Wave Energy Prize MASK wave calibration data for the 1:20 scale testing at MASK

DOE Data Explorer

Driscoll, Rick

2017-05-08

Time series data, sensor layout, and wave calibration summaries for the wave height measurements for the 10 calibration sea states for the 1:20 scale testing of the Wave Energy Prize (WEP) at the US Navy's Maneuvering and Seakeeping (MASK) Basin at the Naval Surface Warfare Center in Carderock, Maryland. Measurements were made in the test area and upstream of the test area.

Motion and Seasickness of Fast Warships

DTIC Science & Technology

2004-10-01

Motion and Seasickness of Fast Warships Riola J.M. (1), Esteban S. (2), Giron-Sierra J.M. (2) & Aranda J. (3) (1) Canal de Experiencias ...5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Canal de Experiencias Hidrodinámicas de ...Bretschneider Sp bability Density of Waves /λ, with H being the wave height (twice the wave a in a seakeeping basin Canal de Experiencias Hid r waves with

Open-Water Resistance and Seakeeping Characteristics of Ships with Icebreaking Bows

DTIC Science & Technology

1991-05-13

of a Knuckled Forefoot on a Typical Icebreaker ...... ................... . 19 3-2. Lines Plan, T-AGS OCEAN (ICE) . * * .... . 23 3-3. Curve of...the ice. As the stem strikes the ice, initial failure of the ice occurs by simple crushing. Then the raked stem of the icebreaker rides up onto the ice...bossings, skegs, rudders, 18 and special stem forefoot shapes were not included in the shapes tested. To ensure that the parent and its variants

Model-Scale Experiment of the Seakeeping Performance for R/V Melville, Model 5720

DTIC Science & Technology

2012-07-01

Angle 1 Y None Deg Sensor Bourns Rotary Potentiometer 6574S-1-103 NA 39596 KVH Sin 2 Y None volts Sensor KVH Fluxgate Compass C-100...NA Deg Sensor KVH Calc Heading NA N None DegM Calculated KVH Fluxgate Compass C-100 39449 Bow Tracker Sensor Bottom NA N None...3DM-3XI combined three axis of angular rate gyros, accelerometers, and magnetometers to provide various combinations of gyro stabilized Euler

T-Craft Seabase Ramp Loads Model Test Data Report

DTIC Science & Technology

2010-12-01

INTRODUCTION 1 TEST CONDITION MATRIX 2 MODEL DESCRIPTIONS 9 LMSR Model 15 Ramp Models 17 MODEL TEST SETUP 18 Side-by-Side Hull Configuration 19... INTRODUCTION The Office of Naval Research (ONR) sponsored a multiple bodied seakeeping model test designed to investigate vessel motions and loads on the hinge...C. 3. Side-by-Side configuration 137 Ramp Load cell 1.88 27.49 -CG ft I ^ -Hinged Connection 3.00 from CL to jauge • oad ce LMSR

Characterization of Regular Wave, Irregular Wave, and Large-Amplitude Wave Group Kinematics in an Experimental Basin

DTIC Science & Technology

2011-02-01

seakeeping was the transient wave technique, developed analytically by Davis and Zarnick (1964). At the David Taylor Model Basin, Davis and Zarnick, and...Gersten and Johnson (1969) applied the transient wave technique to regular wave model experiments for heave and pitch, at zero forward speed. These...tests demonstrated a potential reduction by an order of magnitude of the total necessary testing time. The transient wave technique was also applied to

ShipMo3D Version 1.0 User Manual for Frequency Domain Analysis of Ship Seakeeping in a Seaway

DTIC Science & Technology

2007-11-01

Atlantic TM 2007-171 ; R & D pour la défense Canada – Atlantique ; novembre 2007. Introduction : ShipMo3D est une bibliothèque orientée objet dotée...12 9 Inputs for Rudder Autopilot . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10 Inputs for Ship Motion Predictions in...DRDC Atlantic TM 2007-171 13 10 Inputs for Ship Motion Predictions in Random Seas This section gives background information that is useful when running

VSP - Discussion: The Common Interest on Planning Hulls and Plan for Collaboration Studies between NSWC and KRISO - Washington DC

DTIC Science & Technology

2016-03-07

planning hulls and plan for N62909-15-1-2052 collaboration studies between NSWC and KRISO - Washington DC Sb. GRANT NUMBER N62909-15-1-2052 Sc. PROGRAM...be carried out in MASK’s facilities. We discussed common interests on planing hulls , and made plans for collaboration studies between NSWC and KRISO... hull forms for satisfying the requirements of the project. Model tests and analyses are required to assess the maneuvering and seakeeping performance

Numerical simulation of vessel dynamics in manoeuvrability and seakeeping problems

NASA Astrophysics Data System (ADS)

Blishchik, A. E.; Taranov, A. E.

