In this issue... Newsletter of Oceanic Consulting Corporation Spring/Summer 2007

Transcription

1 Newsletter of Oceanic Consulting Corporation Spring/Summer 2007 COSSACK PIONEER RISER COLUMN SURVIVABILITY The impact of global warming is beginning to be seen throughout the world. The increased frequency and intensity of hurricanes and cyclones, noticed since the mid-1990s, has concerned many operators of offshore platforms throughout the world and has led many to review the survivability of their offshore assets in light of increased environmental loading. Woodside Australian Energy contracted Oceanic to perform survivability seakeeping experiments on the riser column of the Cossack Pioneer FPSO, which is located in 81 meters of water off the northeast coast of Australia. Originally, the column was designed to survive in a 100-year storm with a significant wave height of 11 meters, but this wave height has since been revised to 14.3 meters. As a result, Woodside wanted to determine how much these larger waves could affect the riser. Experiments on a 1:50.6 scale model riser column were carried out in the Offshore Engineering Basin at the Institute for Ocean Technology. The model was fitted with an instrumented, eight-leg, catenary mooring and nine instrumented risers as well as an optical tracking system to measure column motions. Wave and current experiments were performed for various sea states, current velocities, and wave directions in order to evaluate the riser column motions and mooring line characteristics. In this issue... Cossack Pioneer Riser Column Survivability Charting the Course: Spring/Summer 2007 Evaluation of VIV Suppression Fairings for Thunderhorse Numerical Simulation of Iceberg Collision with Spar Collaboration in the Americas Ice Engineering Solutions for the Petroleum Industry Ongoing Investigations of a Wave Piercing Bow Concept Time Domain Prediction of VIV Profile: Tim Moore Smooth Sailing: Oceanic Reaches New Agreement with NRC Oceanic Assumes Operation of Testing Facility in Vancouver, BC Feature: VIV Test Apparatus

2 SPRING/SUMMER 2007 CHARTING THE COURSE 1 W ithout a doubt, you all have heard that the Arctic is heating up, both figuratively and literally. Every day, numerous examples of global warming are appearing, but nowhere in the world is this trend more evident than in the high Arctic. For offshore operators attempting to explore for and extract resources from the Arctic, this environment presents numerous unique challenges such as: extreme cold temperatures, sensitive environmental issues, long periods of darkness, complicated logistics, and extreme loading caused by ice. With the United States Geological Survey stating that as much as 25% of the world s remaining petroleum resources are likely to be found in the Arctic, the need to develop natural resources north of 60 has accentuated the demand for engineers who understand northern operations. Through its niche expertise in design evaluation in ice-infested and arctic waters, Oceanic Consulting Corporation is assisting those that need to navigate vessels and operate equipment in the harsh Arctic environment Reduced Velocity (Vr) Amplitude Ratio (A 4 With access to the world s longest towing/ice tank, Oceanic is a portal to some of the world s best facilities and personnel for Arctic engineering. To date, over 1000 ice sheets have been grown in the ice basin, resulting in an extensive database of performance data for ships and offshore structures. Oceanic s Vice President of Technical Development, Mr. Don Spencer, is at the forefront of our Ice Engineering team. Mr. Spencer has been a leading ice researcher since 1985 and has produced well over 100 technical reports and research papers on ice-related topics. He was also instrumental in Oceanic s acquisition of DECICE, a numerical code which models ice pieces as discrete elements that can bump and collide, break apart, and form new elements. A brief article describing Oceanic s DECICE simulation of an iceberg colliding with a spar can be found in this edition of Making Waves. DECICE has been applied successfully to a large number of diverse ice engineering problems, including ice loading on a singlepoint-mooring buoy, loading on an upward breaking bridge pier, pack ice arching between bridge piers, and buckling of ice floes under lateral pressure. Additionally, Oceanic is currently working with the Centre for Marine Simulation (CMS) at Memorial University to integrate DECICE with a ship maneuvering code that will have a 360 real-time visuals. This development will produce an advanced ice navigation simulator that is capable