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Open Ocean Aquaculture Engineering

CINEMar/Open Ocean Aquaculture Annual Progress Report for the period 1/01/02 through 12/31/02

Principal Investigator(s): B. Celikkol, M.R. Swift, K. Baldwin, I. Tsukrov, D.W. Fredriksson

Center for Ocean Engineering
University of New Hampshire

I. ACCOMPLISHMENTS

A. Scheduled Tasks
Background: The development of technologies and engineering methods is essential if the United States is to establish an economically viable open ocean aquaculture industry and compete on an international scale. Through the Open Ocean Aquaculture (OOA) demonstration project at the University of New Hampshire (UNH), fish cage and mooring systems have been designed using numerical and physical models, built and deployed at an exposed site south of the Isles of Shoals in the Gulf of Maine (Muller, 1999; Tsukrov et al., 2000; Fredriksson et al., 2000; Baldwin et al., 2000; Irish et al., 2001). The site and equipment is being used as an open ocean laboratory to fully examine the deployed system to understand hydrodynamic properties and the response to oceanic forcing (Irish et al., 2001; Fredriksson et al., 2003a; Fredriksson 2003b). Using knowledge gained from this research, the physical and numerical modeling techniques are evolving to reflect the dominating physical processes (Palczynski, 2000; Fredriksson, 2001; Tsukrov et al., 2003). Even though the techniques and engineering methods are being developed, however, engineering challenges still have to be overcome to develop the technological basis for commercial scale aquaculture.

Objectives: To address these challenges the goal of the OOA project has been set to establish a commercial scale facility at the Isles of Shoals site. The engineering component supports this collective goal by pursuing the following objectives,

a. Investigation of commercial-scale fish cage systems,
b. Expansion of the existing mooring grid system at the OOA site and
c. Feed buoy development including design, control/telemetry and modeling.

To successfully accomplish these objectives, the numerical and physical modeling tools and input parameters must continue to be developed as the systems become more complicated. For instance, the numerical model must be improved to include non-linear components (which is included in the previous three objectives). Also, both the physical and numerical models must better represent the nets of the system, and the input wave forcing characteristics at the site better understood. Therefore, in addition to the objectives listed above, the following complimentary goals were initiated,

d. A net panel study to investigate drag and mass characteristics clean and bio-fouled nets, and
e. A wave measurement buoy validation study.

In the following section, a brief description of each of these studies is included. Since the results are extensive, references are incorporated where applicable.

B. Progress on Tasks
Progress on task #1: Investigation of Commercial Size Systems
SADCO-SHELF: The analysis of commercial scale fish cage and mooring systems was initiated with the REFA tension leg system as described in the 2001 yearly progress report and in Baldwin et al. (2002) and Tsukrov et al. (2003b). Next, the commercially available SADCO Shelf© fish cage and mooring system was investigated for potential open ocean use using numerical (using AquaFE) and physical models. With these models, shown on Figure 1, tests were conducted in a variety of conditions using both regular and random waves in surface and submerged deployment positions. The cage was subjected to sets of regular waves with periods ranging from 2.4 to 12 seconds, and a random sea typical of coastal New Hampshire with a significant wave height of 3.5 meters. A detailed description of the entire analysis and results is provided by Decew (2002).

Assuming a linear system, the motion response of the fish cage in heave, surge and pitch and the load response of the mooring lines was analyzed to predict the cage dynamics in the open ocean. In general, the surface models predicted a damped system, which is ideal for a fish cage in the open ocean. This will reduce the stress present on the cage and mooring system, as well as the fish.

