Control Surface Reversal in the Transonic Regime Including Viscous Effects

Abstract

This paper investigates control surface reversal in the transonic flight regime. Surface-pressure distributions on a rigid and deformable wing are presented using linear and nonlinear aerodynamic methods, which incorporate the effects of surface shocks and viscosity with an interactive boundary layer. Transonic small-disturbance (TSD) aerodynamics is used to determine reversal of a typical fighter wing to study the interactions among control surface deflections, structural flexibility, and embedded shocks in a flowfield where significant viscous effects can exist. Pressure distributions on the wing are examined, and control surface reversal calculations are presented. The results show that the reduction of the reversal dynamic pressure can be as much as 30% when an aerodynamic method capable of representing a shock is used. A limited number of Euler computational fluid dynamic (CFD) results are presented for the purpose of comparison with transonic small disturbance results. The adequacy of using TSD theory in reversal prediction as compared to that obtained from either Euler or Navier-Stokes CFD aerodynamics is discussed. It is suggested that the inviscid transonic small disturbance aerodynamic provides a capability of representing shocks with only a modest increase of computer time beyond that necessary with the linear surface panel method. It is recommended that the inviscid version of TSD be incorporated in the preliminary design of aircraft operating at transonic speeds.