The 29th Student Poster Program of the OCEANS Conferences was held at OCEANS’UMTS/IEEE Kona September 19–22, 2011 at the Convention Centre at the Hilton Waikoloa Village, Kona, Hawaii. Once again outstanding work was displayed on the posters. Their work was appreciated by all who attended the conference and the student participants appreciated the opportunity to display their research work. The program was organized by Dr. Reza Ghorbani, University of Hawaii Manoa. He was assisted at the conference by Dr. Christophe Sintes, Telecom-Bretagne, France who coordinated the poster judging team. The program was supported by funding from the Office of Naval Research which enabled the students to attend the conference. Eighty six poster abstracts were received and twenty four students were invited to attend. Twenty one students were able to attend and display their posters. The posters were displayed in the Grand Promenade of the Convention Center. The students were assembled on Monday afternoon and following introductions were given instructions on displaying and attending their posters. The student award winners were announced at the Gala Luau on Wednesday evening at Kamehameha Court. Dr. Sintes opened the awards ceremony and introduced Colonel Norman D. Miller who gave a history of the Student Poster Program and then present each student with a participation certificate. The award winners were then announced and each in turn received their award from Colonel Miller. The students were introduced as a group and received a round of applause from the conference attendees. The students were announced as members of the “OCEANS Student Poster Alumni Association”.
The Students receiving awards were then announced and each came forward to receive their plaque and award. The winning students were:
Angelos Mallios – University of Girona
Janice Duty – University of Maine
Takumo Matsuda – University of Tokyo
Brendan Cahill – University of Cork
Amy Gao – MIT
Mathew Hall – University of Victoria
Following the presentation of the Student Awards the Luau continued with a wonderful evening of Hawaiian music and dance on the stage. It was a fitting end for another very successful Student Poster Program!
The students, their schools, poster titles and abstracts are listed below. The full paper of the winning paper is reprinted following this article.
Brendan Cahill, Hydraulic & Maritime Research Centre, University College Cork (Ireland), Wave Energy Resource Characterization and the Evaluation of Potential Wave Farm Sites
Abstract—In theory, the energy that could be extracted from ocean waves is in excess of any current, or future, human requirements. Methods to evaluate and compare the wave energy resource at different locations are required in order to inform the developers of Wave Energy Converter (WEC) projects and allow them to select the most favorable sites for achieving optimal power capture and economic performance from their devices as the wave energy industry begins to approach the commercial deployment of Wave Farms, arrays of full-scale WECs.
In this paper alternative techniques for the characterization of wave energy resource are presented, with particular emphasis on the identification of the practicable power available for extraction and the comparison between different potential locations for Wave Farm developments. The effect of introducing a threshold, beyond which the theoretical wave power is no longer deemed exploitable and ignored for the purposes of resource evaluation, is highlighted in order to account for the reduced device output that can be expected in severe storm conditions. In addition, the relative performance that could be expected of typical WECs located at different sites is determined using the power matrices made publicly available by the a number of device developers.
These methods are applied to measured buoy data to allow for the comparison of the wave energy resource at the Atlantic Marine Energy Test Site, a grid connected location for the testing of full scale WECs being developed near Belmullet, County Mayo, by the Sustainable Energy Authority of Ireland (SEAI), with the incident wave conditions experienced at locations on the Pacific and Atlantic Coasts of the United States. Instances where sea states with the same summary statistics display radically different spectral shapes have been identified, consequently the level of variation in the dominant spectral shapes that can exist between two ocean sites is also investigated. The effect that this spectral variation can have on the characterization of the wave energy resource at different sites and on the performance of WECs is demonstrated and discussed. It is shown that the sea states which are responsible for the largest contributions of wave power, as opposed to the most commonly occurring conditions, which should be deemed most significant for the deployment and operation of WEC installations.