The greatest heave response of the system occurred at the lower wave frequencies, notably at 0.083 Hz. The physical model displayed a high surge response from 0.1 Hz to 0.2 Hz, but the cage retained its shape remarkably well. The orientation of the SADCO tension lines and ballast system kept volumetric stability throughout the applied wave frequencies in both models. The models had minimal pitch response throughout the applied frequencies. The tension in the anchor lines, without a current, is acceptable at 40 kN shown in the numerical model under the design wave with a period of 8 seconds and a height of 9 meters. The surface loads under a current (1 m/s at the surface, linearly reducing to 0.25 m/s at the bottom), as shown in the numerical model, with a tension of 160 kN may push the operational limit of the anchors and mooring lines.

The submerged cage models, on average, displayed 40% to 50% less movement than the surface cage models. This is expected due to less wave energy present at depth. The models predicted an overdamped system at depth throughout the wave energy spectrum. The numerical model predictions of tension in the mooring lines also dropped considerably when the cage was submerged, dropping 69% and 75% in the anchor and bridle line load, respectively, under the design wave.

Upon evaluation of the test results, the SADCO system would be able to withstand the normal environmental conditions present in the Gulf of Maine. Under extreme conditions, such as waves similar to the UNH design conditions (consisting of a nominal 9-meter wave, with a period of 8.8 seconds), the cage would have to be submerged due to the large loads present on the mooring system. Future numerical model testing of the physical model can be performed to investigate the effects of the different mooring configurations used in the model tests. Testing is also needed to evaluate the anchors holding strength versus the applied load. The tension in the anchor lines should be investigated to see if the anchors will pull out of the sediment and shift the 3 point grid system. This could have profound effects on the dynamics and strength of the mooring system if an anchor is displaced. This cage should be compared to other offshore cages to determine the most economical, robust and reliable system for use in the open ocean.

Tension Leg Mooring with SeaStation 3000: Another commercial size fish cage and mooring system considered in the last year was an adaptation of the Sea Station 3000 (SS3000) designed by Ocean Spar Technologies (OST) in Bainbridge Washington. Discussions with OST to modify the SS3000 to incorporate feeding and harvesting systems resulted in a proposal opportunity with the Advance Technology Program with Great Bay Aquaculture (GBA). A schematic of a potential configuration is shown on Figure 2 (left side).

One mooring system being considered consists of a four-point tension leg grid configuration with compliant members to enable the cage move partly with the seas, but stiff enough to maintain station. This work is building upon past research investigating tension leg moorings described in Savage et al., (1997) and Fredriksson et al., (1999). In this study, however, the mooring includes a compliant component consisting of a new technology utilizing strong, high stretch hoses. This concept has been considered for oceanographic moorings (though never used), but has never been incorporated in a fish cage mooring. A preliminary computer model (right side of Figure 2) has been constructed of the SS3000 cage with the extended spar feeding mechanism. Simulations have shown that this configuration shows considerable promise of a simple, small footprint mooring system with compliant hoses, which can withstand the harsh environmental conditions.

PROGRESS ON TASK #2: Expansion of Mooring System Grid
To establish a commercial size facility at the OOA site, the existing independent grid systems have to be expanded. Presently, the two configurations that are being considered consist of combined 3- and 4-grid mooring systems. This represents an extension of work previously done by Ozbay (1999) and Tsukrov et al. (1999) where 2-grid moorings were investigated. In the last year, however, additional numerical models were built incorporating the new mooring system configurations with models of the existing Sea Station 600 m3 cages (SS600) and the SS3000 cages. Finite Element Analysis (the AquaFE program) was used to predict the dynamic response of these new systems under the UNH design conditions. Information on the dynamics of motion, displacements of critical nodes and stress fluctuations on the critical mooring lines is used to estimate the overall performance of the system and compatibility of the SS600 and SS3000 cages with new mooring designs. In this study the response of the system was investigated in both surface and submerged positions of fish cages.

3-Grid Mooring System Numerical Model: The numerical model of the 3-grid mooring system configuration, as shown on Figure 3, was constructed in AquaFE. The model incorporated three fish cages including the two SS600s and one SS3000. The mooring system components were chosen to be similar to those presently deployed at the site (see Muller 1999 and Fredriksson 2001 for details). The overall area for this mooring design is approximately 105400 m2 when projected on the sea bottom.