of providing realistic training for mariners performing tactical operations in ice. In this edition, we ve also focused on projects that were recently completed for the offshore industry including a riser column survivability study, the evaluation of vortex induced vibration (VIV) fairings, and the numerical prediction of VIV. Oceanic has developed both high and low Reynolds number VIV test apparatuses. These devices can be used to conduct a wide range of experiments that include determining the effect of flow turbulence on VIV, quantifying the performance of VIV suppression devices such as strakes and fairings, and examining the effect of fouling on riser stability. You can obtain a specification sheet for the VIV equipment by contacting our office or accessing our website. Also included in this issue is an overview of some aspects of ice testing that have been applied to petroleum industry challenges. Such challenges can involve vessel movement, protection of surface and sub-surface petroleum equipment, or evaluation and improvement of emergency evacuation systems and equipment. Regardless of the type of problem, Oceanic has the capabilities and expertise that can lead to efficient and novel solutions. With innovative solutions and solid cutting-edge engineering practices, there are no limits to where petroleum exploration and production can go. There really aren t any limits for Oceanic, either. For Oceanic Consulting Corporation, and with best regards, Dan Walker, Ph.D, P.Eng. President For additional details on any of the projects highlighted in this edition, please contact: J. Michael Doucet Senior Naval Architect Consultant, Ship Performance michael_doucet@oceaniccorp.com Lee Hedd Senior Naval Architect Consultant, Ships & Yachts lee_hedd@oceaniccorp.com Don Spencer Vice President Technical Development don_spencer@oceaniccorp.com

3 EVALUATION OF VIV SUPPRESSION FAIRINGS FOR THUNDERHORSE High Reynolds number VIV test apparatus. Oceanic Consulting Corporation was contracted by the Thunderhorse project team to complete an evaluation of two commercial riser fairings for the suppression of Vortex Induced Vibration (VIV). The competing fairings were tested headto-head over a two-week period. A Dual Fin Splitter (ADFS) fairing was provided by AIMS International of Houston and a short teardrop fairing was supplied by Trelleborg Offshore of the UK. Representatives of each company were in attendance as their respective design was being tested. Prior to these experiments, both manufacturers conducted extensive test programs to evaluate concepts and perform design optimization using Oceanic s sub-critical Reynolds number test facility installed in the 58-meter Towing Tank at Memorial University. These experiments allowed each manufacturer to rapidly, and cost effectively, evaluate many design options before committing to a final prototype design, which was subsequently manufactured and tested using the high Reynolds number facility. The high Reynolds number experiments were conducted in the 200-meter Towing Tank at the Institute for Ocean Technology. Prior to testing each fairing, bare rough pipe experiments were conducted to ensure that the test apparatus was functioning correctly. These validation experiments were consistent and compared favourably with similar experiments conducted as part of the DeepStar JIP in 2003/2004. Both fairings were tested in a single degree-offreedom free vibration mode, covering a Reynolds number range of 200,000 to 1.4 million. Four different spring settings were used for each test series, and the nominal reduced velocity covered a range of 3 to 20. All tests used a pluck method, where the cylinder was initially offset from its equilibrium position and then released to provide initial excitation. The output of the test program was the standard amplitude ratio, A*, versus nominal reduced ratio, U*, curves. As well, the drag coefficient for the fairings was found from both the free VIV tests and from experiments where the cylinder was fixed. Both fairings had very good motion suppression characteristics relative to the bare pipe and drag coefficients which were substantially less than those of other VIV suppression devices such as strakes. RESPONSE OF MOORINGS &SPARS NUMERICAL SIMULATION OF ICEBERG COLLISION WITH SPAR Oceanic Consulting Corporation has recently simulated the collision of a moored 80,000- tonne Spar with large icebergs for FloaTEC of Houston as part of their ongoing research into ice capable structures. The numerical timedomain simulation was completed using the 3-dimensional version of DECICE. In DECICE, both the iceberg