2018-05-01

This paper deals with some examples of numerical modelling for ship's dynamics problems and data comparison with corresponding experimental results. It was considered two kinds of simulation: self-propelled turning motion of crude carrier KVLCC2 and changing position of container carrier S 175 due to wave loadings. Mesh generation and calculation were made in STAR-CCM+ package. URANS equations were used as system of equations closed by k-w SST turbulence model. The vessel had several degrees of freedom, which depend on task. Based on the results of this research, the conclusion was made concerning the applicability of used numerical methods.

Review of ship slamming loads and responses

NASA Astrophysics Data System (ADS)

Wang, Shan; Guedes Soares, C.

2017-12-01

The paper presents an overview of studies of slamming on ship structures. This work focuses on the hull slamming, which is one of the most important types of slamming problems to be considered in the ship design process and the assessment of the ship safety. There are three main research aspects related to the hull slamming phenomenon, a) where and how often a slamming event occurs, b) slamming load prediction and c) structural response due to slamming loads. The approaches used in each aspect are reviewed and commented, together with the presentation of some typical results. The methodology, which combines the seakeeping analysis and slamming load prediction, is discussed for the global analysis of the hull slamming of a ship in waves. Some physical phenomena during the slamming event are discussed also. Recommendations for the future research and developments are made.

The Evaluation of Cone Capsule as an Alternative Hull form for Portable Tsunami Lifeboat to Support Evacuation System in the Coastal Regions and Small Islands

NASA Astrophysics Data System (ADS)

Fauzan Zakki, Ahmad; Suharto; Windyandari, Aulia

2018-03-01

Several attempts have been made to reduce the risk of tsunami disasters such as the development of early warning systems, evacuation procedures training, coastal protection and coastal spatial planning. Although many efforts to mitigate the impact of the tsunami in Indonesia was made, no one has developed a portable disaster rescue vehicle/shelter as well as a lifeboat on ships and offshore building, which is always available when a disaster occurs. The aim of the paper is to evaluate the performance of cone capsule shaped hull form that would be used for the portable tsunami lifeboat. The investigation of the boat resistance, intact stability, and seakeeping characteristics was made. The numerical analysis results indicate that the cone capsule is reliable as an alternative hull form for the portable tsunami lifeboat.

Measuring ocean waves from space; Proceedings of the Symposium, Johns Hopkins University, Laurel, MD, Apr. 15-17, 1986

NASA Technical Reports Server (NTRS)

Beal, Robert C. (Editor)

1987-01-01

Papers are presented on ocean-wave prediction; the quasi-universal form of the spectra of wind-generated gravity waves at different stages of their development; the limitations of the spectral measurements and observations of the group structure of surface waves; the effect of swell on the growth of wind wave; operational wave forecasting; ocean-wave models, and seakeeping using directional wave spectra. Consideration is given to microwave measurements of the ocean-wave directional spectra; SIR research; estimating wave energy spectra from SAR imagery, with the radar ocean-wave spectrometer, and SIR-B; the wave-measurement capabilities of the surface contour radar and the airborne oceanographic lidar; and SIR-B ocean-wave enhancement with fast-Fourier transform techniques. Topics discussed include wave-current interaction; the design and applicability of Spectrasat; the need for a global wave monitoring system; the age and source of ocean swell observed in Hurricane Josephine; and the use of satellite technology for insulin treatment.

Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves

NASA Astrophysics Data System (ADS)

Liu, Shukui; Papanikolaou, Apostolos D.

2011-03-01

Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT) of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.

Numerical simulation of the wave-induced non-linear bending moment of ships

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, J.; Wang, Z.; Gu, X.

