Numerical and experimental investigation of wind loadings on vertical axis wind turbine blade deflection

Abstract

This work focuses on experimental and numerical investigation of the deflection on VAWT blade surface against the high measured wind speeds that were simulated in FLUENT to obtain the corresponding static forces. The effect of forces, blade setting angle and thickness to chord ratio along with their combined effects on deflection were assessed experimentally and numerically. Three airfoils of gradually increasing thickness to chord ratio, NACA 0015, 0021 and 4412, were selected along with three levels of forces and tested at 5°, 10° and 15° of blade setting angle. A 33 factorial experimental design was used to perform experiments and Analysis of variance (ANOVA) confirmed that individual effects of force and thickness to chord ratio were the most significant factors while blade setting angle had lesser significance on deflected values. However, interactive effects of these parameters were significant. Minimum deflections were observed in the range of 0.25-0.28 mm on NACA 0021 at 3 kg force in combination with all blade setting angles. Maximum observed value of defection was 1 mm, which occurred at 9 kg force at 5°, 10° and 15° of blade setting angle on NACA 0015 and 4412 airfoil shapes. The results ensure that the blade structure remains stable at 9 kg which corresponds to 20 m/s wind speed without affecting the performance. The deflections obtained from Finite element method were compared with experimental results and found in good agreement with each other.