Abstract
To explore the effect of the height of vortex generators (VGs) on the control effect of boundary-layer flow, the vortex characteristics of a plate and the aerodynamic characteristics of an airfoil for VGs were studied by both wind tunnel experiments and numerical methods. Firstly, the ratio of VG height (H) to boundary layer thickness (δ) was studied on a flat plate boundary layer; the values of H are 0.1δ, 0.2δ, 0.5δ, 1.0δ, 1.5δ, and 2.0δ. Results show that the concentrated vortex intensity and VG height present a logarithmic relationship, and vortex intensity is proportional to the average kinetic energy of the fluid in the height range of the VG. Secondly, the effects of height on the aerodynamic performance of airfoils were studied in a wind tunnel using three VGs with H = 0.66δ, 1.0δ, and 1.33δ. The stall angle of the airfoil with and without VGs is 18° and 8°, respectively, so the VGs increase the stall angle by 10°. The maximum lift coefficient of the airfoil with VGs increases by 48.7% compared with the airfoil without VGs, and the drag coefficient of the airfoil with VGs is 84.9% lower than that of the airfoil without VGs at an angle of attack of 18°. The maximum lift–drag ratio of the airfoil with VGs is lower than that of the airfoil without VGs, so the VGs do not affect the maximum lift–drag ratio of the airfoil. However, a VG does increase the angle of attack of the best lift–drag ratio.
Highlights
According to the latest data from the Global Wind Energy Council [1], as of 2017, the total installed capacity of the global wind power market has reached 539.6 GW, and wind power has become the third largest power source in the world
vortex generators (VGs) the leeward surface, forming a concentrated vortex on the leeward side, and the intensity of the vortex to the leeward surface, forming a concentrated vortex on the leeward side, and the intensity of the reachesreaches the maximum at the trailing of the is a logarithmic relationshiprelationship between the vortex the maximum at the edge trailing edge of There the VGs
There is a logarithmic between the vortex circulation and VG height, and the average kinetic energy of the fluid in the boundary layer has a logarithmic relationship with the VG height, so the vortex intensity of the
Summary
According to the latest data from the Global Wind Energy Council [1], as of 2017, the total installed capacity of the global wind power market has reached 539.6 GW, and wind power has become the third largest power source in the world. Many novel methods have been proposed for improving the performance of wind turbine blades in recent years, such as vortex generators (VGs) [7], microflaps [8], microtabs [4], blowing and suction [9], synthetic jets [10], flexible wall [11], and plasma actuators [12]. As reported by Lin [7] and Wang [15], vortex generators are among the most effective devices for improving the aerodynamic performance of blades. Taylor [16] introduced vortex generators in 1947, and they were originally implemented in the field of flow control for aircraft wings. Under the action of the Energies 2019, 12, 959; doi:10.3390/en12050959 www.mdpi.com/journal/energies
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