and the Spar were treated as discrete elements, each with six degrees-offreedom rigid body motions. Both bodies were floating and incorporated hydrodynamic drag and added mass. The Spar was initially at rest and moored on station by a 12-line non-linear spread mooring system, while the iceberg was given an initial velocity of two knots and struck the Spar head on. The contact geometry was assumed to follow that of a sphere being penetrated by a vertical cylinder, giving a contact area that was elliptical in shape and grew linearly with the penetration depth. A typical ice pressure to contact area function was incorporated to give the ice crushing pressure and resulting load during the interaction events. Three different iceberg sizes were modeled, with masses ranging from 100,000 to 1 million tonnes. Individual time segments from a DECICE animation showing iceberg and riser displacements. COLLABORATION IN THE AMERICAS Oceanic Consulting Corporation has been working in cooperation with several other testing facilities around the world. Recently, Mr. Tim Moore of Oceanic was invited to LabOceano - part of the Federal University of Rio de Janeiro, Brazil - to present work done by Oceanic in the field of pressure measurements for hydrodynamic testing. Oceanic was involved with the initial development of LabOceano s plans for pressure measurement, and has provided LabOceano with details of the pressure sensors used by Oceanic in our work. While visiting LabOceano, Mr. Moore was able to observe, and provide assistance with, the instrumentation of a model for the measurements of slamming loads. This collaborative effort arose from an article on pressure measurement published previously in Making Waves and through discussions between Oceanic President Dr. Dan Walker and LabOceano Adjunct Director Dr. Antonio C. Fernandes. The collaboration has been of great benefit to both parties, and we look forward to further collaborations with our friends in Brazil.

4 ICE ENGINEERING Model of the Terra Nova FPSO in the 90-meter Ice/Towing Tank. ICE ENGINEERING SOLUTIONS FOR THE PETROLEUM INDUSTRY In the present global search for new hydrocarbon deposits, the Arctic is once again receiving a high degree of scrutiny as it is expected that significant reserves may be present in northern regions. This presents a problem for many petroleum industry operators since exploration and production activities in such a harsh environment will require unique solutions to deal with the extremes of cold temperatures and large ice loads. The ice engineering challenges are great for everything that is used in the Arctic, including production equipment, emergency evacuation systems, supply vessels, floating platforms and fixed structures. In fact, even the task of installing infrastructure is more complicated by the harsh conditions found in the Arctic. While these challenges can sometimes seem insurmountable, some very innovative solutions have been developed by those that have experience related to operation in Arctic conditions. Over the years, Oceanic Consulting Corporation and its partners at the Institute for Ocean Technology (IOT) have completed a significant amount of research in the area of ice engineering. While the majority of this work has revolved around physical model tests in the IOT 90-meter Ice/Towing Tank, a large portion of work has also been completed as numerical evaluation studies or full scale field trials. Successful model scale evaluation of design concepts, coupled with focused numerical simulation and analysis, is very cost effective in allowing industry operators to test and refine their designs before building expensive systems. Full scale trials are useful in verifying that designs operate as intended, while also providing information that can be of use for future developments. To assist our present and potential clients in appreciating the manner in which such systems can be successfully evaluated, an overview of various projects undertaken within the Oceanic community is provided here. PHYSICAL MODEL TESTING Using physical testing, Oceanic has conducted research into a wide variety of offshore structures and vessels that are currently deployed in ice environments. Some of these were fixed gravitybased structures (for places such as Sakhalin, Beaufort Sea, Cook Inlet, Caspian Sea, Bohai Bay, and the Grand Banks) while others included tanker loading terminals where vessels are moored to relatively slender towers or buoys. The range of ice environments that have been modeled include level ice, first-year and multi-year pressure ridges, pack ice and pressurized pack ice. On