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Table 1

Open Ocean Aquaculture Engineering

OOA Progress Report for the period 1/01/01 through 12/31/01

Principal Investigator(s): Ken Baldwin, Barbaros Celikkol, Pedro de Abla, Judson DeCew, Oleg Eroshkin, David W. Fredriksson, Glen Rice, Rob Swift, Igor Tsukrov, UNH; James D. Irish, Walter Paul, Woods Hole Oceanographic Institution

Accomplishments
Scheduled Tasks:
Overview
The University of New Hampshire, Center for Ocean Engineering (UNH/COE) component of the Open Ocean Aquaculture (OOA) project continues to be focused on developing engineering analysis and design tools. These tools are used for evaluating and optimizing engineering systems required for successful open ocean aquaculture. This overall focus was employed and enhanced in the recent funding period activities. The individual tasks are:

  1. Monitoring, Modeling, Engineering Analysis
    The existing open ocean demonstration site with the Ocean Spar cages and submerged grid mooring system was instrumented in a collaborative effort with the Woods Hole Oceanographic Institution (WHOI) to monitor the cage excitation and response. The resulting motion and load data sets were compared with physical model and computational model results to refine the modeling techniques and improve the understanding of the dynamics of the cages and mooring systems load and motion response.
  2. Optimal System Design
    Alternative cage and mooring systems were also investigated. The effort began with the numerical modeling of the REFA 2200M tension leg (REFA) cage/mooring system, described in the FY2000 OOA progress report. The REFA numerical model results were promising, but the physical model revealed problems with the surface floats, which were later verified in a visit to a REFA cage site. Another cage system being evaluated is the Russian fabricated SADCO-Shelf system, which commenced in the autumn of 2001.
  3. Anchor Designs
    Optimization continued with studies of novel anchoring techniques to reduce the area required for a mooring system. A number of alternatives were considered: gravity anchors, helical anchors, water jet/self embedding anchors, and a "floatable" anchor. The latter concept received the most attention. This concept was basically a gravity anchor with ballast control.
  4. Feed Systems
    A critical issue for overall fish production optimization is remote automated feeding. Two approaches were investigated. The MIT Robo-feeder was deployed on top the Spar after major alterations in the system were performed at the Chase Ocean Engineering Laboratory at UNH. An independent feed buoy with a feed hose to the cage was also deployed. The feed hose was developed at WHOI.
  5. Mussel Long Line Modeling
    Numerical modeling of mussel lines was commenced. These studies provided insight into the dynamics of these lines in the open ocean.

Important Results or Findings

  1. Monitoring, Modeling, Engineering Analysis A significant portion of this year's effort focused upon the understanding of fish cage and mooring system dynamics to wave and current forcing. This approach includes:
    1. Monitoring mooring and cage dynamics
    2. Physical modeling motion and load response.
    3. Numerical modeling motion and load response.
    4. Comparative analysis.
The work was performed collaboratively between the University of New Hampshire and the Woods Hole Oceanographic Institution.

Woods Hole Oceanographic Institution Component
The Woods Hole Oceanographic Institution (WHOI) is working with the University of New Hampshire at their Open Ocean Aquaculture demonstration site to (1) instrument a fish cage mooring with load cells to measure the tension in the mooring lines, (2) measure the wave forcing on the fish cage mooring and fish cage, and (3) instrument the fish cage itself with a motion package to monitor its response to wave forcing. In the first year (2000) of this effort the equipment was constructed and tested at WHOI. In the second year (2001) it was deployed in a joint effort with UNH. The instrumentation and preliminary results are described in a WHOI Technical Report (Irish et al, 2001b). Mooring Line Tension. Measuring the tension in the fish cage mooring lines required placing load cells in 9 locations (Irish et al, 2001a). The load cells have capacity comparable to the mooring components (approximately 20,000 lbf). They were designed to mount on an in-line bar enabling them to be shackled into the mooring system. The design also accounted for any potential damage to the cables, which could cause fatigue failures. The system was constructed so that the recorder could be removed easily by divers for servicing (Figure 1).