1995-12-31

Ships traveling in moderate or rough seas may experience non-linear bending moments due to flare effect and slamming loads. The numerical simulation of the total wave-induced bending moment contributed from both the wave frequency component induced by wave forces and the high frequency whipping component induced by slamming actions is very important in predicting the responses and ensuring the safety of the ship in rough seas. The time simulation is also useful for the reliability analysis of ship girder strength. The present paper discusses four different methods of the numerical simulation of wave-induced non-linear vertical bending moment of ships recentlymore » developed in CSSRC, including the hydroelastic integral-differential method (HID), the hydroelastic differential analysis method (HDA), the combined seakeeping and structural forced vibration method (CSFV), and the modified CSFV method (MCSFV). Numerical predictions are compared with the experimental results obtained from the elastic ship model test of S-175 container ship in regular and irregular waves presented by Watanabe Ueno and Sawada (1989).« less

Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm.

PubMed

Liang, Lihua; Yuan, Jia; Zhang, Songtao; Zhao, Peng

2018-01-01

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller.

Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm

PubMed Central

Liang, Lihua; Zhang, Songtao; Zhao, Peng

2018-01-01

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller. PMID:29709008

Mathematical model of small water-plane area twin-hull and application in marine simulator

NASA Astrophysics Data System (ADS)

Zhang, Xiufeng; Lyu, Zhenwang; Yin, Yong; Jin, Yicheng

2013-09-01

Small water-plane area twin-hull (SWATH) has drawn the attention of many researchers due to its good sea-keeping ability. In this paper, MMG's idea of separation was used to perform SWATH movement modeling and simulation; respectively the forces and moment of SWATH were divided into bare hull, propeller, rudder at the fluid hydrodynamics, etc. Wake coefficient at the propellers which reduces thrust coefficient, and rudder mutual interference forces among the hull and propeller, for the calculation of SWATH, were all considered. The fourth-order Runge-Kutta method of integration was used by solving differential equations, in order to get SWATH's movement states. As an example, a turning test at full speed and full starboard rudder of `Seagull' craft is shown. The simulation results show the SWATH's regular pattern and trend of motion. It verifies the correctness of the mathematical model of the turning movement. The SWATH's mathematical model is applied to marine simulator in order to train the pilots or seamen, or safety assessment for ocean engineering project. Lastly, the full mission navigation simulating system (FMNSS) was determined to be a successful virtual reality technology application sample in the field of navigation simulation.

Dynamic response of Hovercraft lift fans

NASA Astrophysics Data System (ADS)

Moran, D. D.

1981-08-01

Hovercraft lift fans are subjected to varying back pressure due to wave action and craft motions when these vehicles are operating in a seaway. The oscillatory back pressure causes the fans to perform dynamically, exhibiting a hysteresis type of response and a corresponding degradation in mean performance. Since Hovercraft motions are influenced by variations in lift fan pressure and discharge, it is important to understand completely the nature of the dynamic performance of lift fans in order to completely solve the Hovercraft seakeeping problem. The present study was performed to determine and classify the instabilities encountered in a centrifugal fan operating against time-varying back pressure. A model-scale experiment was developed in which the fan discharge was directed into a flow-measuring device, terminating in a rotating valve which produced an oscillatory back pressure superimposed upon a mean aerodynamic resistance. Pressure and local velocity were measured as functions of time at several locations in the fan volute. The measurements permitted the identification of rotating (or propagating) stall in the impeller. One cell and two cell configurations were classified and the transient condition connecting these two configurations was observed. The mechanisms which lead to rotating stall in a centrifugal compressor are presented and discussed with specific reference to Hovercraft applications.

Numerical evaluation of longitudinal motions of Wigley hulls advancing in waves by using Bessho form translating-pulsating source Green'S function

NASA Astrophysics Data System (ADS)

Xiao, Wenbin; Dong, Wencai

2016-06-01

In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green's function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green's function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption.

Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model’s Motions and Loads Measurement in Realistic Sea Waves

PubMed Central

Jiao, Jialong; Ren, Huilong; Adenya, Christiaan Adika; Chen, Chaohe

2017-01-01

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship’s navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign. PMID:29109379

Floating Classroom Outreach as an Introduction to Ocean Studies

NASA Astrophysics Data System (ADS)

McFadden, M.

