Comparative Study of Dynamic Stall between an Aircraft Airfoil and a Wind Turbine Airfoil in an Air–Particle Flow

Junjun Jin,Di Zhou,Qiaozhong Li,Zhiliang Lu ,T.f Guo

doi:10.3390/app112210920

Abstract

Dynamic stall in clean air flow has been well studied, but its exploration in air–particle (air–raindrop or air–sand) flow is still lacking. The aerodynamic performance loss of aircraft (NACA0012) and wind turbine (S809) airfoils and their differences during the hysteresis loop at different pitching parameters are also poorly understood. As shown in this paper, the reduced frequency has little effect on the value of the maximum lift coefficient increment caused by particles, but a larger one can enhance the hysteresis effect and drag the angle of attack, at which the maximum increment is obtained, from the up stroke to the down stroke. The large lift coefficient increments of two airfoils and their difference also have a similar change trend with the reduced frequency. Compared to that of NACA0012 airfoil, the increments of S809 airfoil are obviously greater at three mean angles of attack, especially at 8°, which is the commonly used operating angle. In addition, the angle of attack, at which the maximum lift coefficient is obtained, can be significantly changed by particles in two regions: one is under the effect of deep stall, the other is under the effect of light stall at a low, reduced frequency.

Highlights

Dynamic stall, caused by the continuous change of the angle of attack, has a significant effect on aerodynamic performance
For NACA0012 airfoil, the lift coefficient has a linear change with the angle of attack in the steady case, and the values during the up stroke are approximate to those during the down stroke in every pitching case
This paper shows the comparison of relative increment loops of the lift coefficient caused by particles between an aircraft airfoil (NACA0012) and a wind turbine airfoil (S809) at different reduced frequencies

Summary

Introduction

Dynamic stall, caused by the continuous change of the angle of attack, has a significant effect on aerodynamic performance. Larsen et al [21] developed a model for aerodynamic lift of wind turbine profiles, based on a backbone curve, in the form of the static lift, as a function of the angle of attack It combines memory delay effects under attached flow with reduced lift, due to flow separation under dynamic stall conditions. The associated exploration in a gas–solid flow is seriously lacking because of the small effect on the aerodynamic performance of an aircraft He [33] studied the effect of sand particles on the dynamic stall characteristics of NACA0012 airfoil at different particle diameters and concentrations. Where Dp is the particle diameter and CD,p is the particle drag coefficient, estimated by using the spherical drag law of Morsi and Alexander [39]

Numerical Validation

Hysteresis Loops at Different Reduced Frequencies

Conclusions