The load cell recorders were constructed around a Persistor CF1 microprocessor with 12 bit 8 channel A/D, internal clock, low power circuitry, and compact flash data storage media. They were designed to meet the requirement of 120 days between servicing. The systems run PicoDOS and used the Code Warrior C/C++ development system to develop the software. The instruments record every three hours for 20-minutes, sampling at 10 Hz. The pressure cases were constructed of PVC with titanium hardware for low corrosion and weight.

The load cells were deployed during the week of 21-25 September 2000 when the mooring and fish cage were deployed (Irish, et al., 2001a), and the recorders attached on 23 October 2001. Instrument deployment details are provided on Table 1.

Load cells and recorders were placed at the top of each of the four anchor lines in the mooring of the north cage. Because severe weather in the region comes from the Northeast, that mooring leg was heavily instrumented with a load cell in each of the four lines attaching to the grid ring at the float. To accommodate the four load cells at the northeast grid corner, one recorder in the lower riser line to the fish cage logged data from all four load cells. A cable assembly attached the four load cells to one underwater pluggable connector in the recorder.

Wave Forcing of the fish cage and mooring. To measure the wave forcing on the fish cage and mooring, a wave rider buoy was constructed and deployed (Figure 2). The instrument includes a 3-axis accelerometer that measures the motion of the buoy as it follows the waves. The acceleration is recorded and later integrated to obtain vertical displacement (wave amplitude). The buoy is moored with a compliant elastic element to allow it to move freely in the waves, yet remain in position to the east of the northern fish cage. The wave rider buoy was deployed 4 January 2001 and recovered 15 March 2001 (Table 1).

The Persistor recorder was also used in the wave rider, but with a spread spectrum telemetry link. The accelerometer has low-pass filters to prevent aliasing with a 10 Hz sampled bursts for 20 minutes every three hours to be compatible with the load cell recorders and fish cage motion package. The three-hour interval between bursts was selected to allow the wave field to become de-correlated. The wave rider electronics powers up the accelerometer on the hour every three hours. The data were digitized and recorded internally on compact flash media, then GPS data (for time and position) were temporarily recorded and the system shifted to "lower power" mode. At 48 minutes after the hour that the system recorded the data, it powers up the Datalinc spread spectrum radio and telemeters the last record to shore. Problems with the radio link resulted in reduced data recovery for real time analysis, but all data sets were internally recorded and recovered.

Fish Cage Motion. The response of the fish cage to the wave forcing was measured with a motion package built around a Systron Donner 6-axis motion sensor measuring 3 axes of acceleration and 3 axes of rotation (Figure 3). A recording and control system was constructed using a PC-104 computer running DOS with a 6 GB hard drive for data storage. A 16 channel 12 bit A/D digitizes the six channels of Motion Pak data. This system has the capability of switching battery power to various sensors and providing regulated power to the Motion Pak. Included are low-pass anti-aliasing filters between the Motion Pak and the A/D. A clock board removes power from the whole system between bursts so that total system power is conserved. The clock powers up the system at the programmed time, executes the sampling software, resets the wakeup clock and goes back to "sleep." Sampling is compatible with the wave rider and load cell systems and the data sets are stored to hard disk.

The motion package system was transported to UNH just after Christmas 2000 and deployed on 18 January 2001. On 9 February, divers recovered it from the fish cage, the system was checked, the data downloaded and examined. As the disk drive had plenty of storage space, the data was left on the disk as a backup. A new battery was installed, the system checked and redeployed (Table 1). After the large 6-7 March 2001 storm, the motion package was recovered and the data examined. During this storm, the counter weight broke off the fish cage, and it was riding at the surface for about a month until a new counter weight was obtained and attached. After recovery the data system was checked for calibration of the A/D, and then the data sets were normalized using the factory calibrations.

Summary. Data from the load cells (mooring tensions), wave rider (wave forcing) and motion package (fish cage response) were collected. The preliminary results show (1) reasonable mooring tensions with fluctuations due to tides and storms, (2) significant wave forcing that is consistent with National Data Buoy Center weather buoy (Boston and Portland) observations, and (3) fish cage motions that are consistent with previous computer and physical modeling efforts. After recovery, the data systems and sensor calibrations were checked and a database assembled. The final processing of these data and write up of the results is continuing in 2002 in a joint WHOI-UNH effort. Of critical importance is the response of the fish cage which will be obtained from the detailed wave and motion package bursts which will provide the response of the fish cage in heave, roll, tilt and angle movement about the three axes.

