Numerical Investigation of the Flutter Behaviour of a Laminar Supercritical Airfoil

Kurzfassung

Nowadays drag reductions are important also in aircraft design. Natural laminar flow on aircraft wings is therefore preferred over chaotic turbulent flow. So-called laminar airfoils can be used to achieve (partly) laminar flow. Laminar flow should however not lead to a reduction in the capabilities of an aircraft. Since the flutter boundary is one of the most important boundaries of the flight envelop of an aircraft it is important to investigate the effect of laminar flow on this boundary. Since this has not been investigated yet, a first step was taken in this work by the use of numerical simulations. CFD simulations with and without boundary layer transition were performed to obtain the generalised airloads. Using a two-degrees-of-freedom structural model the flutter boundary was computed. The minimum of this boundary, the so-called transonic dip, was found to be lower in case of free boundary layer transition compared to the fully turbulent case. Hence, the flutter behaviour of a laminar supercritical airfoil seems to be more critical in (partly) laminar flow at transonic conditions than in case of fully turbulent flow.