Effect of Reynolds Number on Aerodynamics of Airfoil with Gurney Flap

Shubham Jain,Nekkanti Sitaram,Sriram Krishnaswamy

doi:10.1155/2015/628632

Abstract

Steady state, two-dimensional computational investigations performed on NACA 0012 airfoil to analyze the effect of variation in Reynolds number on the aerodynamics of the airfoil without and with a Gurney flap of height of 3% chord are presented in this paper. RANS based one-equation Spalart-Allmaras model is used for the computations. Both lift and drag coefficients increase with Gurney flap compared to those without Gurney flap at all Reynolds numbers at all angles of attack. The zero lift angle of attack seems to become more negative as Reynolds number increases due to effective increase of the airfoil camber. However the stall angle of attack decreased by 2° for the airfoil with Gurney flap. Lift coefficient decreases rapidly and drag coefficient increases rapidly when Reynolds number is decreased below critical range. This occurs due to change in flow pattern near Gurney flap at low Reynolds numbers.

Highlights

A Gurney flap (GF) is a microtab fitted perpendicular to the airfoil near the trailing edge on its pressure surface which increases the lift by altering the Kutta condition and increasing effective camber
Considerable efforts are carried out to study the effects of Gurney flap on the airfoil aerodynamics [2,3,4]
ANSYS FLUENT commercial Computational fluid dynamics (CFD) code with one-equation Spalart-Allmaras turbulence model is used for the six Reynolds numbers varying from 3.0 × 105 to 3.0 × 104

Summary

Introduction

A Gurney flap (GF) is a microtab fitted perpendicular to the airfoil near the trailing edge on its pressure surface which increases the lift by altering the Kutta condition and increasing effective camber. They are extensively used on helicopter stabilizers [1]. Mueller and Batill [5], Selig et al [6], Brown and Filippone [7], and Traub and Agarwal [8] have studied the performance of airfoils at low Reynolds numbers but a systematic investigation is still not available. For smaller UAVs and MAVs, airfoil chord and velocity of aircraft are lower; they operate at low Reynolds numbers. Gurney flaps are used in turbomachinery to improve their performance at low Reynolds number due to their inexpensive method of lift enhancement [11]

Methods

Results

Conclusion