Modelling and simulation of flow induced vibrations in vertical axis wind turbine blade

Abstract

The interaction between fluids and structures play an important role in number of fields. Important applications can be found in wind turbine blades, airplane wings, tall buildings, suspension bridges and biomechanics. The flow induced vibration (FIV) may affect negatively the operation and the response of the system. Flow induced vibrations in wind turbine blades is one of main considerations for the design of wind turbine, because aerodynamic loading causes blade to bend mostly in flap wise direction, and causes blade section to twist to create new fluid fields surrounding the blade. This interaction between aerodynamics and deformation of wind turbine blade may lead to flow induced vibrations. The aim of this research is to analyze the problem of FIV in wind turbine blade, due to the pressure field caused by a fluid flow. For this purpose, vertical axis wind turbine is analyzed using computational fluid dynamics and finite element analysis for the computation of vibratory stresses. Three dimensional flow analysis of vertical axis wind turbine (VAWT) blade is performed at different TSR ranges from 2.5 to 4.5. The aerodynamics results of CFD analysis shows that the maximum torque of 75 Nm is obtained at TSR 3.5. Finite element analysis (FEA) is then used for the computation of vibratory stresses. Carbon epoxy composite material with orthotropic properties is used as the blade material for FEA analysis. First one-way Fluid Structure Interaction (FSI) is conducted to determine stress field due to the torque on wind turbine blade. Next Modal analysis is performed to obtain the natural frequencies and corresponding mode shapes. Finally, the force response analysis of the structure is performed using ANSYS transient structural module under maximum unsteady wind torques which were computed using ANSYS Fluent. The outcome of the analysis showed that the three bending modes are the most critical modes for blade failure.