The system uses 12 anchors attached to the structure and assumed to be fixed for the modeling simulations. The anchor chain is modeled as 12 truss elements and the anchor lines as 8 connected truss elements. The direction of the anchor lines is perpendicular to the grid mooring which forms a 19 degree angle with the seafloor. The triple horizontal grid is 37-m. above the bottom and is composed of 3 equivalent (65-m x 65-m) squares that are modeled as 4 truss members for each side of the square. There are 8 buoys attached on the corners of the squares which causes pretension on the triple squared grid assembly (approximately 5500 N buoyancy force each buoy). The bridles are each modeled using 4 truss elements. The system was modeled in both surface and submerged configurations and the results compared. An example of the system deformation (side view) is shown on Figure 4.

4-Grid Mooring System Numerical Model: A second mooring design considered for the demonstration project is a 4-grid system as shown on Figure 5. Once again a numerical model was built using components similar to those presently deployed at the site. This model, however, includes two SS600 and two SS3000 fish cages. The geometry of the mooring system was similar to that of the 3-grid configuration, except with four squares. Simulations were performed in the surface and submerged configurations using the UNH design condition.

It should be noted that this portion of the research is ongoing and therefore the preliminary results are not presented. The model simulations are only one step of the design process that provides an estimation of the dynamic response of the fish cages and mooring line forces. Using these results, each of the mooring system components including lines, anchor and fasteners (i.e. shackles) will be scrutinized for survivability under the design conditions.

PROGRESS ON TASK #3: Feed Buoy Development
Design: Another major component of establishing a commercial size facility at the OOA site that needs to be developed is an automated feeding system. Especially since, a reliable method of supplying regulated feed to fish in submerged fish cages in the open ocean environment is not commercially available in the United States. Considerable effort to develop a small-scale feed system to reliably supply feed to submerged cages in the harsh marine environment of the Gulf of Maine has been ongoing by researchers throughout the OOA project. One of the systems being consider utilizes a surface buoy, moorings attached to the grid system, a feed transfer hose, feed dispensing and telemetry/control systems.

In the fall of 2001, a prototype "feed buoy" was deployed at the OOA site shown on left side of Figure 6 with the dimensions shown on the right side. The original feed buoy had a simple feeding mechanism relying upon gravity to carry the feed to the cage though a loose hose at timed intervals. Periodic clogging of the hose and timer malfunctioning were fundamental issues associated with this first generation of feed system, though the survival of the shell and components were promising.

In the summer of 2002 the buoy was recovered for a general overhaul and reconfiguration with a number of improvements. In the winter of 2002, the second generation feed buoy system will be deployed. The buoy will be moored with compliant elastic mooring lines, and a taut rubber high-stretch hose, which connects the feed buoy to the submerged fish cage. It will also include an additional custom made flotation ring (left side of Figure 7) To reduce feed clogging in this rubber stretch hose, the buoy will be moored with elastic tethers to keep the feed hose taut and a new check valve assembly incorporated (see right side of Figure 7). The system also uses a small water pump to actively pump the feed. The buoy system also incorporates wind and solar power generation (as well as charging from supply vessel) to provide for the increased power demands of the pumps and valves. The simple timer was replaced with a more sophisticated control system that will switch the power to the various pumps on a user set schedule, and also monitor the operation of the whole system (charging, power drain on each circuit, battery condition, etc.). The system controller will utilize a spread spectrum radio to send diagnostic and status information to shore and via the internet to the project manager. This link will allow for some control of the offshore system from the managers desk. The high-stretch feed hose has integrated conductive wires to send power down and receive data back from instrumentation in the fish cage. The first measurements will include temperature, salinity along with two video cameras. The video signals will be sent to the buoy, digitized then transmitted by wireless Ethernet to shore where the manager will be able to observe the fish during the feeding operation. Finally, for engineering studies and system monitoring, a load cell will be integrated into the feed hose and used in conjunction with a motion package inside the buoy and another inside the fish cage. This instrumentation will be used to collect data, which will later be compared to finite element analysis modeling performed on the cage/buoy interaction. This will assure that the fish cage, stretch hose, feed buoy mooring is optimally designed and operating properly.