Janice Duy, University of Maine (USA), Low-cost colorimeter development for the field-based detection of harmful algai blooms
Abstract—The real-time detection of harmful algal bloom (HAB)-causing organisms is crucial to preventing human illness and death, animal mortalities, and significant economic losses for coastal and fishing communities. However, most identification schemes are time-consuming and costly, which limit their use for rapid risk assessment. To address this problem, a simple colorimetric test for the HAB-causing Alexandrium fundyense/tamarense/catanella dinoflagellate species complex is presented. This work integrates an indicator dye-based bioassay for detecting toxigenic Alexandrium RNA with a custom-built two-color detector. A peptide nucleic acid (PNA) probe is used to capture target RNA, and the formation of the PNA-RNA duplex is visible as a solution color change from blue to purple with the addition of the cyanine dye 3,3’-diethyldithiacarbocyanine iodide (DiSC2(5)). PNA-RNA hybridization and discrimination against mismatched sequences is achieved within minutes at 25°C.
Hybridization signals obtained from the colorimeter are comparable to those from a benchtop spectrophotometer. The advantages of this method represent a step towards fieldcompatible, easy-to-use and inexpensive detection schemes that require minimal training for successful use.
Amy R. Gao, Massachusetts Institute of Technology, Cambridge, Massachusetts (USA), Design Considerations for Robotic Flying Fish
Abstract—This paper details an exploration into the design of an aerial-aquatic robotic vessel. A compact robot that could both swim underwater and glide in the air above water has many potential applications in ocean exploration and mapping, surveillance, and forecasting. In the first phase of this project, we focus on mechanical design concepts that would enable the biomimetic production of adequate thrust underwater. A brief review of precedent research concerning robotic fish and hydrodynamics is first presented, followed by an in-depth analysis of the mathematical theory relevant to the project. A passive model of a flying fish was constructed and launched from approximately 1 ft. underwater to determine the forces associated with overcoming drag underwater and exiting the water. Based on this, A number of conceptual designs which would produce the motion necessary for propulsion were formulated and are discussed from a mechanical design perspective. Various conventional and nonconventional actuators are reviewed, as well as a control scheme for the concepts presented. We end with a discussion of the future directions for this project, as well as the key challenges that remain to be addressed.
Rachael Hager, University of Hawaii, Manoa (USA), Geometric Optimization of a Two Dimensional Heaving Body for Power Absorption
Abstract—This project like so many has been inspired by Salter’s paper in 1974 in Nature. Salter’s Duck radiates waves only in front of the body allowing up to 80% of the incident wave’s power to be absorbed. It is its asymmetric body which allows for such high efficiency. The goal of this paper is to optimize the geometry for maximum power absorption in a two dimensional heaving body. In particular, the geometry of asymmetric bodies such as Salter’s duck will be further explored. Two numerical models are being used to evaluate the power absorption efficiency of various buoy geometries, AQWA and OcraFlex. Five of these numerical models will be confirmed via experimental work.
Mathew Hall, University of Victoria, Victoria, B.C. (Canada), The Importance of Mooring Line Model Fidelity in Floating Wind Turbine Simulations
Abstract—Accurate computer modelling is critical in achieving cost effective floating offshore wind turbine designs. In floating wind turbine simulation codes, mooring line models often employ a quasi-static approximation that neglects mooring line inertia and hydrodynamics. The loss of accuracy from using this approach has not been thoroughly quantified. To test whether this widely-used simplified mooring line modelling approach is adequate, the open-source floating wind turbine simulator FAST was modified to allow the use of an alternative, fully dynamic, mooring model based on the hydrodynamics simulator ProteusDS.
The OC3-Hywind floating wind turbine design was implemented in this newly-coupled simulator arrangement and tested using a variety of regular wave conditions. The static equivalence between the built-in quasi-static mooring model and the newly coupled dynamic mooring model is very good. Tests using both models were performed looking at scenarios of the response of the system in still water and the response to regular waves and steady winds. The dynamic mooring model significantly increased the overall platform damping in translational DOFs during motion decay tests in still water. There was very little difference between the models in coupled tests where regular wave excitation was the primary driver of platform motions, except for the addition of small levels of power in the higher frequencies of the platform motion spectrum. The nature of the different tests suggests that it is only in situations where the platform motions and wave velocities are not synchronized that the damping from the dynamic mooring model makes a large difference. This points to irregular wave conditions as providing a better test of the differences between mooring models.