2016-02-01

Many children and young adults living within only one hour of the coast never have the opportunity to explore a beach or go out on a boat because of financial challenges or lack of transportation.These types of experiences are the spark that helped many ocean scientists become fascinated with the ocean and later pursue a career related to the ocean. This presentation will discuss a variety of outreach projects and the efficacy of each. Projects vary in age, complexity and cost. These projects include a Beach Clean-Up open to students and their families at a community college organized by a campus volunteer group with a focus on social issues, a Marine Biology and Physical Oceanography class joint floating classroom trip open to college students to introduce non-STEM students to marine science in an exciting setting, and an education outreach trip for 8-12 years old children from the Boys and Girls Club in Newport, RI in collaboration with The International SeaKeepers Society, a non-profit that facilitates ocean research and education by working closely with the yachting community. Emphasis on environmental education in the U.S. has grown considerably over recent years, and the development of unique and innovative approaches to hands-on marine science education are needed to excite students to explore the marine environment and care about environmental stewardship.

A Tale of Two Inlets: Tidal Currents at Two Adjacent Inlets in the Indian River Lagoon

NASA Astrophysics Data System (ADS)

Webb, B. M.; Weaver, R. J.

2012-12-01

The tidal currents and hydrography at two adjacent inlets of the Indian River Lagoon estuary (Florida) were recently measured using a personal watercraft-based coastal profiling system. Although the two inlets—Sebastian Inlet and Port Canaveral Inlet—are separated by only 60 km, their characteristics and dynamics are quite unique. While Sebastian Inlet is a shallow (~4 m), curved inlet with a free connection to the estuary, Port Canaveral Inlet is dominated by a deep (~13 m), straight ship channel and has limited connectivity to the Banana River through a sector gate lock. Underway measurements of tidal currents were obtained using a bottom tracking acoustic Doppler current profiler; vertical casts of hydrography were obtained with a conductivity-temperature-depth profiling instrument; and continuous underway measurements of surface water hydrography were made using a Portable SeaKeeper system. Survey transects were performed to elucidate the along-channel variability of tidal flows, which appears to be significant in the presence of channel curvature. Ebb and flood tidal currents in Sebastian Inlet routinely exceeded 2.5 m/s from the surface to the bed, and an appreciable phase lag exists between tidal stage and current magnitude. The tidal currents at Port Canaveral Inlet were much smaller (~0.2 m/s) and appeared to be sensitive to meteorological forcing during the study period. Although the lagoon has free connections to the ocean 145 km to the north and 45 km to the south, Sebastian Inlet likely drains much of the lagoon to its north, an area of ~550 sq. km.

Concept design and hydrodynamic optimization of an innovative SWATH USV by CFD methods

NASA Astrophysics Data System (ADS)

Brizzolara, Stefano; Curtin, Tom; Bovio, Marco; Vernengo, Giuliano

2012-02-01

The paper presents the main characteristics of an innovative platform which has been conceived and designed to extend the operational capabilities of current unmanned surface vehicles in terms of platform stability in waves and of powering requirement at a relatively high speed. The main idea which rules the project is the realization of a small autonomous surface unit (about 6 m in length) capable of undertaking several tasks in the marine environment even with moderate rough sea conditions. The designed vessel has the ability to locate, recover, and launch other members of the autonomous fleet (like AUVs or other underwater devices) and at the same time could carry out a surveillance service of the surrounding areas. To manage these tasks, the vehicle is designed to provide a fairly good autonomy which is needed to face intermediate-range missions (100 nautical miles). The choice of a small waterplane area twin hull (SWATH) form has been motivated by its excellent properties of seakeeping qualities, combined with a non-conventional low resistance underwater hull shape, currently under patenting process, which is able to reduce to a minimum the resistance of the vessel especially at higher speeds. To obtain the most efficient profile of the underwater bodies, a systematic optimization with an automatic procedure based on a parametric definition of the geometry, a state-of-the-art computational fluid dynamics (CFD) flow solver, and a differential evolution global minimization algorithm have been created and used. As expected, all the final CFD computations on the best design have demonstrated the superior efficiency of the developed unconventional SWATH technology with respect to different alternatives of current hull typologies.

Influence of motion coupling and nonlinear effects on parametric roll for a floating production storage and offloading platform.

