Performance Analysis of a Vertical Axis Tidal Turbine With Flexible Blades

In this study, a vertical axis tidal turbine with flexible blades is investigated. The focus is on analyzing the effect of flexible airfoils types and blade flexibility on turbine net output power. To this end, five different flexible airfoils （Symmetric and Non-symmetric） are employed. The results show that the use of a thick flexible symmetric airfoil can effectively increase output power compared to that achievable with a conventional rigid blade. Moreover, the use of highly flexible blades, as opposed to less flexible or rigid blades, is not recommended.

Three-dimensional numerical simulation of a vertical axis tidal turbine using the two-way fluid structure interaction approach

The objective of this study was to develop, as well as validate the strongly coupled method (two-way fluid structural interaction (FSI)) used to simulate the transient FSI response of the vertical axis tidal turbine (VATT) rotor, subjected to spatially varying inflow. Moreover, this study examined strategies on improving techniques used for mesh deformation that account for large displacement or deformation calculations. The blade's deformation for each new time step is considered in transient two-way FSI analysis, to make the design more reliable. Usually this is not considered in routine one-way FSI simulations. A rotor with four blades and 4-m diameter was modeled and numerically analyzed. We observed that two-way FSI, utilizing the strongly coupled method, was impossible for a complex model; and thereby using ANSYS-CFX and ANSYS-MECHANICAL in work bench, as given in ANSYS-WORKBENCH, helped case examples 22 and 23, by giving an error when the solution was run. To make the method possible and reduce the computational power, a novel technique was used to transfer the file in ANSYS-APDL to obtain the solution and results. Consequently, the results indicating a two-way transient FSI analysis is a time- and resource-consuming job, but with our proposed technique we can reduce the computational time. The ANSYS STRUCTURAL results also uncover that stresses and deformations have higher values for two-way FSI as compared to one-way FSI. Similarly, fluid flow CFX results for two-way FSI are closer to experimental results as compared to one-way simulation results. Additionally, this study shows that, using the proposed method we can perform coupled simulation with simple multi-node PCs (core i5).

Numerical and Experimental Study of the 3D Effect on Connecting Arm of Vertical Axis Tidal Current Turbine

Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF（User Defined Function） command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.