Jonas Jonsson, Uppsala University, Angstrom Space Technology Centre, (Sweden), Miniaturized submersible for exploration of small aqueous environments
Abstract—Remotely operated vehicles (ROVs) are commonly used for sub-surface exploration. However, multifunctional ROVs tend to be fairly large, while preferred small and compact ROVs suffer from limited functionality. The Deeper Access, Deeper Understanding (DADU) project aims to develop a small submersible concept using miniaturization technologies to enable a high functionality. An operator is able to maneuver the vehicle with five degrees of freedom using eight small thrusters, while a set of accelerometers and gyros monitor the orientation of the submersible. A single fiber optic cable will connect the submersible to a control station and enable simultaneous data and command transfers. Rechargeable battery packs provide power to the submersibles subsystems during operation. These will be rechargeable through the fiber connection. A forward looking camera is aided by a laser topography measurement system, where distances, sizes and shapes of objects in view can be determined to within 0.5 cm. For murkier environments, or when a more extensive mapping of the surroundings is needed, the small high-frequency side-scanning sonar can be used. Salinity calculations of the water will be available through measurements of the conductivity, temperature and depth. Samples of water and particles within it will be enabled through a water sampler with an enriching capability. Flow sensors will be able to measure the water movement around the submersible’s hull. The submersible and its subsystems are under continuous development. The vehicle itself, and its subsystems as stand-alone instruments, will enable the exploration of previously unreachable submerged environments, such as the sub-glacial lakes found in Iceland and Antarctica, or other submerged small environments, such as pipe and cave systems.
Nicholas Kraus, University of Hawaii, Manoa (USA), Estimation of Wave Glider Dynamics for Precise Positioning
Abstract—The wave glider is a new autonomous surface platform with unique capabilities for persistent observation in a variety of marine environments. The applications of this novel technology continue to expand; some of the potential oceanographic applications will require precise positioning and navigation beyond the platforms current capabilities. In this article we discuss the potential for precise localization of a wave glider based on a augmenting the onboard instrumentation (adding a high quality global positioning receiver and inertial measure unit) and implementing an estimation algorithm (an extended Kalman filter using a two-body dynamic model). To understand the capabilities and limitations of the wave glider’s novel propulsion mechanism, consisting of a surface float and submerged glider to harvest wave energy for forward motion, we propose a simplified dynamic model appropriate for real-time implementation. The physical parameters of this model are identified using experimental measurements collected from a wave glider operating in a coastal environment. Finally, we present the results of a proof-of-concept field experiment where the wave glider at the surface was used to precisely position a instrument moored to the seafloor to evaluate the performance of the wave glider for the type of mission that requires precise navigation.
Angelos Mallios, University of Girona (Spain), Navigating and Mapping with the SPARUS AUV in a Natural and Unstructured Underwater Environment
Abstract—In spite of the recent advances in unmanned underwater vehicles (UUV) navigation techniques, robustly solving their localization in unstructured and unconstrained areas is still a challenging problem. In this paper, we propose a pose-based algorithm to solve the full Simultaneous Localization And Mapping (SLAM) problem for an Autonomous Underwater Vehicle (AUV), navigating in the unknown and unstructured environment. A probabilistic scan matching technique using range scans gathered from a Mechanical Scanning Imaging Sonar (MSIS) is used together with the robot dead-reckoning displacements. The raw data from the sensors are processed and fused in-line with an augmented state extended Kalman filter (EKF), that estimates and keeps the scans poses. The proposed SLAM method has been tested with a real world dataset acquired from the Spams AUV, guided in a natural underwater environment.
Tatsuya Masamura, Institute of Industrial Science, the University of Tokyo (Japan), Spectroscopy and imaging of laser induced plasmas for chemical analysis of bulk aqueous solutions at high pressures
Abstract—Laser-induced breakdown spectroscopy (LIBS) is a chemical sensing technique that has been demonstrated in numerous applications on land. This study investigates the application of LIBS as a technique for in situ analysis of the chemical composition of the ocean. The effects of pressure on the spectral emissions of various different elements in bulk aqueous solution has been evaluated, and imaging of plasmas generated in liquids at pressures between 0.1–30 MPa has been performed. The observations indicate that during the early stages of laser-induced breakdown, in the time frame when spectroscopic measurements are made, the plasma and surrounding phenomena (formation of Shockwaves and cavitation bubbles) are almost independent of the surrounding hydrostatic pressure up to 30 MPa. Spectroscopic investigations found that Na, Ca, and Mg are detectable in liquid at pressures from 0.1 to 30 MPa, at concentrations of 1, 10, and 500 ppm, respectively. These elements are of key importance in the identification of hydrothermal vent fluids. The results of this study suggest that laser induced spectroscopy is applicable for in situ elemental analysis of liquids at oceanic pressures.