the Canadian Grand Banks, iceberg mitigation strategies have included designing the structure to withstand an iceberg impact (as is the case for the Hibernia platform), making the structure mobile to avoid an impending impact (as is the case for the Terra Nova or White Rose FPSOs), or towing the iceberg away from the structure. The local community has been involved in model scale evaluations for all three of these projects. MODELING FOR FIXED STRUCTURES Fixed offshore structures are generally found in relatively shallow waters. In very shallow water, they are often simply rock berms or artificial islands. As the water depth increases, gravity based structures are employed. Icebergs and pressure ridges represent two of the most significant design challenges to structures that must operate in Arctic environments. For pressure ridges, however, avoidance is impractical, so offshore structures are generally designed to withstand the resulting loads. In such cases, these structures have sloping sides to promote flexural failure, which may be either through upward or downward breaking. An example of a successful physical evaluation of first year ridges are the experiments that were conducted to assess the piers of the Confederation Bridge. The bridge is approximately 13 km long and spans the Northumberland Strait between New Brunswick and Prince Edward Island. Each model ridge was formed from broken ice blocks and was refrozen to form a consolidated layer. As the bridge is celebrating the 10-year anniversary of its opening, this provides a useful testament to the ice engineering design process that was followed. Multi-year ice ridges pose one of the most significant engineering challenges to offshore structures. The ice in these features is very strong since it has warmed and re-frozen over several seasons, which reduces its brine content and

5 bonds the ice blocks together. To correctly model these features, the ice sheet grown in the test basin is cut into strips and carefully submerged and placed under adjacent strips to create layers. The ice is then allowed to re-freeze, making large relatively homogenous ice blocks. Special mechanical tests were developed to characterize the structural strength and elasticity of the model ridges. In one particular test, a downward breaking conical structure was then forced into the ridge causing it to fail in flexure. The measured global loads were compared with analytical models. MODELING FOR FLOATING STRUCTURES AND SHIPS Floating structures are generally found in deeper waters where it is impractical or too costly to use bottom fixed infrastructure. In such cases, the set of challenges requiring assessment is different. As an example, the objective one model test program was to quantify mooring hawser loads on a conventional Panamax tanker while operating in drifting pack ice. Many operational parameters were evaluated including differing ice thicknesses, ice drift speeds, floe sizes, flow concentrations and hawser stiffnesses. One scenario involved a gradual change in ice drift direction. For accurate modeling, the large amplitude planar motion mechanism (PMM) was adapted to tow a tanker model loading terminal at oblique angles, simulating the change in ice drift direction on the facility. In another program, a parametric study was conducted to evaluate the maximum hawser loads acting on a tanker that was moored to a fixed offshore terminal in moving pack ice. Two types of tests were conducted. In the first case the ice drifted from one direction, stopped, and then came from an oblique direction. In the second case, the ice direction was continuously changing. Parameters included: the diameter of the offshore terminal; the floe thickness, size and concentration; and, the ice drift speed and direction. The effectiveness of using ice management around the tanker was also investigated as a means of reducing hawser loads. Another experimental program examined the ice loading of moored offshore platforms, such as semi-submersible drilling platforms and turret moored tankers. This test program studied the effects of ice thickness, drift speed, and ice concentration as well as orientation of the vessel relative to the ice drift direction. The experiments considered fixed vessels and those on moorings. NUMERICAL ANALYSIS Numerical analysis can be completed either as a stand alone investigation, or as part of a more comprehensive program that also includes physical tests. Purely numerically studies are typically completed as part of initial conceptual design evaluations. As one article in this edition already discusses iceberg modeling, it