Fluid Structure Interaction Modelling of Tidal Turbine Performance and Structural Loads in a Velocity Shear Environment

Abstract

Tidal Current Turbine (TCT) blades are highly flexible and undergo considerable deflection due to fluid interactions. Unlike Computational Fluid Dynamic (CFD) models Fluid Structure Interaction (FSI) models are able to model this hydroelastic behavior. In this work a coupled modular FSI approach was adopted to develop an FSI model for the performance evaluation and structural load characterization of a TCT under uniform and profiled flow. Results indicate that for a uniform flow case the FSI model predicted the turbine power coefficient C P with an error of 4.8% when compared with experimental data. For the rigid blade Reynolds Averaged Navier Stokes (RANS) CFD model this error was 9.8%. The turbine blades were subjected to uniform stress and deformation during the rotation of the turbine in a uniform flow. However, for a profiled flow the stress and deformation at the turbine blades varied with the angular position of turbine blade, resulting in a 22.1% variation in stress during a rotation cycle. This variation in stress is quite significant and can have serious implications for the fatigue life of turbine blades.

Two-Way Fluid–Solid Interaction Analysis for a Horizontal Axis Marine Current Turbine with LES

“…Bahaj et al considered the influence of the support on MCT performance and placed it as far as at least one rotor radius downstream of the rotor. The variation would be larger a velocity profile of 1/7th power law was used instead of uniform velocity [22].…”

“…Also, it is beneficial to consider the interaction between the structure and the flow field in evaluating the performance and the details of the structure response of MCTs. Badshah et al [22] compared the one-way and two-way FSI method applied to an MCT modeled as a structural-steel solid. The maximum blade displacement was only 1/2000 of its radius.…”

Coupled Fluid-Structure Interaction Modelling of Loads Variation and Fatigue Life of a Full-Scale Tidal Turbine under the Effect of Velocity Profile

“…While velocity profiles vary considerably from site to site depending on the local bathymetric conditions, these velocity profiles can typically be approximated using power laws. The 1/7th and 1/10th power laws have been used to estimate the velocity profiles for EPRI North American tidal in stream power feasibility demonstration project [40] and other previous research works [14,38]. The flow is assumed to only vary along the depth, and stays uniform across the width of the domain.…”

“…However, the focus of the study was solely on the hydrodynamic performance of the turbine under the effect of wave-current interaction. We developed a similar full 3D FSI analysis methodology requiring a shorter computational time for a small scale tidal turbine rotor [38]. While our study reported the load variation during a rotation cycle, the turbine design was a scale model, the support structure/tower was not included, and the blade design was simplified.…”

“…In this paper, we extend our earlier developed [38] coupled FSI analysis procedure to evaluate the effects of velocity profile on the structural loads encountered by rotating tidal turbine blades. To accomplish this, we used a more realistic full-scale complete twin bladed turbine design with hub, nacelle and support tower.…”