PubMed

Greco, M; Lugni, C; Faltinsen, O M

2015-01-28

Occurrence and features of parametric roll (PR) on a weather-vaning floating production storage and offloading (FPSO) platform with a turret single-point mooring-line system are examined. The main focus is on the relevance of motions coupling and nonlinear effects on this phenomenon and on more general unstable conditions as well as on the occurrence and severity of water on deck. This work was motivated by recent experiments on an FPSO model without mooring systems highlighting the occurrence of parametric resonance owing to roll-yaw coupling. A three-dimensional numerical hybrid potential-flow seakeeping solver was able to capture this behaviour. The same method, extended to include the mooring lines, is adopted here to investigate the platform behaviour for different incident wavelengths, steepnesses, headings, locations of the turret and pretensions. From the results, sway and yaw tend to destabilize the system, also bringing chaotic features. The sway-roll-yaw coupling widens the existence region of PR resonance and increases PR severity; it also results in a larger amount of shipped water, especially at smaller wavelength-to-ship length ratio and larger steepness. The chaotic features are excited when a sufficiently large yaw amplitude is reached. Consistently, a simplified stability analysis showed the relevance of nonlinear-restoring coefficients, first those connected with the sway-yaw coupling then those associated with the roll-yaw coupling, both destabilizing. From the stability analysis, the system is unstable for all longitudinal locations of the turret and pre-tensions examined, but the instability weakens as the turret is moved forward, and the pre-tension is increased. The use of a suitable dynamic-positioning system can control the horizontal motions, avoiding the instability. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Influence of motion coupling and nonlinear effects on parametric roll for a floating production storage and offloading platform

PubMed Central

Greco, M.; Lugni, C.; Faltinsen, O. M.

2015-01-01

Occurrence and features of parametric roll (PR) on a weather-vaning floating production storage and offloading (FPSO) platform with a turret single-point mooring-line system are examined. The main focus is on the relevance of motions coupling and nonlinear effects on this phenomenon and on more general unstable conditions as well as on the occurrence and severity of water on deck. This work was motivated by recent experiments on an FPSO model without mooring systems highlighting the occurrence of parametric resonance owing to roll–yaw coupling. A three-dimensional numerical hybrid potential-flow seakeeping solver was able to capture this behaviour. The same method, extended to include the mooring lines, is adopted here to investigate the platform behaviour for different incident wavelengths, steepnesses, headings, locations of the turret and pretensions. From the results, sway and yaw tend to destabilize the system, also bringing chaotic features. The sway–roll–yaw coupling widens the existence region of PR resonance and increases PR severity; it also results in a larger amount of shipped water, especially at smaller wavelength-to-ship length ratio and larger steepness. The chaotic features are excited when a sufficiently large yaw amplitude is reached. Consistently, a simplified stability analysis showed the relevance of nonlinear-restoring coefficients, first those connected with the sway–yaw coupling then those associated with the roll–yaw coupling, both destabilizing. From the stability analysis, the system is unstable for all longitudinal locations of the turret and pre-tensions examined, but the instability weakens as the turret is moved forward, and the pre-tension is increased. The use of a suitable dynamic-positioning system can control the horizontal motions, avoiding the instability. PMID:25512590

Sustainable Oceanographic Vessels - Setting an Example

NASA Astrophysics Data System (ADS)

van Leer, J. C.

2009-12-01

In response to climate change, global warming and post “peak oil” fuel scarcity, the oceanographic community should consider reducing its carbon foot print. Why should scientists operate inefficient vessels while lecturing the general public on the need to reduce CO2 emissions? We have already seen curtailment of ship schedules and ship lay-ups, due in part to rising fuel costs, following $140/barrel crude oil. When the global recession ends, upward pressure on oil prices will again commence. Who can forecast how high fuel prices may ultimately rise during the typical 25-30 year lifetime of a research vessel? Are we to curtail future work at sea when oceanic climate research is becoming ever more important? A catamaran research vessel has been designed which can be electrically propelled from by a combination of high efficiency generators, photovoltaic panels and/or sails. Sail produced power is transformed with propellers and motor/generators into electric power which is stored in battery banks. This vessel could operate as the first true hybrid oceanographic research vessel. It could even continue operations without fuel in cases of a severe fuel shortage or fueling denial. Since the power produced by any water turbine increases with the cube of the velocity flowing over its propeller, the low fluid friction and high stability of a catamaran, with reasonably slender hulls, provide an important boost to efficient hybrid operation. The author has chartered a 42’ hybrid catamaran sailboat and found it efficient and extremely easy to operate and control. A 79’ motor sailing catamaran research vessel by Lock Crowther Designs will be presented as one example of a sustainable research vessel with excellent speed and sea-keeping. A center well makes operation as a small drilling/coring ship for coastal climate investigation possible. The center well also supports a host of remote sensing and robotic gear handling capabilities.