Modeling: Computer models of feed buoy system are being developed to assess force and motion dynamics so that components and design can be chosen to withstand the high-energy environment of the demonstration site. The finite element model of feed buoy is presented in Figure 8. A nonlinear truss element (with piecewise linear elastic properties) was implemented to model feeding hose elastic behavior.

To adequately predict the tensions in the mooring lines, especially under extreme loading conditions, it is very important to accurately model inertia, buoyancy and hydrodynamic forces acting on the feed buoy. The drag force is proportional to projected area, but buoyancy and inertia are proportional to volume of the buoy. Thus set of truss elements can not exactly reproduce the forces acting on the feed buoy. Three different models of the feed buoy were used in the computer simulations (1) Model 1 has exact drag, but inertia and buoyancy are underestimated (2) Model 2 has exact inertia and buoyancy, but drag is overestimated (3) Model 3, based on compromise between first two models, has slightly underestimated inertia, buoyancy and slightly overestimated drag. The dynamic performance of the feed buoy system with various mooring line designs was investigated for both typical and extreme environmental loading conditions. Under typical loading conditions (1.2 m wave and constant current 0.25 m/s) position of feed buoy is very stable and tensions in mooring lines are small (Figure 9).

The design condition consists of a nominal 9-meter wave (with a period of 8.8 seconds) and a current, which is set to change linearly from 1 m/s on the surface to 0.25 m/s near the bottom. The finite element simulations show that this extreme environmental loading results in large deformations and tensions that are higher than maximum working load for rubber tether (170 lb), see Figures 10, 11 and 12, for models 1, 2, and 3 respectively.

PROGRESS ON TASK #4: Net Drag Study
In addition to the modeling work performed in support of the OOA site expansion and feed buoy design, research has continued to investigate some of the physical processes that affect the design of open ocean aquaculture systems. The drag due to waves and currents on the net component of a fish cage is one of the primary design concerns, for example, see Palczynski (2000) and Fredriksson et al. (2003c). In the last year measurements were made of steady state drag force acting on one-meter-square net panels, oriented at normal incidence, for tow speeds ranging from _ to 2 knots. Experiments were done for clean, fish cage netting in the UNH 120 foot long tow tank, while testing of biofouled panels was conducted in the field. Panels consisted of one-inch-square mesh, 1/8-inch-diameter thread netting tightly stretched within a square frame of one inch PVC pipe. Experiments were also done for the frame only, so drag force on just the netting could be inferred. Measurements were made using a 50 lb. capacity Interface Super Mini load cell (model SM-50) connected by thin fish line to a tow bridle arrangement.

Bio-fouled panels were generated by exposure at the open ocean aquaculture site south of the Isles of Shoals, New Hampshire during the winter of 2001-2002. Drag testing in the field was done using a non-powered catamaran towed alongside a small research vessel. The panel mounting configuration was exactly the same as that used with the tow carriage in the tank tests.

Results of 134 tow experiments (including duplicates) were processed to yield force as a function of tow speed and drag coefficients. For the one-meter-square net (only), the force at two knots was 42 lbs. The average drag coefficient based on actual net thread projected area was 1.175, while the drag coefficient based on net outline area was 0.279. For netting slightly fouled with small mussels, the drag coefficient based on thread area was 2.032, while drag coefficient based on outline area was 0.754. The corresponding values for netting heavily fouled with algae were 4.247 and 1.576, respectively.