University of New Hampshire Component
The focus of the UNH component of the "Monitoring, Modeling and Engineering Analysis" part of the project includes analyzing the field data collected from the WHOI designed instrumentation for a comparative analysis between physical and numerical modeling techniques.

Physical Modeling. Physical model tests were conducted in the UNH/COE tow/wave basin (Figure 4) using a Froude-scaled representation of the northern deployed fish cage and mooring system. The tests were performed using both regular and random wave conditions. Fish cage motion response in heave, surge and pitch were measured and frequency dependant linear transfer functions calculated. Mooring line tension was also measured at the anchor and bridle lines and transfer functions calculated using auto- and cross-spectral techniques. Analysis was performed in the frequency domain to examine the system dynamics and for comparison with numerical and in-situ data sets. In addition, resonant conditions were investigated so the use of the configuration currently deployed is optimized. The results from these tests are discussed below in a comparative analysis of the in-situ field observations, physical and numerical modeling.

Numerical Modeling. A series of numerical modeling tests were also conducted in the effort to validate existing techniques to better approximate fish cage and mooring system dynamics currently deployed at the demonstration site. Improvements to the numerical model described by Ozbay (1999) and Tsukrov et al. (2000) to better simulate system dynamics include incorporating a bottom conditional to model component and ocean floor interaction and random waves to provide more realistic forcing (see FY2000 report). The primary goal in the validation process was to perform regular and random wave simulations identical to those performed as part of the physical modeling efforts. Linear transfer functions using auto- and cross- spectral analysis techniques were used to calculate a set of normalized parameters to compare with the results of the physical model tests and in-situ field observations. Figure 5 shows the numerical model of the deployed fish cage in the static position.

Comparative Analysis. To compare the results from the physical and numerical model tests to the field observations, transfer functions were calculated (Fredriksson, 2001). For the regular wave tests, response amplitude operators for heave, surge and pitch motion response and for the anchor and bridle line loads were calculated for ten wave frequencies. These values were compared to the frequency domain linear transfer functions obtained from the random wave tests. Auto- and cross-spectral density calculations for the physical and numerical model simulations were performed. Transfer functions were also calculated using the in-situ data collected. Data sets from northeast storms were downloaded from the wave rider buoy, anchor and bridle line load cells and the cage accelerometers. The normalized transfer functions were then compared to those calculated using the physical and numerical modeling methods.

The motion response comparison between the physical and numerical model results matched remarkably well. Motion response data in heave and surge indicated a damped system in this degree of freedom. In pitch, however, a resonant condition was identified due to the swinging motion of the pendent weight, which failed during one of the winter storms. The transfer functions for the anchor and bridle line loads also showed agreement. These values can be used to predict mooring loads for various design waves. For a detailed discussion regarding these data sets and results, see Fredriksson (2001).

Gulf of Maine Survival. Another significant result of this investigation is that both the northern and southern cage mooring systems survived two Gulf of Maine winters. In the first winter, each of the central spar cages was placed in the submerged configuration. In the second winter, the cage of the refurbished northern system was kept at the surface to collect motion response and mooring line tension engineering data. Both the cage and the mooring survived multiple northeast storms. Furthermore, during the most severe storm occurring on March 6, the maximum Hmo was calculated to be 8.27 meters with peak periods over 11 seconds. This engineering test showed that the design concept and safety factors developed in the initial stages of the project were not only sufficient but also robust. This design philosophy is necessary in a demonstration project to ensure research continuity. Once the concept is proven, steps can be taken not only to test candidate species and ancillary equipment (i.e. feeding systems) but also to evaluate and optimize the engineering methods necessary to build an economical open ocean aquaculture facility.

  • Optimal System Design
    Evaluation Tools - Net Modeling. As part of the "Optimal System Design" portion of the project, design tools are continuously being improved so design and analyses become more accurate. One such improvement was the addition of a consistent finite element. This element was developed to model the hydrodynamic response of net panels to environmental loading. This consistent net element is constructed to reproduce the drag, buoyancy, inertial and elastic forces exerted on the netting by current and waves (Tsukrov et al., 2002). It was implemented in the finite element program Aqua-FE used in the UNH/COE to analyze the dynamic performance of various structures subjected to mechanical and current/wave-related environmental loading.

