Optimization of NACA 4412 augmented with a gurney flap by using grey relational analysis

The gurney flap which has increased the lift coefficient at the trailing edge is used to improve the aerodynamic performance of the airfoil. In this study, the effect of the aerodynamic performance of baseline augmented with various dimensions of gurney flap (GF) structures was optimized by Taguchi method-based grey relational analysis (GRA) unlike previous works. Based on Taguchi's L-16 orthogonal array method, the designs of the experiments were employed to optimize four control factors that were position (Delta x), angle (alpha), thickness (Delta t), and length (Delta L) of the GF on the airfoils. In aerodynamic studies based on GRA method, optimum parameters for alpha, Delta L, Delta t, and Delta x of GF were obtained as 75 degrees, 1.5%c, 2%c, and 0%c. The degree of effect in aerodynamic performance was investigated by analysis of variance (ANOVA). The results show that the effect order of these four control factors was obtained as Delta x > Delta h > Delta t > alpha which means that while Delta x parameter with 37.62% has the strongest effect on the lift coefficient (C-L) and drag coefficient (C-D), alpha parameter with 3.06% has the lowest effect. The use of the GF model, which has the most optimal parameter, increased the efficiency (high C-L; low C-D) by 35.62% compared to the baseline in terms of GRA. In addition, empirical equations of the C-L and C-D on the airfoils were derived by regression analysis (RA). The values attained from empirical and numerical results (confirmation test) were highly compatible with each other.