In a complimentary effort, a study has been initiated to measure the effectiveness of various coatings (provided by E-paint) on reducing drag force due to current on nets subject to bio-fouling. The approach is to measure drag of "clean" panels in the UNH tow tank, deploy the panels at the OOA site, and re-measure drag force as a function of current after recovery. Seven one meter by one meter panels are being used including both coated and uncoated nets. The panels were tank tested shortly after delivery to UNH Ocean Engineering near the end of August, 2002. They were deployed at the OOA site on September 20, 2002. Recovery and re-testing will take place in December, 2002 depending on weather and the availability of boats, instrumentation and personnel.

The tank testing methodology was similar to procedures described by Fullerton et al. (2002) for a similar study carried out previously. Preliminary results indicate that "clean” drag coefficients (based on actual projected area) are in the vicinity of 1.2. This value is realistic since cylindrical drag coefficients within the test Reynolds number range are about 1.2, and the net panels are effectively made up of superimposed cylinders.

Testing of the recovered net panels will have to be done in the ocean in order to minimize disturbance of the bio-fouling. The at-sea data acquisition system will be mounted on a catamaran-type platform towed alongside the UNH research vessel Bluefin. Measurement procedures similar to those used in the field portion of the Fullerton et al. (2002) study will be employed. Upgrades in panel mounting and data acquisition will, however, be implemented due to the harsher environment expected for winter conditions. Figure 13 shows examples of clean and bio-fouled net panels used in the study.

PROGRESS ON TASK #5: Wave Measurement Buoy Validation
The last component of the engineering project was the analysis of the wave measurement buoy at the site as shown on Figure 14 (left side). This buoy is used to transmit real-time wave information for operational purposes so an accurate data is necessary. A series of laboratory tests were conducted on the buoy to determine its dynamic response. A free release test showed that the natural period of the buoy was 1.27 s and also provided values for the linear coefficient of heave damping, which was 522 kg/s and virtual mass which was 347 kilograms for an analytical model. Using this data an analytical model was developed. The results predicted the natural period of the buoy to be 1.3 s and that the transfer function of the heave of the buoy to surface elevation was one for wave periods greater than 5 s.

The model of the buoy was constructed and tested in monochromatic and random sea wave tests to determine the heave transfer function (see the left side of Figure 14). A free release test was conducted on the model to verify its similarity to the full scale buoy. The natural period found using this test was 1.25 s. Values for the linear coefficient of heave damping and virtual mass were 11% and 3% different, respectively, from the Wave Measurement Buoy. The wave tests conducted on the model buoy showed that the transfer function found by the monochromatic wave tests were all within 10% of one. The random sea tests showed that the transfer function of the buoy was one for wave periods between 2 and 5 seconds. Figure 16 (left side) shows a plot of all RAOs and natural frequency results from the tests.

The Wave Measurement Buoy was deployed and retrieved three times during an eleven month trial period. The data obtained during this period was processed with a modified NDBC method and compared to nearby NDBC wave buoys. Differences in the wave spectra necessitated the use of a more local measurement for verification of the accuracy of the Wave Measurement Buoy. This was accomplished with a pressure sensor and an ADCP with a waves processing package and mooring (see Figure 15). Data sets from the pressure sensor were inconclusive but the ADCP provided accurate results. These data sets were compared to those obtained with the Wave Measurement Buoy. Differences in the compared wave spectra are attributed to low frequency noise. The removal of this noise is possible with the use of a Butterworth high-pass filter, which must be tuned specifically for each wave record. A processing algorithm that located a transition point in the data where the signal to noise ratio became greater than one was applied to the data. This method avoided the low frequency noise and could be applied to all data sets without modification. The results for significant wave height from this method are shown in Figure 16 (right side). The RMS error of the Wave Measurement Buoy significant wave height when compared to data sets from the ADCP is 21%, which is reasonable, but can be improved upon.

