Abstract
Aerodynamic performance improvement of wind turbine blade is the key process to improve wind turbine performance in electricity generated and energy conversion in renewable energy sources concept. The flow behavior on wind turbine blades profile and the relevant phenomena like stall can be improved by some modifications. In the present paper, Humpback Whales flippers leading edge protuberances model as a novel passive stall control method was investigated on S809 as a thick airfoil. The airfoil was numerically analyzed by CFD method in Reynolds number of 106and aerodynamic coefficients in static angle of attacks were validated with the experimental data reported by Somers in NREL. Therefore, computational results for modified airfoil with sinusoidal wavy leading edge were presented. The results revealed that, at low angles of attacks before the stall region, lift coefficient decreases slightly rather than baseline model. However, the modified airfoil has a smooth stall trend while baseline airfoil lift coefficient decreases sharply due to the separation which occurred on suction side. According to the flow physics over the airfoils, leading edge bumps act as vortex generator so vortices containing high level of momentum make the flow remain attached to the surface of the airfoil at high angle of attack and prevent it from having a deep stall.
Highlights
Sustainable energy resources are becoming an increasing source of energy and developed rapidly
Since large horizontal-axis wind turbines are very expensive and operate for many years after the initial installation, it is important to design the wind turbine rotor blades in an aerodynamically efficient manner such that the maximum possible energy conversion can be achieved for the initial investment cost [1]
All the stall control mechanisms try to keep boundary layer attached to the surface of the airfoil to prevent separation which leads to decreasing aerodynamic performance and energy conversion efficiency
Summary
Sustainable energy resources are becoming an increasing source of energy and developed rapidly. Kang and Park [11] investigated an active stall control of wind turbine airfoil method using a continuous jet to improve the aerodynamic characteristics. All the stall control mechanisms try to keep boundary layer attached to the surface of the airfoil to prevent separation which leads to decreasing aerodynamic performance and energy conversion efficiency. Johari et al [13] investigated drag, lift, and pitching moments of NACA 634-021 experimentally and showed that, for the airfoil with sinusoidal leading edge protuberances in angle of attacks higher than baseline airfoil stall, lift coefficient improves significantly with no penalty in drag coefficient. Static performance investigation was compared to experimental results and the effects of leading edge bump were considered in S809 during pre- and poststall regime of angles of attack
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