Powering the blue economy through offshore vertical-axis wind and current turbines; from fundamental to two-phase flow experimental testing

Within the past few years an increased interest has been shown regarding marine renewable energy and its applications.The overall goal of this project was to develop and test an economically and technically feasible offshore platform to house a vertical axis wind turbine and an underwater current turbine, known as dual turbine platform (DTP), that can provide sustainable and ecofriendly energy, relieving the operation of diesel generators for aquaculture farms.In an offshore DTP design, the wind interacts with the unsubmerged parts of the floating platform, wind turbine blades, hub, and tower, while the current and waves interact with the portion of the system that is submerged, i.e., mooring lines, current turbine, and submerged portion of the platform.This interaction between the fluid flow and the floating structure is known as Fluid-Structure Interaction (FSI), that can lead to excessive dynamic loads on the system and potentially could lead to instability and failure of the DTP.To commercially implement floating offshore platforms, it is critical that the platform remains stable in varying environmental and operational conditions.To study the offshore wind turbine's stability and energy output over a range of wind speeds and currents, there is an unmet need to have a testing facility capable of simulating a two-phase flow to mimic various ocean current and wind situations, simultaneously.On this basis, the first objective in the current study was to design and manufacture a small-scale wind tunnel that could be integrated into the existing recirculating water tunnel at the Fluid-Structure Interactions Laboratory at UMass Dartmouth, providing a two-phase flow testing facility, i.e., wind and water.With the small-scale test section of the flow channels, the second objective in the current study was to study the FSI response and stability of a DTP over a wide range of wind and current conditions.Accurate construction of the platform prototype and scaling of the surrounding conditions was achieved by using Froude Scaling and Actuator Disk Theory.Our in-house designed and manufactured two-phase flow channel facilitated our experimental stability study of the floating DTP over a wide range of wind and current conditions.