Numerical and experimental results on the spectral wave transfer in finite depth

NASA Astrophysics Data System (ADS)

Benassai, Guido

2016-04-01

Determination of the form of the one-dimensional surface gravity wave spectrum in water of finite depth is important for many scientific and engineering applications. Spectral parameters of deep water and intermediate depth waves serve as input data for the design of all coastal structures and for the description of many coastal processes. Moreover, the wave spectra are given as an input for the response and seakeeping calculations of high speed vessels in extreme sea conditions and for reliable calculations of the amount of energy to be extracted by wave energy converters (WEC). Available data on finite depth spectral form is generally extrapolated from parametric forms applicable in deep water (e.g., JONSWAP) [Hasselmann et al., 1973; Mitsuyasu et al., 1980; Kahma, 1981; Donelan et al., 1992; Zakharov, 2005). The present paper gives a contribution in this field through the validation of the offshore energy spectra transfer from given spectral forms through the measurement of inshore wave heights and spectra. The wave spectra on deep water were recorded offshore Ponza by the Wave Measurement Network (Piscopia et al.,2002). The field regressions between the spectral parameters, fp and the nondimensional energy with the fetch length were evaluated for fetch-limited sea conditions. These regressions gave the values of the spectral parameters for the site of interest. The offshore wave spectra were transfered from the measurement station offshore Ponza to a site located offshore the Gulf of Salerno. The offshore local wave spectra so obtained were transfered on the coastline with the TMA model (Bouws et al., 1985). Finally the numerical results, in terms of significant wave heights, were compared with the wave data recorded by a meteo-oceanographic station owned by Naples Hydrographic Office on the coastline of Salerno in 9m depth. Some considerations about the wave energy to be potentially extracted by Wave Energy Converters were done and the results were discussed.

Simulation of upwind maneuvering of a sailing yacht

NASA Astrophysics Data System (ADS)

Harris, Daniel Hartrick

A time domain maneuvering simulation of an IACC class yacht suitable for the analysis of unsteady upwind sailing including tacking is presented. The simulation considers motions in six degrees of freedom. The hydrodynamic and aerodynamic loads are calculated primarily with unsteady potential theory supplemented by empirical viscous models. The hydrodynamic model includes the effects of incident waves. Control of the rudder is provided by a simple rate feedback autopilot which is augmented with open loop additions to mimic human steering. The hydrodynamic models are based on the superposition of force components. These components fall into two groups, those which the yacht will experience in calm water, and those due to incident waves. The calm water loads are further divided into zero Froude number, or "double body" maneuvering loads, hydrostatic loads, gravitational loads, free surface radiation loads, and viscous/residual loads. The maneuvering loads are calculated with an unsteady panel code which treats the instantaneous geometry of the yacht below the undisturbed free surface. The free surface radiation loads are calculated via convolution of impulse response functions derived from seakeeping strip theory. The viscous/residual loads are based upon empirical estimates. The aerodynamic model consists primarily of a database of steady state sail coefficients. These coefficients treat the individual contributions to the total sail force of a number of chordwise strips on both the main and jib. Dynamic effects are modeled by using the instantaneous incident wind velocity and direction as the independent variables for the sail load contribution of each strip. The sail coefficient database was calculated numerically with potential methods and simple empirical viscous corrections. Additional aerodynamic load calculations are made to determine the parasitic contributions of the rig and hull. Validation studies compare the steady sailing hydro and aerodynamic loads, seaway induced motions, added resistance in waves, and tacking performance with trials data and other sources. Reasonable agreement is found in all cases.

Surface Water Quality Survey of Northern Indian River Lagoon from Sebastian Inlet to Mosquito Lagoon

NASA Astrophysics Data System (ADS)

Weaver, R. J.; Webb, B. M.