Takumi Matsuda, Institute of Industrial Science, University of Tokyo, (Japan), Large area navigation method of multiple AUVS based on mutual measurements
Abstract— In this paper, we propose a large area navigation method of multiple AUVs for accurate seafloor mapping over large area. The key idea of the method is alternating roles of the AUVs between “Moving and Measuring Role (MMR)” and “Landmark Role (LR)”. AUVs in the MMR move based on the AUVs in the LR. On the other hand, AUVs in the LR keep their stations to act as landmarks for the moving AUVs. By alternating their roles, the two groups of AUVs can observe a large area.
AUV position is estimated by mutual measurements of distance and direction among them. These measurements are fused with other on-board sensors such as DVL, angular rate gyro and depth sensor by particle filter, a probabilistic state estimator, in order to realize stable positioning robust against sensor noises and lack of measurements.
We verified the performance of the method through simulation based on data obtained during various experiments performed in pool and at sea. Through the simulation, we demonstrated that the proposed method achieves a positioning error considerably smaller than dead reckoning and thus a stable navigation over an area larger than achieved by a single AUV.
Lashika Medagoda, Australian Centre for Field Robotics, University of Sydney (Australia), Water Column Current Aided Localisation for Significant Horizontal Trajectories with Autonomous Underwater Vehicles
Abstract—Survey class Autonomous Underwater Vehicles (AUVs) rely on Doppler Velocity Logs (DVL) for precise navigation near the seafloor. In cases where the seafloor depth is greater than the DVL bottom lock range, localising between the surface, where GPS is available, and the seafloor presents a localization problem since both GPS and DVL are unavailable in the mid-water column. Previous work proposes a solution to navigation in the mid-water column that exploits the fact that current profiles of water columns are stable over time. With reobservation of these currents with the ADCP (Acoustic Doppler Current Profiler) mode of the DVL during descent, along with sensor fusion of other low cost sensors, position error growth can be constrained to near the initial velocity uncertainty of the vehicle at the sea surface during the dive, and following DVL bottom lock, the entire velocity history is constrained to an error similar to the DVL velocity uncertainty, and coupled with a tactical grade IMU, 12m (2) per hour position error growth is possible. Application on real data coupled with view-based SLAM, without the use of an IMU, has also been demonstrated on the Sirius AUV. The limitation of this method is that it does not accommodate significant horizontal transit such that the water current velocity within the horizontal layer changes spatially, instead focusing on vertical motion through the water column. This paper addresses this limitation by extending the method through a number of modifications, with the result allowing accurate localization during significant horizontal transits. Preliminary results from the Sirius AUV are outlined showing the applicability of this method.
Ruth L. Mullins-Perry, Texas A&M University, College Station, Texas (USA), Interdisciplinary Ocean Observing Applications for Investigation Coastal Hypoxia in the Gulf of Mexico
Abstract—Despite advances in ocean observing technologies, operational difficulties and constraints with surveying in coastal waters still remain. Coastal observing awareness has increased recently with the Gulf of Mexico (GOM) Deepwater Horizon oil spill, hurricanes, and persistent environmental hazards, such as harmful algal blooms and hypoxia. To overcome limitations in coastal sampling, we implemented an interdisciplinary approach by integrating traditional ocean observing platforms with advanced shipboard instrumentation and high-resolution numerical models. This integrative effort improves the monitoring and prediction of coastal hypoxia in the GOM. This publication provides an overview our effort by presenting historical, survey, and model observations specific to investigating hypoxia on the TX shelf. The discussion will highlight future directions for integrating and analyzing these data sources and emphasize how coastal integration of these resources can significantly improve coastal hazard science in the GOM.