    To evaluate the accuracy of the proposed finite element modeling, numerical predictions were compared with the experimental observations and (simplified) analytical results of other researchers. Using this technique, models of a 1m x 1m net panel with 4, 24 and 544 elements were created and subjected to variable velocity input. The results were compared with semi-empirical formulae of Kawakami (1964) and Aarsnes et al. (1990). Note: the full cited references for Kawakami and Aarsnes can be obtain from Tsukrov et al. (2002). The comparison shows that our simulations predict lower drag forces (Figures 6, 7). The reason for this is that our model accounts for deformation of the net panel reflecting the fact that drag forces on net strands partially cancel each other. We also use the drag coefficients that depend on Reynolds number, while formulae of Kawakami (1964) and Aarsnes et al. (1990) have drag coefficients dependent upon geometrical parameters only.

    The proposed approach to net modeling was applied to the analysis of a tension leg fish cage REFA considered for deployment at the UNH open ocean aquaculture demonstration site. The finite element model of the REFA cage is shown in Figure 8. Various environmental loading conditions were considered. The results were compared with the predictions obtained using the equivalent truss elements to model nets (Tsukrov et al., 2000) as shown in Figures 9 and 10. It was shown that the latter approach overestimates the stresses in the fish cage because it over predicts the inertia of the system. The finite element simulations also show that 21 special (consistent) net elements per net panel are enough to adequately represent the influence of the net on the overall dynamic characteristics of the considered fish cage system.

    REFA Cage Physical Modeling Investigation. Preliminary numerical model tests suggested that the REFA cage system could be a candidate for deployment at the demonstration site (see FY2000 report). To further investigate the system, a series of physical model tests were conducted to assess the wave response characteristics of a cage in the UNH wave tank. Since the entire cage/mooring system dynamics was of interest, the scale ratio was based on the ratio of tank depth to site depth yielding a model to full scale ratio of 1/21.3. The resulting model, shown in Figure 11, was approximately 0.8 meters tall and 0.8 meters in diameter. Dimensions and weights were scaled directly from the manufacturer's literature, and the model netting maintained the same "solidity" (percent twine projected area to total net panel area) as netting specified by the manufacturer. To exactly duplicate the mooring system geometry, the six vertical anchor chains were attached at the bottom to a single, large, heavily ballasted base plate. Anchor chain length was adjusted so that there was slack in the "throat" - the netting between the upper flotation buoys and the floating collar where net pen diameter is reduced. The purpose of including this flexibility was to accommodate tidal changes in water level.

    The model cage was placed in the wave tank opposite side observation windows so that the cage response to a series of single frequency waves could be characterized. Following standard naval architecture practice with respect to seakeeping tests, Froude scaling was used to convert model scale wave parameters to equivalent full scale values. Periods ranged from 2.3 to 13.8 seconds (full scale) and maximum wave height was 5.5 meters (full scale).

    At low frequencies (full scale periods of 6.9, 9.2, 13.8 seconds), the lower and upper buoy planes moved horizontally in time with the wave motion. The tension leg configuration effectively prevented vertical motion of the main cage body. The floating collar contoured the wave surface with the throat acting as a flexible diaphragm. The floating collar just began to dip the down-wave side of its rim at a wave height of 5.5 meters (full scale). Vertical motion of the cage bottom netting was also perceptible but did not significantly reduce the interior volume.

    At higher frequencies (full scale periods of 4.6, 3.5 and 2.3 seconds), horizontal movement of the buoy planes and the main body of the pen was reduced. At full scale periods of 3.5 and 2.3 seconds, the main body of the cage was almost motionless due to system inertia. For the most part, the floating collar followed the wave surface with the throat acting as a diaphragm. The highest frequency waves, however, contained some intermittent wave chop, and this occasionally caused splash-over.

    Overall, the main body of the cage, between the lower and upper buoy planes, maintained a stable volume. Horizontal motion (only) appeared in response to long period wave forcing. For short period excitation, the main volume was nearly stationary. The throat netting above the upper flotation buoys was highly energetic as the floating collar moved vertically with the wave surface. Observations indicated that chafe would be of major concern.

