Development of a New Federally Funded Wind/Wave/Towing Basin to Support the Offshore Renewable Energy Industry

This paper presents technical details for a unique newly constructed model testing facility for offshore renewable energy devices and other structures established through federal and state funding. The University of Maine (UMaine) has been an active contributor to research in the field of floating offshore wind turbine (FOWT) design and scale-model testing for the past 6 years. Due to a lack of appropriate test facilities in the United States, UMaine has led multiple 1:50 scale-model tests of FOWT platforms internationally, leading to the motivation to design and build a state-of-the-art test facility at UMaine which includes high-quality wind generation with waves and towing capabilities. In November of 2015, UMaine opened the Alfond Wind/Wave Ocean Engineering Laboratory (W2) at the Advanced Structures and Composites Center. This facility, shown in Figure 1, contains a 30m long x 9m wide x 0-4.5m variable floor depth test basin with a 16-paddle wave maker at one end and a parabolic wave attenuating beach at the other. This basin is unique in that it integrates a rotatable open-jet wind tunnel over the basin that is capable of simulating high-quality wind fields in excess of 10 m/s over a large test area. Since opening, the W2 has provided testing for various scale-model FOWT designs, oil and gas vessels such as a scale-model floating production storage and offloading (FPSO) vessel, and a large number of wave energy conversion (WEC) devices in support of the Department of Energy’s (DOE) Wave Energy Prize. In addition to scalemodel testing, the W2 facility supports a wide range of model construction equipment including a 2.0m x 4.0m x 0.1m tall 3D CNC waterjet, a 3m long x 1.5m wide x 1.4m tall 5-axis CNC router, and an additive manufacturing facility housing a 0.6m x 0.6m x 0.9m 3D printer. To expand the capability of W2, a towing system is currently being designed to operate in conjunction with the multi-directional wave maker, which is shown in Figure 5. This equipment will provide bi-directional towing for a variety of applications. In addition to standard resistance testing, the broad aspect ratio of the basin provides reduced blockage effects while the multi-directional wave maker allows for tow testing a large number of wave environments and headings. The moving floor enables intermediate to shallow water tow tank tests, which are important for capturing the wave kinematics applicable to coastal environments, while the relatively deep water depths support testing of large structures such as tidal turbines and tow-out operations for THE 30th AMERICAN TOWING TANK CONFERENCE WEST BETHESDA, MARYLAND, OCTOBER 2017 2 large offshore structures such as wind and wave floating energy platforms. To test the capabilities of this system, UMaine is constructing a 1:50-scale model of the David Taylor Model Basin (DTMB) 5415 to perform commissioning tests. The towing system is planned to be operational in 2018.