Effect of Single-Row and Double-Row Passive Vortex Generators on the Deep Dynamic Stall of a Wind Turbine Airfoil

Chengyong Zhu,Tongguang Wang,Wei Zhong,Jie Chen

doi:10.3390/en13102535

Chengyong Zhu, Tongguang Wang + Show 2 more

Open Access

https://doi.org/10.3390/en13102535

Copy DOI

Journal: Energies	Publication Date: May 16, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: Nanjing University of Aeronautics and Astronautics

Abstract

Passive vortex generators (VGs) have been widely applied on wind turbines to boost the aerodynamic performance. Although VGs can delay the onset of static stall, the effect of VGs on dynamic stall is still incompletely understood. Therefore, this paper aims at investigating the deep dynamic stall of NREL S809 airfoil controlled by single-row and double-row VGs. The URANS method with VGs fully resolved is used to simulate the unsteady airfoil flow. Firstly, both single-row and double-row VGs effectively suppress the flow separation and reduce the fluctuations in aerodynamic forces when the airfoil pitches up. The maximum lift coefficient is therefore increased beyond 40%, and the onset of deep dynamic stall is also delayed. This suggests that deep dynamic-stall behaviors can be properly controlled by VGs. Secondly, there is a great difference in aerodynamic performance between single-row and double-row VGs when the airfoil pitches down. Single-row VGs severely reduce the aerodynamic pitch damping by 64%, thereby undermining the torsional aeroelastic stability of airfoil. Double-row VGs quickly restore the decreased aerodynamic efficiency near the maximum angle of attack, and also significantly accelerate the flow reattachment. The second-row VGs can help the near-wall flow to withstand the adverse pressure gradient and then suppress the trailing-edge flow separation, particularly during the downstroke process. Generally, double-row VGs are better than single-row VGs concerning controlling deep dynamic stall. This work also gives a performance assessment of VGs in controlling the highly unsteady aerodynamic forces of a wind turbine airfoil.

Highlights

Passive vortex generators (VGs) are very simple, they have been proven to suppress the flow separation effectively and boost the aerodynamic performance of horizontal axis wind turbines (HAWTs) [1]
VGs significantly delayed the onset of dynamic stall
Single-row VGs bring about a vast decrease in the Cl from 2.2 to 0.3 near the αmax when the airfoil begins to pitch down, implying dynamic-stall behaviors

Summary

Introduction

Passive vortex generators (VGs) are very simple, they have been proven to suppress the flow separation effectively and boost the aerodynamic performance of horizontal axis wind turbines (HAWTs) [1]. Conventional VGs are composed of some pairs of vanes sticking out from the surface, angled to the incoming flow [2]. The height of VGs is close to the boundary-layer thickness. The fundamental principle of VGs is to produce streamwise vortices. These vortices can reenergize the boundary layer to resist the adverse pressure gradient. The effectiveness of VG designs is primarily determined by the evolution of streamwise vortices

Objectives

Results

Discussion

Conclusion