C. Important Results
Results are incorporated above.

D. Difficulties Encountered
No major difficulties encountered, other challenges are described above.

E. Anticipated Success in Meeting Project Objectives in the Schedule Project Period
See Section II below.

F. Reports, manuscripts and presentations resulting from project
Reports and manuscripts are included in the body of the report as reference material. Several presentations were made as described after the reference section below.
REFERENCES
Ahern, J. (2002). Validation of Wave Measurement Buoy. Master’s Degree Thesis submitted in partial requirement for the Ocean Engineering degree program. University of New Hampshire, Durham, NH. 101 p.

Baldwin, K.C, Celikkol, B., Chambers, M., Fredriksson, D.W., Irish, J.D., and M.R. Swift. (2002) Open Ocean Aquaculture Engineering. Proceedings of the Oceans 2002 Conference. Biloxi, Mississippi.

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.

Decew, J. (2002). Numerical and Physical Modeling of the SADCO-Shelf Submersible Fish Cage. Master’s Degree Thesis submitted in partial requirement for the Ocean Engineering degree program. University of New Hampshire, Durham, NH. 267 p.

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.

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, September 2001.

Fredriksson, D.W., M.R. Swift, J.D. Irish, I. Tsukrov and B. Celikkol. (2003a) Fish Cage and Mooring System Dynamics Using Physical and Numerical Models with Field Measurements. Aqua. Eng. (In Press).

Fredriksson, D.W., M.R. Swift, J.D. Irish and B. Celikkol. (2003b). The Heave Response of a Central Spar Fish Cage Transactions of the ASME, J. of Off. Mech. and Arct. Eng. (In Press).

Fredriksson, D.W., M.J. Palczynski, M.R. Swift and J.D. Irish. (2003c). 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 (In Press).

Fredriksson, D.W., E. Muller, M.R. Swift and B. Celikkol (1999). Physical Model Tests of a Gravity-Type Fish Cage with a Single Point, High Tension Mooring. OMAE99-3066, In: Offshore Mechanics and Arctic Engineering ’99. Proceedings of the 18th International Conference. St. John’s, Newfoundland Canada: ASME.

Fullerton, B., M.R. Swift and K.C. Baldwin (2002) “Measurement of Drag Force Acting on Fish Cage Net Panels”, Internal Technical Memorandum, Open Ocean Aquaculture Engineering Project, University of New Hampshire, Durham, NH.

Irish, J.D., W. Paul, W.M. Ostrom, M. Chambers, D. Fredriksson, and M. Stommel (2001). 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, N. Witzell, G. Rice and D.W. Fredriksson. (2001). Instrumentation of Open Ocean Aquaculture Monitoring. Woods Hole Oceanographic Institution, Technical Report WHOI-2001-15. p. 95.

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.

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.

Tsukrov, I., Eroshkin, O., Fredriksson, D. W., Swift, M.R. and Celikkol, B., (2003a). Finite element modeling of net panels using consistent net element. Ocean Eng. 30: 251-270.

Tsukrov, I., O. Eroshkin, D. Fredriksson, B. Celikkol (2003b). 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 (In Press).

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.

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.

PRESENTATIONS
Aquaculture America 2002 Conference: Field Measurements of the Forcing and Response of an Open Ocean Aquaculture Fish Cage and Mooring System presentation by D.W. Fredriksson at the Aquaculture America 2002 Conference in San Diego California on January, 28 2002.

Aquaculture America 2002 Conference: Dynamic Response of Net Elements in Offshore Fish Cages presentation by I. Tsukrov at the Aquaculture America 2002 Conference in San Diego California on January, 28 2002.

Marine Technology Society/New England Section Presentation: Open Ocean Aquaculture Engineering presentation by D.W. Fredriksson conducted May 22, 2002 at the Seacoast Science Center in Rye, NH. The meeting was organized by Professor Kenneth Baldwin.