    SADCO-Shelf cage investigation. Another cage system being considered for future deployment is the Russian fabricated SADCO-Shelf submersible system (Figures 12 and 13). To begin the computer and physical model evaluation process, Dr. Leonid Buogrov of SADCO-Shelf Ltd from St. Petersburg, Russia visited UNH to introduce and provide specifications for their submersible fish cage. The information given to UNH/COE will be used to perform a numerical and physical analysis of the cage under the Gulf of Maine's environmental conditions. The UNH numerical model Aqua-FE will be utilized as well as physical modeling in the UNH/COE research tanks. Using these tools, the cage will be subjected to sinusoidal and random waves while at the surface and submerged. Once the analysis is complete, a recommendation will be made about the cage and its ability to withstand the loading conditions at the site.

  • Anchor Designs
    Ballasting anchor. Another Task in the engineering component of the OOA demonstration project is the research of novel anchor designs. One such system being investigated is a deadweight anchor that can be retrieved by displacing water chambers with air. This component of the project addresses the basic problem to develop a deadweight fish cage anchor which will be low-cost, deployable in up to 200 ft of water and recoverable for periodic maintenance of attachments to the cage. The basic concept is that of a concrete ring with a central concrete stiffening rib, with cover plates top and bottom. Testing concentrated on a reduced-size prototype 4ft 11 in. in diameter and 17 in. high. The concrete ring and stiffening rib are 4.5 in. thick, and are covered with 0.25 in-thick steel plates, bolted to the concrete structure. A central attachment eye is cast into the stiffening rib. The anchor weighs 1585 lb in air and 940 lb in water.

    The recovery procedure consists of injecting compressed air into the anchor in such a way that water is expelled from one side first, so that the anchor rises with its diameter practically vertical, and rights itself as it approaches the surface. This was found to be a much more reliable procedure than attempting to raise the anchor horizontally. This behavior was checked in repeated tests in the 6-m (20-ft)-deep pool in the Chase OE Laboratory.

    Field testing was then carried out in Portsmouth Harbor, from the RV Gulf Challenger in a depth of approximately 15 m (50 ft) of water. To launch the anchor, an air bag was attached to the central lifting eye by a line about 2 m shorter than the depth of the water. The anchor was then flooded, which caused it to swing down under the bag, effectively slowing the anchor down to avoid a violent impact with the bottom. The bag was then partially deflated to allow the anchor to sink to the bottom. The anchor was then recovered by injecting compressed air as in the pool tests. The launching and recovery systems worked very well.

    The field and pool tests show that the basic design is feasible, and that the prototype can be both launched and recovered effectively. Most recently, testing has concentrated on replacing the steel cover plates with less expensive materials. A top cover of 40-mil PVC geofabric has been found to satisfactorily replace the top steel plate in pool tests. Based on these results, we are proposing a design for the full-scale anchor with an integral concrete bottom and sides and a geofabric cover. Dimensions will be decided on once the final cage configuration is chosen.

  • Feed Systems
    Floating Feed system. Feeding systems are also being developed and deployed at the demonstration site as part of the open ocean aquaculture engineering project. Over the last year a feed system, including a buoy, feed hopper, timer, feed delivery system and buoy mooring, have been designed, built and deployed (Rice et al., 2001). UNH/COE designed the buoy to hold approximately 225 kg of feed above the water line to avoid the need for pressurization of the feed hopper or specialized valves and locks to keep the stored feed from getting wet and spoiling. The feed is metered from the hopper at timed intervals and mixed with water to be flushed out the bottom of the buoy. Construction of the buoy shell took place at Stommel Fisheries in Woods Hole, MA. The internal components were added and tested at UNH, and dynamic pool testing of the buoy took place at the UNH Chase Ocean Engineering test tank. Mooring design was jointly done between Buoy Technologies in Concord, NH, and using the UNH Aqua-FE numerical model (Figure 14). The mooring system is three legged and comprised rubber bands and rope, attaching to the existing grid system used by the fish cages. Feed is delivered through a stretchable hose from the Woods Hole Oceanographic Institution. A sinking feed falls out the bottom of the buoy and travels through the hose to the cage, while the stretchy nature of the hose allows for free motion of the buoy in storm conditions. A sunset picture of the deployed feed buoy is shown on Figure 15.

