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Liu S.M.,Ocean University of China | Liu S.M.,Marine Innovation and Technology
Journal of Marine Systems | Year: 2014

Nutrient transport patterns in the Huanghe (Yellow River) were investigated using biogeochemical observations carried out during 2001-2011 to examine how nutrient transports were affected by water-sediment regulation events and their potential effects on the adjacent Bohai ecosystem. The concentrations and composition of nutrients in the Huanghe had an obvious change during the water-sediment regulation events, which increased dissolved nutrient transports with a similar amplitude like freshwater discharge, while amplified particulate nutrient transports. Dissolved inorganic nitrogen was the predominant species of total dissolved nitrogen. Particulate phosphorus was the major form of phosphorus affected by high content of suspended particulate matter. Phosphate represented 68% of total dissolved phosphorus. The BSi was 20% of the sum of BSi and dissolved silicate. Nutrient transport patterns highly depend on freshwater discharge. The regulation events have shifted the seasonal patterns of water and nutrient transports with high flow condition occurring at least two months prior to the normal peak flow. Abundant nutrients were transported to the coastal water and nutrient imbalance was aggravated, most likely resulting in strong impacts on the adjacent Bohai ecosystem. © 2014 Elsevier B.V. All rights reserved.

Aubault A.,Marine Innovation and Technology | Yeung R.W.,University of California at Berkeley
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2012

As high-speed ferry traffic is growing in near-shore areas, fuel efficiency of vessel operating in finite-depth waters becomes more critical. This can be achieved by introducing multi-hulls and minimizing the wave resistance by a proper configuration of the hulls. The wave resistance of thin-hulled vessels can be computed within Michell's theory. Based on this principle, Yeung et al. (2004) introduced a formulation of the interference wave resistance on multi-hull vessels in deep water, after linearization of the boundary conditions. The method is generalized to any water-depth in this paper. Havelock(1921) derived the wave resistance of a single-hull vessel in finite-depth water. An expression of the interaction resistance between two hulls in finite-depth waters is derived, using a distribution of Havelock sources on the hulls. It is shown that the interference resistance may be defined as a function of geometric variables and a length-based Froude number and depth-based Froude number. The effect of sub-criticality, criticality and supercriticality of depth-based Froude number on the interference resistance is explored. The computation of the total wave resistance of two hulls is extended to vessels with any number of hulls. The application of this solution method is demonstrated. With the use of the formulation, multi-hull designs are optimized with respect to the geometric distribution of hulls as well as forward speed and water depth. The design of multi-hull vessels illustrates how an optimized design is quickly obtained. Design decisions early in the design process can therefore be facilitated by this procedure. Copyright © 2012 by ASME.

Cermelli C.A.,Marine Innovation and Technology | Roddier D.G.,Principle Power Inc. | Weinstein A.,Principle Power Inc.
Offshore Technology Conference, Proceedings | Year: 2012

A discussion covers the implementation of a 2 Mw floating wind turbine prototype installed offshore Portugal in October 2011; synergies with offshore oil and gas platforms; project management strategy developed to implement the project on a fast-track and with local content requirements; operation results; and prototype testing and expansion into pre-commercial and commercial activities. This is an abstract of a paper presented at the Offshore Technology Conference 2012 (Houston, TX 4/30/2012-5/3/2012).

Forristall G.Z.,Forristall Ocean Eng. Inc. | Aubault A.,Marine Innovation and Technology
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014

Many measurements of hurricane waves have been made from deep water production facilities in the Gulf of Mexico. Measurements made on different sides of the platforms differ from one another and the incident wave field because the platforms diffract and radiate waves. For many purposes, we would like to know the incident wave field. Forristall and Aubault (OMAE2013-10860) used WAMIT diffraction calculations to successfully invert wave spectra measured under a TLP model in the Marin offshore basin. We have now used similar techniques to invert spectra measured at offshore platforms during Hurricanes Gustav and Ike. We do not have any measurements of the undisturbed wave spectra for testing the results. The tests were made by checking whether inverse calculations on all the gauges deployed at different locations on the platforms could produce the same undisturbed wave field. Wave directions are needed for the diffraction calculations. Information from the wave gauges can be used to find the directions by optimizing the agreement among the inverted power spectra. To perform the optimization, we varied both the mean direction and spreading at each spectral frequency. The rms difference between the inverted probe spectral densities was minimized at each spectral frequency. When spectra from four gauges on a platform are inverted, they agree reasonably well with each other. The average of the inverted significant wave heights is slightly lower than the average of the measured significant wave heights. But when spectra from pairs of the four probes are inverted, the results differ depending on which pair is used. This result implies that our inversion method cannot be used on data from platforms with two probes, and casts doubt on the accuracy of four probe inversions. Copyright © 2014 by ASME.

Nolte J.D.,University of Hawaii at Manoa | Nolte J.D.,Marine Innovation and Technology | Ertekin R.C.,University of Hawaii at Manoa
Journal of Renewable and Sustainable Energy | Year: 2014

We present the numerical modeling of a heaving, point-source wave energy conversion (WEC) device, previously tested by the University of Hawaii at Manoa. The WEC device converts the vertical heave displacements into a rotational motion to generate electrical power; the heave displacements converted are from the WEC system rising with the incoming waves relative to an anchoring system. Two anchoring methods of the WEC device are referred to as the single-body case (moored system) and double-body case (drogue anchored system). The numerical model performs hydrodynamic analysis in the time domain in irregular seas for the single-body or double-body case. We then compare the predictions with the available in-ocean experiments. The computer program written for this purpose solves for the individual body motion and predicts the WEC device's power production over the time series. Moreover, we present the results of the study that shows the effect of the device-damping characteristics and the size and the depth of operation of the drogue on wave-power predictions. © 2014 AIP Publishing LLC.

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