Numerical Simulations of Tandem-Airfoil Aerodynamics

Analysis of tandem wing aircraft configurations has been of interest to the aerospace community since the early 1970's. The theoretical performance gains from the use of two similarly-sized wings make this unusual configuration an enticing option for future aircraft designs. In this investigation, a two-dimensional Navier-Stokes analysis previously developed for internal flow geometries has been extended to external flow geometries. The modified flow analysis was validated against two sets of experimental data. A series numerical simulations were then performed for a tandem-airfoil configuration in which the stagger (chord-wise distance between the mid-chord of each airfoil) was varied. At each stagger position, the aerodynamic flow field was investigated at several negative and positive incidence angles. The predicted results indicate that (for moderate-to-large stagger distances) the aft airfoil performs similar to the fore airfoil at lower angles of attack. At higher angles of attack the lift-to-drag ratio of the fore airfoil is much greater than that of the aft airfoil. Decreasing the stagger distance increases the drag on the aft airfoil, while the fore airfoil experiences an expanded drag bucket and an increased lift-to-drag ratio.