    Robofeeder Modifications. The Robofeeder was delivered to the UNH/COE in August of 2001. From August to October, the feeder's systems were strengthened to be able to endure the harsh New England winters. The pneumatic system was overhauled, changing all air hoses, connections and hardware. Waterproofing measures were taken to the feeder housing and electronics' box. The location of the gate valve for the feed was to low for the feed to be able to pour into the cage. The top of the spar was modified and a pump added to the system to flush the feed through the hosing and avoid any feed jams. During the refurbishing phase of the feeder, an analytical and physical analysis was performed to determine the effects of the feeder on top of the cage. The cage was found to lose 42 % of its righting moment and would have a lean of 5 - 10 degrees depending upon how much feed was loaded. But the righting moment was still acceptable and the system was deployed in November of 2001 (see the Management/Operations progress report).

  • Mussel Long-Line Modeling
    Another Task and area of research recently conducted involved the numerical modeling of the UNH mussel long-lines deployed at the demonstration site. During the months of February and March of 2001, a numerical analysis of a simplified mussel line was completed using Aqua-FE. The system response to sinusoidal and random seas, as well as varying current conditions was investigated. Six different scenarios with two models were tested to observe the system's displacement response: the first three simulated a constant current, but varying wave heights and lengths and the second three scenarios had a constant wave height and length, but the current was modified.

    The second section of this research was to verify the Aqua-FE results by comparing the drag force acting on one component of the system. The drag force projected by a computer simulation of a line of set properties was compared to the analytical solution of force acting on the same body. The results were compared and determined that the Aqua-FE results were accurate within 6%. Figures 16 and 17 shows one time step of the numerical model simulation with and without mussel socks attached to the long-line.

    Difficulties Encountered
    Results and/or findings are provided in each section describing the progress of the individual tasks.

    Anticipated Success in Meeting Project Objectives in Scheduled Project Period
    Significant headway was made in the completion of the net cage system through the incorporation of Feed Buoy Systems for both the surface cage and the subsurface cage of the OOA program. The instrumentation of the net cage and its mooring system, and the deployment of a wave rider buoy have enabled the program to record all pertinent engineering and site environmental data. The gathered data have greatly improved the understanding of the net cages and their mooring, and the complex interaction of the cage systems with the sea state, wind, and ocean current environment. The progress in numerical and physical modeling is benefiting the soundness and optimization of the engineering design of the deployed cages and the submerged mussel longline. The project also contributes to the educational goals of the University of New Hampshire, and strengthens the quality and status of the Open Ocean Aquaculture (OOA) program.

    Reports, Manuscripts, and Presentations Resulting from the Project

    Journal Publications
    Baldwin, K., B. Celikkol, R. Steen, D. Michelin, E. Muller, P. Lavoie (2000). Open Aquaculture Engineering: Mooring and Net Pen Deployment. Mar. Tech. Soc. J. Washington D.C. Vol 34, No. 1 pp 53-67.

    Fredriksson, D.W., M.R. Swift, E. Muller, K. Baldwin and B. Celikkol (2000). Open Ocean Aquaculture Engineering: System Design and Physical Modeling. Mar. Tech. Soc. J. Washington D.C. Vol 34, No. 1, pp. 41-52.

    Tsukrov, I., O. Eroshkin, D. Fredriksson, M.R. Swift and B. Celikkol. (2002). Finite Element Modeling of Net Panels Using Consistent Net Element. Accepted for publication to Ocean Engineering.

    Tsukrov, I., M. Ozbay, D.W. Fredriksson, M.R. Swift, K. Baldwin, B. Celikkol (2000). Open Ocean Aquaculture Engineering: Numerical Modeling. Mar. Tech. Soc. J. Washington D.C. Vol 34, No. 1 pp 29-40.

    Conference Publications/Presentations
    Fredriksson, D.W., M.R. Swift, J.D. Irish and B. Celikkol. (2002). The Heave Response of a Central Spar Fish Cage - OMAE2002-28441, Proceedings of the 21st International Conference on Offshore Mechanics and Arctic Engineering. Oslo, Norway (In preparation).