2012-12-01

Following news of an emerging brown tide algal bloom in the northern Indian River Lagoon (IRL), researchers sought to gain insight into the surface water quality in the IRL, as well as the extent of the algae coverage. A Portable SeaKeeper from YSI, mounted to a personal watercraft-based coastal profiling system, autonomously collected and analyzed the surface water. The system operates by recording sample data every 12 seconds while continuously underway at speeds up to and greater than 50 km/hr. The researchers covered a transect that started at Sebastian Inlet and followed a zig-zag path extending up through the Haulover Canal and into the Mosquito Lagoon. The survey path covered 166.7 km, and collected 2248 samples. Along the way stops were made at water quality stations used by the Saint John's River Water Management District, so that the data collected can be incorporated into ongoing monitoring efforts. The system analyzed the surface water for dissolved oxygen, pH, chlorophyll-a, salinity, temperature, turbidity, refined fuels, and CDOM. In the two days following the lagoon survey, the inlets at Port Canaveral and Sebastian were also surveyed for tidal currents and hydrography. The IRL transect survey data recorded evidence of the southern extent of the algae bloom in both chlorophyll-a and pH levels. Visual evidence of the bloom was striking as the water in the northern IRL turned a milk chocolaty brown color. Chlorophyll-a levels in the two inlets suggested bloom activity at these locations; however this bloom was different. This oceanic bloom was a result of a persistent upwelling event along the East Florida shelf, and the color was a paler green-yellow. The near-synoptic nature of the comprehensive lagoon survey, conducted in just over 7 hours, allows researchers to obtain a better understanding of water quality in coastal lagoons. Elevated levels of salinity, temperature, and refined fuels in the northern IRL indicate a low exchange rate and absence of flushing. Coordinated studies of circulation through the Haulover Canal, Ponce Inlet and Sebastian Inlet would aid in understanding the genesis of future bloom events.;

The New Year Wave: Generation, Propagation, Kinematics and Dynamics - Registered in a Seakeeping Basin

NASA Astrophysics Data System (ADS)

Clauss, Günther; Klein, Marco

2010-05-01

In the past years the existence of freak waves has been affirmed by observations, registrations, and severe accidents. One of the famous real world registrations is the so called 'New Year wave,' recorded in the North Sea at the Draupner jacket platform on January 1st, 1995. Since there is only a single point registration available, it is not possible to draw conclusions on the spatial development in front of and behind the point of registration, which is indispensable for a complete understanding of this phenomenon. This paper presents the temporal and spatial development of the New Year Wave generated in a model basin. To simulate the recorded New Year wave in the wave tank, an optimization approach for the experimental generation of wave sequences with predefined characteristics is used. The method is applied to generate scenarios with a single high wave superimposed to irregular seas. During the experimental optimization special emphasis is laid on the exact reproduction of the wave height, crest height, wave period, as well as the vertical and horizontal asymmetries of the New Year Wave. The fully automated optimization process is carried out in a small wave tank. At the beginning of the optimization process, the scaled real-sea measured sea state is transformed back to the position of the piston type wave generator by means of linear wave theory and by multiplication with the electrical and hydrodynamic transfer functions in the frequency domain. As a result a preliminary control signal for the wave generator is obtained. Due to nonlinear effects in the wave tank, the registration of the freak wave at the target position generated by this preliminary control signal deviates from the predefined target parameters. To improve the target wave in the tank only a short section of the control signal in time domain has to be adapted. For these temporally limited local changes in the control signal, the discrete wavelet transformation is introduced into the optimization process which samples the signal into several decomposition levels where each resulting coefficient describes the control signal in a specific time range and frequency bandwidth. To improve the control signal, the experimental optimization routine iterates until the target parameters are satisfied by applying the subplex optimization method. The resulting control signal in the small wave tank is then transferred to a large wave tank considering the electrical and hydrodynamic RAOs of the respective wave generator. The extreme sea state with the embedded New Year Wave obtained with this method is measured at different locations in the tank, in a range from 2163 m (full scale) ahead of to 1470 m behind the target position-520 registrations altogether. The focus lies on the detailed description of a possible evolution of the New Year Wave over a large area and time interval. The analysis of the registrations reveals freak waves occurring at three different positions in the wave tank and the observed freak waves are developing from a wave group of three waves, which travels with constant speed along the wave tank up to the target position. The group velocity, wave propagation, and the energy flux of this wave group are analyzed within this paper.