will not be repeated here. Other modeling that can be undertaken includes examination of ice fields around fixed structures, such as bridge piers, or around floating systems, such as marine buoys. Results from such modeling provides global ice loads on the fixed structures and the loading and excursion caused by ice on non-fast structures. In addition, these methods can define the influence of the structure on the failure of the local ice sheet. Oceanic s DECICE ice modeling code was featured in an earlier edition of Making Waves (Winter 2006) and a code description may also be found on our web site. FULL-SCALE TRIALS Depending on the project, full scale trials can take place in the field or in the controlled environment of a test facility. An example of each type is provided below. A full scale segment of marine transfer hose (2.0 m long x 1.0 m diameter) was tested in a 25 cm thick ice sheet grown in the controlled facilities of the 90-meter Ice/Towing Tank. The test was undertaken to determine if the hose abraded or was otherwise damaged by continuous impact and pinching that resulted from movement of the sample against the artificially roughened edge of the ice sheet. Normal loads, in excess of 2 tonnes, were provided by a hydraulically actuated plate that simulated the ship hull. To assess the impact of bergy bits against ship structures, a full-scale tests was completed in which a Canadian Coast Guard Icebreaker, the CCGS Terry Fox, purposely collided with small icebergs to enable ice-hull interaction forces to be measured. Bergy bits are house-sized icebergs that are formed from glacial ice. They are difficult to see in certain environmental conditions, often going undetected by onboard radar, and pose a significant threat to ships operating in ice. For this trial, instrumentation included an external impact panel and 120 strain gauges, welded onto the inside of the hull, to measure forces and pressures during the ice impacts. These experiments were supplemented with tests in the 90-meter Ice/Towing Tank, where the impact of car-size growlers was studied using a specially designed impact apparatus. While these projects highlight a limited crosssection of the work that has been undertaken in the Oceanic community, they serve to illustrate the diversity of problems that can be assessed and which ultimately can benefit from detailed examination by our experts. If your firm has a future project which must operate in the harsh Arctic environment, Oceanic has the right people and facilities to get the job done. Bridge pier in first-year pressure ridge. Tanker moored to an offshore terminal. Full-scale ice abrasion of a marine transfer hose. Moored tanker in 10/10 pack ice. Photo courtesy of Alan C. McClure Associates, Inc. of Houston, Texas ICE ENGINEERING

6 HYDRODYNAMIC RESPONSES ONGOING INVESTIGATIONS OF A WAVE PIERCING BOW CONCEPT Head seas seakeeping test illustrates that the wave piercing bow stabilizes the hull in waves and prevents it from pitching and slamming. Naviform Consulting and Research Ltd. of Vancouver, BC, has completed the first part of Phase 3 of its research project 077, co-sponsored by the National Research Council - Industrial Research Assistance Program (NRC-IRAP), and American Bureau of Shipping. The project examines a wave piercing bow concept for a monohull. The ongoing research, which began in 2000, indicates that a significant reduction of motions and structural loads in a seaway can be achieved without any active ride control devices. It will result in greatly improved ride quality and reduced hull scantlings, making this type of hull very attractive for a number of commercial vessel applications. In order to validate these new design concepts and provide accurate powering information, a comprehensive series of model tests was conducted. The final version of the hull was tested in February 2007 with a 1:15 scale model at the West Coast ship model test facility of Oceanic Consulting Corporation s Ocean Engineering Centre (OEC), in Vancouver, BC. The model was then shipped to the Institute of Ocean Technology (IOT) facilities in St. John s, Newfoundland, for the final testing of hull pressures and seakeeping response, with the goal of removing this type of hull from restrictive High Speed Craft code requirements. TIME DOMAIN PREDICTION OF VIV Amplitude Ratio Time domain simulation of riser VIV. Oceanic Consulting Corporation, in conjunction with Memorial University of Newfoundland, is currently working on the development of a time-domain computer code for the prediction of Vortex Induced Vibration (VIV). This code makes full use of