NUMERICAL ANALYSIS OF GENERALIZED AERODYNAMIC FORCES CONSIDERING LAMINAR-TURBULENT TRANSITION ON A NLF WING

The wing’s dynamic aeroelastic stability analysis, referred to as flutter analysis, typically involves potentialflow-theory-based methods to model unsteady aerodynamics, which do not consider viscous or non-linear effects. Modern sailplane wings with Natural-Laminar-Flow (NLF) airfoils present significant chord-wise runs of laminar boundary layers. Assuming an inviscid or completely turbulent flow over the wing chord could result in completely wrong predictions of the unsteady aerodynamic characteristics of the wing and, hence, an inaccurate prediction of the dynamic aeroelastic behavior. This study presents a coupled Finite Element beam model of a sailplane with a Computational Fluid Dynamics model to calculate the Generalized Aerodynamic Forces (GAF). The aeroelastic behavior is investigated by means of aerodynamic damping and stiffness. The influence of transition on the unsteady aerodynamic response of a modern sailplane’s NLF wing is investigated numerically with the Gamma-Transition Model for a range of Re-numbers and reduced frequencies kred. The GAF entries are compared to the results obtained with the fully turbulent Spalart-Allmaras (SA) model.