American Society Mechanical Engineers/Offshore Mechanics and Arctic Engineering Conference: The Heave Response of a Central Spar Fish Cage presented by D.W. Fredriksson on June 27, 2002 in Oslo, Norway. D.W. Fredriksson also served as the Co-Chair of the Aquaculture Engineering Session

IEEE/OCEANS 2002 Conference: Open Ocean Aquaculture Engineering presentation by K. Baldwin in October. Biloxi, Mississippi.

II. TASKS AND ACTIVITIES FOR THE NEXT REPORTING PERIOD

A. Tasks for next reporting period
Please note that many of the tasks and activities evolve throughout the year. However, a general guideline is provided below.

Investigation of Commercial Size Systems: This portion of the project is ongoing. For the next reporting period the SS3000 numerical model will continue to be used in the modeling efforts to expand the site. In addition, large gravity type cages will also be investigated for applicability in the Open Ocean.

Expansion of Mooring Grid: Additional computer model iterations of the 3- and 4-grid systems will be performed using various mooring materials to specify the necessary components. The design procedure will include applying standard catenary equations to size anchor chain and grid flotation.

Feed Buoy Development: Working closely with the operations group of the project, the new buoy design will be deployed and tested. The communication links will also be a focus of next years work. One of the goals is to have an interactive interface (i.e. two-way communication) with observatory platforms at the site. Plans are also being made to further collaborative efforts with Ocean Spar Technologies to develop a commercial-size feeding spar.

Net Panel Study: This portion of the engineering work at the COE has also evolved to be a collaborative effort with scientists at the Jackson Estuarine Laboratory and E-Paint. Collectively, this group is proposing to expand the study in Phase 2 of a Small Business Innovation Research project for 2003.

Wave Measurement Study: The most important tasks of the wave measurement study to be performed in 2003 are to finalize the wave processing algorithm and provide the real-time data publicly.

B. Brief work plan to accomplish these tasks
Investigation of Commercial Size Systems: Since it is likely that the next commercial size system to be investigated will be some form of a plastic gravity cage (i.e. HDPE), it will be necessary:

  1. To obtain all of the physical properties of the material
  2. Define a typical shape, for example with it be an 80-, 90-, or 100-meter circumference cage (or other).
  3. Incorporate a suitable model into the AquaFE program.
  4. Investigate finite element modeling programs for analyzing structural integrity of the cages.

Expansion of Mooring Grid: To continue the development of the mooring grid system, the following will need to be performed:

  1. Define design criteria.
  2. Acquire quotations from mooring companies, GaelForce and Cards Aquaculture, etc
  3. Obtain material and geometric properties of potential mooring components.
  4. Perform catenary equation analysis.
  5. Perform computer model simulations.
  6. Price components

Feed Buoy/Spar Development: Working with operational staff of the OOA project, the buoy design will be:

  1. Assess all of the internal mechanisms
  2. Develop two way communications with buoy
  3. Obtain motion response measurement of buoy (collaborative effort with WHOI)
  4. Obtain feed hose tensions in buoy (collaborative effort with WHOI)

The commercial-size feed buoy/spar development will include personnel from UNH, Ocean Spar Technologies and ETI (maker of feed mechanisms). Plan will include:

  1. Submit a joint SBIR proposal.
  2. Perform initial design during Phase I of effort.
  3. Present data for Phase II for January of 2004.
  4. Prepare full proposal.
Net Panel Study: The next step of the Net panel study is to work with scientist at the Jackson Estuarine Laboratory (JEL) and E-Paint to submit a Phase II study to SBIR. In this study, the engineering component will include:
  1. Expand the existing scope to include more net panels for drag investigation.
  2. Optimize net frame design to make the area smaller.
  3. Design deployment configuration at the site.
Wave Measurement Study: Brief work plan will include:
  1. Finalize processing algorithm.
  2. Redeploy buoy optimizing location of accelerometers.
  3. Establish real-time data on a website.

B. Concerns or difficulties
No major concerns or difficulties.

III. 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).