Geol-Ju Kim, Gangneung-Wonju National University (South Korea), A micro wireless remotely-operated vehicle
Abstract—For decades remotely-operated vehicles (ROVs) have been designed and implemented in various size and shape. Among them, very small-sized ROV which is called micro ROV has the working range with tens of meters and takes the place of divers. In this paper, we develop a micro ROV operating not by umbilical cable which is troublesome for movements but by wireless acoustic communication. The micro wireless ROV is designed to conduct the commands of movement and measurement from a remote user and to report the result. Experiments in water tanks have verified functional operations of the vehicle and shown the feasibility for applications.
Eric C. Piper, Florida State University (USA), Oil Droplet Transport in the Gulf of Mexico
Abstract—The Deepwater Horizon oil spill released 5 million barrels of oil deep in the Gulf of Mexico. The high pressures and turbulent flow at the wellhead resulted in shearing forces that created oil droplets of generally microscopic size. Although initially buoyed upward due to initial velocity and natural gas bubbles entrained in the flow, these oil droplets were eventually transported according to Stokes’ Law and ocean currents.
Qun-yan Ren, Universite libre de Bruxelles (Belgium), A robust passive interferometry technique for sediment geoacoustic characterization
Abstract—Due to the dispersive characteristics of acoustic propagation in shallow water, the broad-band sound field excited by a passing ship usually exhibits an interference structure with the form of striations in the space-frequency plane. Waveguide invariant theory is derived to interpret the striation slope and has been used for underwater inverse problems including sediment geoacoustic characterization, source localization, target recognition and others. Owing to the interference structure processing methods previously used, most applications only use the overall striation slope as acoustic observable, however, the local striation structure that is also closely related to the environmental properties was not considered. In this paper, a passive acoustic interferometry technique is proposed for sediment geoacoustic characterization using local striation features extracted by a multi-scale line filter. Based on the Yellow Shark environmental model, a synthetic study using the proposed method is presented for sediment geoacoustic characterization. The robustness of the passive acoustic interferometry technique to source depth and range uncertainties are also studied by theory analysis and numerical simulation. Finally, the acoustic data due to passing ships collected in Mediterranean Sea in 2007 are processed to test the feasibility of the proposed method.
Catalin David, Jacobs University, Bremen (Germany), Energy Consumption Analysis of Underwater Acoustic Sensor Networks
Abstract—Energy-efficiency in underwater networks is essential since nodes are mostly battery powered and it is difficult to replenish their supply. Furthermore, since underwater acoustic sensor networks are effected by ambient environmental conditions leading to volatile network dynamics, large propagation delays and a high probability of error in transmissions, it is even more important to analyze the energy consumption characteristics in order to build an energy efficient robust network. Since the underwater acoustic channel behaves differently in deep water and shallow water it is important to understand the energy consumption characteristics of both channels. In this paper we present an overview of a study conducted to analyze the energy consumption in underwater acoustic sensor networks. The energy consumption for different transmission mechanisms (single-hop, multi-hop, etc.) are analyzed not only in deep and shallow water channels but the effect of varying ambient conditions are also presented.
M. Jordan Stanway, Massachussets Institute of Technology/Woods Hole Oceanographic Institute, Massachusetts (USA), Dead Reckoning Through the Water Column with and Acoustic Doppler Current Profiler: Field Experiences
Abstract—Underwater vehicles currently rely on external acoustic tracking systems to estimate position when away from the surface or the seafloor. Many vehicles dead reckon near the seafloor using a Doppler velocity log. This paper presents a method for dead reckoning through the water column using overlapping water profiles measured by a vehicle-mounted acoustic Doppler current profiler. Under mild assumptions, the vehicle can simultaneously estimate its own global velocity at the same time as identifying the ocean current profile. The estimation problem is solved using batch least squares, recursive least squares, or a simple online depth bin averaging scheme. We discuss challenges encountered in implementing the approach during three field deployments of the autonomous underwater vehicle Sentry, and provide estimates of the ocean current, the vehicle velocity, and integrated position.