the lift, added mass, and drag coefficient curves derived from forced VIV experiments with relatively short segments of risers. Continuing on from Oceanic s DeepStar JIP work where forced and free VIV experiments were conducted, the algorithm has been used to successfully reconcile the two testing methods. During forced experiments where the cylinder amplitude of oscillation was continuously changing, the derived hydrodynamic coefficients for a single extracted cycle were similar to experiments where the oscillation was constant but at the same amplitude and frequency as that which occurred during a single cycle. This meant that the fluid had no memory, and hydrodynamic forces only depended on the present state (i.e., amplitude ratio and reduced velocity) of the cylinder in the flow. Initially, the algorithm was coded to test a simple single degree-offreedom oscillator with 1 parameters 0.9 corresponding to the DeepStar free VIV 0.8 experiments. The forcing 0.7 functions were derived 0.6 from corresponding force oscillation tests with the 0.5 same cylinder. The 0.4 algorithm works by 0.3 examining the previous 0.2 VIV cycle to determine the riser state variables; 0.1 then the threedimensional forced VIV 0 curves are interrogated to generate lift, added mass, Amplitude Ratio (A*) and drag coefficients. These are used in turn to force the cylinder during the next VIV cycle. Subsequently, the in-line degree-of-freedom was incorporated as a second independent oscillator, with a static and time varying drag force as the forcing function. Memorial University researcher Dr. Wei Qiu is currently incorporating these algorithms in a time-domain finite element analysis (FEA). The time-domain FEA will allow for time and spatially varying currents, large-scale phenomena which may lead to riser clashing, and can easily incorporate suppression devices if the corresponding empirical data is available Nominal Reduced Velocity (U*) Free VIV (T-D Simulation) Free VIV Experimental Comparison of numerical simulation with experimental data.

7 Tim Moore joined Oceanic Consulting Corporation in 2002 after completing a Bachelor of Applied Science in Engineering Physics at the University of British Columbia. Mr. Moore started his engineering career in 1996 with CESL Engineering where he was a project manager for the design, construction, and optimization/maintenance of research and development process equipment. As an engineer and project manager at Oceanic, Mr. Moore has brought leadership to numerous offshore and shipping projects, including model testing of the Red Hawk Cell Spar for the evaluation of VIM suppression strakes, and the assessment and analysis for the topsides PROFILE: TIM MOORE transportation and float-over installation of the Sakhalin Lunskoye field GBS. Since 2004, Mr. Moore has worked extensively with designers at Lockheed Martin Maritime Systems and Sensors, builders at Alaska Ship and Drydock, and the US Office of Naval Research, in the management of an extensive evaluation of the E-Craft Demonstrator (Sea- Lifter). This work included the design and development of new model instrumentation in addition to analysis procedures for assessing the vessel model in ice and wave conditions. Mr. Moore s extensive experience with SWATHs was advantageous in the investigation of resistance of a high-speed surface-effect ship for Textron Marine & Land Systems, and the evaluation of resistance and controllability of an Alan McClure SWATH design for NOAA, as well as the subsequent revised design for Halter Marine/NOAA. A sailor himself, Mr. Moore enjoys the evaluation of high-performance yachts. He was involved in the extensive hydrodynamic evaluation of hull designs for one of the 2007 America s Cup Syndicates along with the assessment of proposed modifications to the classic 12-meter Class yacht, KZ-7 (Kiwi Magic). He has also undertaken measurements of available force from full-scale fins used in an active roll suppression system for large yachts and boats. A leading research and development professional, Mr. Moore has conducted several internal projects including the design and testing of a truncated system to emulate a deepwater mooring for an FPSO in a relatively shallow model water depth; the development and implementation of several technologies for the measurement of dynamic pressure loads on model hulls, including the development and fabrication of in-house instruments; the development of an improved methodology for measuring wave profiles at high encounter frequencies; and the development of a methodology to create shear flow currents in a flume tank. Mr. Moore is a member