difficult or impractical to obtain this information. The flow regime (e.g., outlet control, inlet control, pressure flow) may change as well. To remedy this, additional subroutines have been implemented within the EFDC code to compute discharge through various types of flow control structures (e.g., pipe culverts, box culverts, sluice gates, flap gates). Flow rate is determined at each model time step based on the computed water surface elevation using standard engineering equations for the particular structure. The modeler is required to input the geometry of the structure (e.g., pipe length and diameter) and discharge coefficients or friction factors. There is no need to determine a head-discharge relationship for the structure a priori. Flux between the assigned withdrawal-return cells is accounted for using the original code, which maintains the conservation of mass and other scalar variables. Application of the additional subroutines is demonstrated using EFDC models of actual estuarine systems and validated using field observations. © 2013 American Society of Civil Engineers. Source
Ivanov L.I.,Woods Hole Group Inc. |
Magnell B.A.,Woods Hole Group Inc.
OCEANS 2012 MTS/IEEE: Harnessing the Power of the Ocean | Year: 2012
Strong currents are a matter of great concern for the maritime industries in the Gulf of Mexico. Oil industry operators working in the gulf are required to measure ocean current profiles and transmit these data in near-real-time. The data are collected primarily using TRDI ADCPs mounted on the structures or nearby. The individual data ensembles are sent to NDBC where they are processed, quality checked, archived and made available to the public through the NDBC website. In 2011, Woods Hole Group Inc. (WHG) was contracted by DeepStar Technology Development for Deepwater Research to create a database of deep ocean currents for the Gulf of Mexico. One of the objectives of the project was to identify and make plots of strong current ('energetic') events. WHG performed a thorough inspection of the data, including a review of the temporal and spatial continuity of the data, cross-check between neighboring stations and between current data and satellite altimetry charts. Based on this extensive dataset, a total of 560 strong current events were identified and classified according to the candidate mechanisms that cause these current intensifications. © 2012 IEEE. Source