Numerical Analysis of Effects of Arms with Different Cross-Sections on Straight-Bladed Vertical Axis Wind Turbine

Abstract

Most vertical axis wind turbines (VAWTs) need arms connecting the blades with the rotational axis. The arms increase the power loss of VAWTs; however, the distribution between the pressure and friction influences and their degrees of influence have not yet been investigated in detail in past research. We applied computational fluid dynamics (CFD) targeting a small-sized straight-bladed VAWT to elucidate the effects of arms on turbine performance. In the analysis, three kinds of arms with different cross-sections (NACA 0018 airfoil, 18% rectangular, circular) with the same height were added to an armless rotor. The tangential forces and resistance torques caused by the added arms were recalculated by dividing the pressure and friction influences based on the surface pressure and friction distributions obtained by the CFD on an arm or a blade. The pressure-based tangential force of an arm, regardless of the cross-section, had a tendency to increase near the connection part between the arm and a blade. Though the value was small, the friction on the rectangular arm generated a driving force, whereas the friction on the other arms generated resistance forces. The pressure-based tangential force of a blade increased for a wide region around the connection part. The friction-based tangential force of a blade dropped around the connection part of every arm-equipped rotor. The arm resistance torque added to a VAWT by the existence of arms was larger than the added blade resistance torque in the cases of rectangular and circular arm rotors. Conversely, in the case of the airfoil arm rotor, the resistance torque added to blades became larger than that of arms.

Investigating of Flow Field and Power Performance on a Straight-blade Vertical Axis Wind Turbine with CFD Simulation

“…This same conclusion is approached in reference [15]. Hara Y et al studied the influence of arms of different sections on the VAWT and found that the drag torque of the rotor of the airfoil arm added to the blade became larger than that of other arms [16].…”

Aerodynamic Shape Optimization of a NACA0018 Airfoil Using Adjoint Method and Gradient-Based Optimizer

“…Many studies have been done on the VAWT to optimize or maximize its performance way by suggesting and comparing various different types of turbine blades. Comparisons between support arm geometries such as implementing symmetrical NACA blades [5,6] or variations of it [7,8] as well as other shapes [9,10] which generally tends to favour airfoils shapes when it comes to power efficiency losses. However, implementation of shape optimization techniques to generate a novel blade design for VAWT use has recently seen a rise in interest.…”

Wind tunnel experimental study on static aerodynamic performance of SB-VAWT without intermediate support axes

“…Benjamin Strom et al (Strom et al, 2018) introduced the analytical models for the power loss due to mounting structure drag and examined the interactions between turbine blades and mounting structures. Yutaka Hara et al (Hara et al, 2019) attached three types of support arms with different cross-sectional shapes to a small SB-VAWT rotor without support arms. The surface pressure and friction distribution on the blades and support arms were analyzed using CFD.…”