of both the Society of Naval Architects and Marine Engineers (SNAME) and the Professional Engineers and Geoscientists of Newfoundland and Labrador (PEG-NL). PROFILE NEWS SMOOTH SAILING: OCEANIC REACHES NEW AGREEMENT WITH NRC Oceanic Consulting Corporation is pleased to announce that it has entered into a new multiyear agreement with the National Research Council of Canada to continue providing commercial services using NRC s facilities at the Institute for Ocean Technology in St. John s, Newfoundland. The renewable agreement provides Oceanic with facility access and scientific support to continue to build its international business in marine performance evaluation. The agreement is the second multiyear agreement reached between Oceanic and NRC. The first five year agreement, reached in 2002, was scheduled to terminate at the end of August of this year. This new accord allows Oceanic to continue to provide comprehensive consulting services using the world class suite of facilities based in St. John s IOT facilities and Memorial University. OCEANIC ASSUMES OPERATION OF TESTING FACILITY IN VANCOUVER, BC Oceanic Consulting Corporation is expanding its North American operations by assuming the operation of the Towing Tank and Wave Basin formerly operated by Vizon SciTech Inc. The West Coast is a dynamic and growing market with many design, shipping and shipbuilding companies based in the region; this acquisition will allow Oceanic to be closer to our West Coast clients and to provide better support for their needs. Oceanic's West Coast facility is a cost-effective alternative to larger tanks and offers a 67-meter Towing Tank, a 30-meter by 26-meter Wave Basin, and a shallow water Towing Tank. Oceanic is pleased to offer performance prediction services using these facilities, along with its established services and technologies resident on the East Coast, to all of its clients. This acquisition will also provide faster access to testing facilities and quicker project turnaround time for our clients. Over the past 25 years, the facility on the University of British Columbia campus has built a strong reputation among naval architects and ship builders throughout the Pacific Northwest as a facility of choice for ship design testing and research. Oceanic intends to maintain this reputation and to continue to offer its clients unique and costeffective manners of undertaking marine performance evaluations.

8 VIV Test Apparatus Specifications: Specifications: Cylinder Diameter m (12 schedule 40 aluminum pipe) Cylinder Coverings Smooth, various sand-grain roughness, strakes, fairings, fouled VIV suppression Cylinder Length 6.22 m (L/D=17), with end plates Cylinder Vertical Position 2.0 m below the free surface (approx. 7xD at centre) Maximum Reynolds Number 1.8 x 10 6 Dynamometer 20 kn in drag ± 10 kn in lift connected to a steel beam backbone Maximum Towing Speed 4 to 5 m/s depending on drag Turbulence Generation 6% and 10% turbulence stimulation screens can be fitted Primary Data Products Cylinder loads, displacements, velocities and accelerations Forced Vibration Mode: Amplitude Ratio Up to 1.1 Frequency Range From 0.3 to 1.2 Hz Drive Motor for Forced 36 kw hydraulic servomotor drives struts attached to test Vibration cylinder Derived Output 3-D surface plots of lift (C LV ), drag (C D ) and added mass coefficients (C M ) as functions of amplitude ratio (A*) and reduced velocity (V R ) Motion profiles Sinusoidal, monochromatic and bichromatic (beating) Free Vibration Mode : Amplitude Ratio Up to 1.0 System Tuning System natural frequency can be tuned via changes to springs (10 kn/m to 160 kn/m). Generally 0.5 to 1.5 Hz. System Damping Variable via a 3 kw servomotor that can feed energy into the system Two Degrees-of-Freedom In-line motion can be free or locked. If free, then natural frequency can be varied by altering spring stiffness Mass Ratio (m*) Typically 1.5 Derived Output Generic A* versus U* plot, at C LV =0, correlation data, cylinder motion in two degrees-of-freedom Specification Sheets are Available for All Major Facilities, Including: Offshore Engineering Basin 200-meter Wave/Towing Tank 58-meter Wave/Towing Tank 90-meter Ice/Towing Tank Cavitation Tunnel 22-meter Flume Tank Centre for Marine Simulation VIV Test Apparatus MOTSIM Specification sheets can be obtained from the Oceanic website or by contacting our office. Meet us at: 95 Bonaventure Ave., Suite 401 St. John s, NL Canada A1B 2X5 Telephone Facsimile oceanic@oceaniccorp.com April 30-May 3 Houston, TX May Stamford, CT October Fort Lauderdale, FL November Fort Lauderdale, FL November New Orleans, LA ISO