Numerical study of effect of solidity on vertical axis wind turbine with Gurney flap

Gurney flap is a miniature lift-enhancement device installed at the airfoil trailing edge and has been successfully applied to fixed wing aircraft and low-speed horizontal wind turbines. In this ar...

https://journals.sagepub.com/doi/pdf/10.1177/1687814018803804

Experimental and numerical study on the performance of an axial fan with a Gurney flap

For a variable-pitch axial fan with guide vanes, the effect of three series of Gurney flaps (GFs) configured at the trailing edge of blades on the performance and dynamics is numerically investigat...

Effect of Gurney Flap on Performance and Aeroacoustics of Variable-Pitch Axial Fans

Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gurney flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 m/s. The chord length (C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76×105. Gurney flaps with the heights ranging from 0.25%C to 3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack (3°), Gurney flap with the height of 0.5%C can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gurney flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gurney flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack (≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition.

Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil

In this paper, the numerical simulation was used to investigate the effects of the leading-edge slat installation angles (β for airfoils from 0° to 40° and β1 for blades from −20° to 40°) on the ae...

Investigation of leading-edge slat on aerodynamic performance of wind turbine blade:

Numerical simulation of Gurney flap on SFYT15thick airfoil

Regularities between kinematic and aerodynamic characteristics of flexible membrane wing

Abstract Piezoelectric macro-fibre composite (MFC) actuators are employed onto the flexible leeward surface of an airfoil for active control. Time-resolved aerodynamic forces, membrane deformations and flow fields are synchronously measured at low Reynolds number (Re = 6 × 104). Mean aerodynamics show that the actively controlled airfoil can achieve lift-enhancement and drag-reduction simultaneously in the angle of attack range of 10° ≤ α ≤ 14°, where the rigid airfoil encounters stall. The maximum increments of lift and lift-to-drag ratio are 27.1 % and 126 % at the reduced actuation frequency of ${f^ + } = 3.52$. The unsteady coupling features are further analysed at α = 12°, where the maximum lift-enhancement occurs. It is newly discovered that the membrane vibrations and flow fields are locked into half of the actuation frequency when ${f^ + } > 3$. The shift of the dominant vibration mode from bending to inclining is the reason for the novel ‘half-frequency lock-in’ phenomenon. To the fluid–structure interaction, there are three characteristic frequencies for the actively controlled airfoil: $S{t_1} = 0.5{f^ + }$, $S{t_2} = {f^ + }$, and $S{t_3} = 1.5{f^ + }$. Here, St1 and its harmonics (St2, St3) are coupled with the natural frequencies of the leading-edge shear layer, resulting in the generation of multi-scale flow structures and suppression of flow separation. The lift presents comparable dominant frequencies between St1 and St3, which means the instantaneous lift is determined by the flow structures of St1 and St3. The local membrane bulge and dent affect the instantaneous swirl strength of flow structures near the maximum vibration amplitude location, which is the main reason for the variation of instantaneous lift.

Xi He

Papers

Numerical simulation of Gurney flap on SFYT15thick airfoil

Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil

Regularities between kinematic and aerodynamic characteristics of flexible membrane wing

Aerodynamics and fluid–structure interaction of an airfoil with actively controlled flexible leeward surface

Incomplete fluid–structure coupling mechanism of a flexible membrane wing