    Fredriksson, D.W., E. Muller, M.R. Swift, I. Tsukrov and B. Celikkol (1999a). Offshore Grid Mooring/Net Pen System: Design and Physical Model Testing. OMAE99-3064. In: Offshore Mechanics and Arctic Engineering '99. Proceedings of the 18th International Conference. St. JohnÕs, Newfoundland Canada: ASME.

    Fredriksson, D.W., E. Muller, M.R. Swift and B. Celikkol (1999b). Physical Model Tests of a Gravity-Type Fish Cage with a Single Point, High Tension Mooring. OMAE99-3066, In: Offshore Mechanics and Arctic Engineering Õ99. Proceedings of the 18th International Conference. St. JohnÕs, Newfoundland Canada: ASME.

    Fredriksson, D.W., M.J. Palczynski, M.R. Swift and J.D. Irish. (2001). Fluid Dynamic Drag of a Central Spar Cage Open Ocean Aquaculture IV, June 17-20, St. Andrews, NB, Canada, Mississippi-Alabama Sea Grant Consortium, Ocean Springs, MS. MASGP-01-006, 2001 (submitted).

    Gosz, M., K. Kestler, M.R. Swift and B. Celikkol (1996). Finite Element Modeling of Submerged Aquaculture Net-pen Systems. In: Open Ocean Aquaculture. Proceedings of an International Conference. May 8 - 10, 1996, Portland, Maine, Marie Polk, Editor. New Hampshire/Maine Sea Grant College Program Rpt. #UNHMP-CP-SG-96-9. pp. 523-554.

    Rice, G.A. M. Stommel, M.D. Chambers and O. Eroshkin, (2001). The Design, Construction and Testing of the UNH Feed Buoy. Open Ocean Aquaculture IV, June 17-20, St. Andrews, NB, Canada, Mississippi-Alabama Sea Grant Consortium, Ocean Springs, MS. MASGP-01-006, 2001 (submitted).

    Savage, G.H., W.H. Howell, R. Barnaby, and B. Celikkol (1997). Demonstration of Open-Ocean Aquaculture of Groundfish. In: Open Ocean Aquaculture '97, Charting the Future of Ocean Farming. Proceedings of an International Conference. April 23-25, 1997, Maui, Hawaii, pp. 175-200.

    Swift, M. R., M. Palczynski, K. Kestler, D. Michelin B. Celikkol and M. Gosz (1998). Fish Cage Physical Modeling for Software Development and Design Applications. In: Nutrition and Technical Devel. of Aquaculture. Proc. of the 26th U.S.-Japan Aquaculture Symp., UJNR Technical Report No. 26, UNH/UM SeaGrant, Kingman Farm, University of New Hampshire, Durham, NH. Rpt UNHMP-CP-SG-98-19. pp. 199-206.

    Tsukrov, I., O. Eroshkin, D. Fredriksson, B. Celikkol (2001). Finite Element Simulation to Predict the Dynamic Performance of a Tension Leg Fish Cage. Open Ocean Aquaculture IV, June 17 - 20, St. Andrews, NB, Canada, Mississippi-Alabama Sea Grant Consortium, Ocean Springs, MS. MASGP-01-006, 2001 (submitted).

    Tsukrov, I., M Ozbay, D.W. Fredriksson, E. Muller, M.R. Swift, and B. Celikkol (1999). Offshore Grid Mooring/Net Pen System: Finite Element Analysis. OMAE99-3065. In: Offshore Mechanics and Arctic Engineering '99. Proceedings of the 18th International Conference. St. John's, Newfoundland Canada: ASME.

    PhD Dissertation and Master Degree Thesis Publications
    Fredriksson, D.W, (2001). Open Ocean Fish Cage and Mooring System Dynamics. Ph.D. Dissertation submitted to the University of New Hampshire in partial fulfillment of the Engineering Systems Design Program. Durham, NH, 296 p.

    Gace, L.R. (1996). Predicting Response of Submerged Aquaculture Pens to Wave Action using Scale Models. Master's Degree Thesis submitted in partial requirement for the Ocean Engineering degree program. University of New Hampshire, Durham, NH. 156 p.

    Muller, E. (1999). Development of an Offshore Aquaculture Site. Master's Degree Thesis submitted in partial requirement for the Ocean Engineering degree program. University of New Hampshire, Durham, NH. 158 p.

