Ling Wan

Model Test of the STC Concept in Survival Modes

The STC (Spar Torus Combination) concept combines a Spar floating wind turbine and a torus-shaped heaving-body wave energy converter (WEC). Numerical simulation has shown positive synergy between the WEC and the Spar floating wind turbine in operational conditions. However, in extreme wind and wave conditions, it is challenging to maintain structural integrity, especially for the WEC. To ensure survivability of this concept in extreme conditions, three survival modes have been proposed.To investigate the performance of the STC in extreme conditions, model tests with a scale factor of 1:50 were carried out in the towing tank of MARINTEK, Norway. Two survival modes were tested. In both modes, the Torus WEC was fixed to the Spar. In the first mode, the Torus WEC is at the mean water surface, while in the second mode, the Torus WEC is fully submerged to a specified position. In the tests, 6 D.O.F rigid body motions, mooring line tensions, forces in 3 directions (X, Y and Z) between the Spar and Torus were measured, wind velocity and wind force were also measured by a sensor in front of the model and a load cell installed on the wind disc.In this paper, the model test set-up for the two survival modes are described, and then decay tests, regular wave tests and the statistical tests for wind only, irregular wave only and irregular wave plus wind are presented, compared and analyzed. In the mean water level survival mode, the Torus had a small draft and large water plane area, so slamming and green water were observed as expected. In addition, Mathieu instability phenomena were observed during the regular wave test. In some large wave conditions in the fully submerged mode, no severe wave load occurred. All the results are presented in model scale unless specified, for direct comparison with numerical simulations later.Copyright

Initial Design of a Double Curved Floating Bridge and Global Hydrodynamic Responses Under Environmental Conditions

In this paper, a floating bridge concept is proposed. This bridge concept comprises a two oppositely curves in plan, which enables the cancellation of the axial forces at the bridge as one arch will be under compression while the other arch is in tension due to environmental forces acting in one direction. The road deck is carried by truss structures that are kept above the water by several elliptical cylindrical pontoons. To reduce drag load, the cross sectional area facing the current is reduced as much as possible, while the buoyancy is kept the same based on the initial weight estimation. Initial design consideration and methodology of a double curved floating bridge is presented, and a numerical model is established for analyzing this concept. Hydrodynamic and structural dynamic aspects are included in the numerical model. Parametric study of the bridge structural rigidity is performed to investigate the effect to the responses. White noise, regular and irregular wave simulations are carried out to investigate the dynamic responses of the floating bridge under different conditions.

A Hydrodynamic Analysis of Motion Coupling Effect of Floating Storage Tank Supported by Marine Fenders

This study concerns a new concept of floating oil storage facility, to be deployed in coastal waters, in which separate oil storage tanks float in an array, separated by a mooring fender system. In this paper, hydrodynamic properties of a single module are investigated numerically. The effects of different mooring fender parameters including fender stiffness and fender position on the coupled motions are studied. Design criteria and a design approach for the marine fender selection are proposed. Next, time-domain simulations under random waves are performed. Finite water depth effects are taken into consideration. Then a brief parametric study on sloshing phenomenon in fendersupported tanks is conducted. Results show that a carefully designed marine fender will help reduce the roll and pitch motions of the storage tank, and thus function as a stabilizer. This analysis is the basis of a global hydrodynamic response analysis for multiple tanks, including the effects of multibody hydrodynamic interactions between tanks in the future.