Navid Tahvildari, Texas A&M University, College Station, Texas (USA), Generation of oblique interfacial waves due to resonant interaction with surface gravity waves in shallow water
Abstract—Ocean in deep waters and coastal areas is stratified due to vertical gradient of density. Due to nearly distinct interface between the layers of constant density, a two-layer system is a commonly used configuration to model ocean waters. In such models, various mechanisms can lead to generation of surface and interfacial waves. Furthermore, this system admits nonlinear interactions between surface waves and internal waves. As surface waves approach coastal areas, they become long relative to water depth and through nonlinear interactions can induce long interfacial waves over fluidized seabed. This phenomenon will be studied theoretically in the present paper. The fluid is composed of two layers of density stratified, incompressible, inviscid and immiscible fluids. The depth of the top and bottom layers are assumed to be shallow relative to the typical surface wave and interfacial wave length respectively. The waves in this system are weakly nonlinear and weakly dispersive and can be described by Boussinesq-type equations. First, Boussinesq-type equations describing the displacements of the surface and interface and the depth-integrated horizontal velocities in the two layers are derived for mildly varying bathymetry. Secondly, the nonlinear resonant interactions among surface and interfacial modes are analyzed via a second order multiple scales analysis in time. Consequently, coupled transient evolution equations of wave amplitudes are derived. The results of inviscid theory indicates generation of a pair of oblique subharmonic interfacial waves due to energy gain from surface wave. In a parametric study, the influences of the angle of propagation of interfacial waves with respect to surface wave, lower layer viscosity, surface wave frequency, density difference between fluid layers, thickness of the fluid layers, and surface wave amplitude are studied.
Alexei Winter, University of Bristol (UK), A constrained optimization process for the design of tidal turbine blades with experimental validation
Abstract—This paper presents a way of conceptualizing the design of rotor blades for tidal turbines. The method uses systems principles and attempts to highlight the need to design the rotor within the context of other system components, rather than pursuing the goal of optimizing design point performance in isolation. The method begins by assuming that the axial induction factor is a primary design variable rather than it being fixed at a value of 1⁄3. Example geometries are presented from this method, as are their performance characteristics. It is shown that blades designed in this way can exhibit thrust characteristics that are significantly different from a rotor designed to operate at an induction factor of 1⁄3 (one example shows a 68% decrease in runaway thrust). Furthermore, experimental work was undertaken designed to confirm these differences in performance characteristics. Results show very good correlation with predictions.
Ashley Lloyd, Franklin Olin College of Engineering, Massachussets (USA), Busting the Myth: The Corrosion Resistance of Cast vs. Forged Aluminum for use in Ocean Engineering
Abstract— The pitting and intergranular corrosion of cast aluminum alloy A3 56 were compared to that of aluminum alloy 6061 to test whether cast aluminum alloys can be used as a substitute for 6061 in select ocean engineering applications. Accelerated corrosion tests were conducted in a salt water and hydrogen peroxide environment at elevated temperature for over six hours. Metallographic samples were then examined for evidence of corrosion. While both aluminum samples showed some evidence of corrosion, there was no substantial difference between the corrosion of the two samples. We conclude that the viable use of certain heat-treatable cast aluminum alloys in a seawater environment has been experimentally verified.
Bradley Keogh, University of Southampton (UK), Experimental investigation of inter-array wake properties in early tidal turbine arrays
Abstract—Full-scale marine current energy converter devices have now been operational for several years. These devices have the potential to provide large scale electricity generation when placed in farms/arrays in areas of fast flowing tidal currents. Now the full-scale concept has been proven experienced operators are in a position to provide array developers with devices for such applications, thus at present the first tidal arrays are in the planning and consenting stage around the globe. The inter-device spacing within these arrays can have a profound effect both on the flow field through the array itself and the on the surrounding environment. This paper describes a set of scale experiments aimed at investigating the interaction of devices within an array and potentially highlight some of the pitfalls of future array design which may result in sub-optimal device operation. Experimental results presented herein indicate that particular spacing can lead to regions of accelerated flow which may be exploited to provide greater power production. Further examination of this accelerated flow region is presented, with discourse surrounding the potential issues of placing devices in this region, and impacts the on array geometries as a whole are discussed.