    Ozbay, M. (1999). Finite Element Analysis of Offshore Net Pen/Mooring Systems. Master's Degree Thesis submitted in partial requirement for the Mechanical Engineering degree program. University of New Hampshire, Durham, NH. 111 p.

    Palczynski, M.J. (2000). Fish Cage Physical Modeling. Master's Degree Thesis submitted in partial requirement for the Ocean Engineering degree program. University of New Hampshire, Durham, NH. 111 p.

    4. Technical Reports
    Irish, J.D., W. Paul, W.M. Ostrom, M. Chambers, D. Fredriksson, and M. Stommel (2001a). Deployment of Northern Fish Cage and Mooring, University of New Hampshire-Open Ocean Aquaculture Program Summer 2000. Woods Hole Oceanographic Institution, Technical Report WHOI-2001-01. p. 57.

    Irish, J.D., M. Carroll, R. Singer, A. Newhall, W. Paul, C. Johnson, W. Witzell and G. Rice, (2001b). Instrumentation for Open Ocean Aquaculture Monitoring. Woods Hole Oceanog. Inst., Tech. Rept. WHOI-2001-15, 95 p.

    Tasks and activities for next reporting period

    Tasks for the next reporting period
    Modeling, Monitoring, Engineering Analysis. UNH and WHOI will continue to collaborate in an effort to further understand the dynamics of the fish cage and mooring system to wave and current forcing. One option is to use two accelerometer packages, one in the submerged cage in the floating feed buoy. This testing scenario will enable the engineers to examine the relative motion between the submerged cage and the feed buoy for comparison with the data set obtain this year with the cage at the surface. Analysis will also include additional computer model simulations incorporating the consistent net model developed this last year. Results will be presented and published in peer reviewed conference proceedings and journals.

    Optimal System Design. Extensive physical and computer model tests will be conducted using the SADCO-Shelf submersible cage system. The tests will include monochromatic and random wave simulations. The random wave simulations will be based upon field data collected during one of the extreme events in March, 2001. Transfer functions will be calculated and the performance of the SADCO-Shelf system compared with the deployed fish cage and mooring system at the demonstration site.

    Anchor Systems. The gravity anchor with ballast control will be tested during a long term deployment as part of one of the guard buoys currently deployed at the site.

    Feed Systems. Both of the feed systems deployed as part of this years work will be optimized for efficient feed metering. Attachment and mooring systems will also be assessed considering elastic hose and tether technology. Long-Line Modeling. Since the long-line numerical model has already been developed, it can be readily used on an "as need" basis.

    Work plan to accomplish tasks
    Modeling, Monitoring, Engineering Analysis. As part of the Monitoring, Modeling and Analysis task, the wave rider buoy will be overhauled and incorporated with the environmental instrumentation. The system will contain UNH and WHOI sensors to measure surface waves, water currents, temperature and salinity (at 3 locations) and mid-water fluorescence and turbidity (see monitoring progress report).

    Optimal System Design. The entire list of cage and mooring specification will be obtained for the SADCO-Shelf system modeling studies for construction of the physical model and representation with the numerical model. Submersible load cells will be also be fabricated for the UNH wave tank tests.

    Anchor Systems. For the long term test of the ballast control dead weight anchor, mooring system hardware will be purchased for assembly and deployment.

    Feed System. The load cell recorders and accelerometer package will be refurbished and new instrumentation for the feed buoy, including motion sensor and feed hose load cell fabricated for deployment.

    Concerns or difficulties
    The installment and operation of offshore aquaculture is a complex multidisciplinary task. The exposure to devastating storm events is threatening each installation offshore, and there is risk of destruction of the cage systems due to serious storms. There is considerable excitement in the development of open ocean aquaculture, and insufficient understanding. The interaction between the cultured fish species and the confining net cage is multifaceted and difficult. The long term success of open ocean aquaculture depends on continuing research to broaden the needed knowledge base. Difficulties in its progress are unavoidable, but the chance of success is greatly enhanced though efforts like the OOA Program.

    Expenditures
    Expenditures to date are all within budget.



    • Copyright 2007, Atlantic Marine Aquaculture Center, Durham, NH 03824
    The Atlantic Marine Aquaculture Center is a partnership of the University of New Hampshire (UNH) and the National Oceanic and Atmospheric Administration (NOAA).