Unsteady High-Lift Aerodynamics – Unsteady RANS Validation An Overview on the UHURA Project

Abstract

Laminar wing technology is seen as the major single source for drag reduction on the airframe of a transport aircraft and will be a key technology to achieve the targets for emission reduction. In recent EC funded projects, the Krueger flap leading edge device was found to be the most promising concept of a dual-functional leading-edge device for laminar wings. While the these studies focused on the general performance and integration, the behavior of the system during its deployment or retraction proves to be a major issue due to the very different kind of motion compared to conventional leading edge high-lift devices. The risks of this concept are identified in the areas of load estimates, handling qualities and asymmetric failure cases. During the deployment, the Krueger device is deflected from the lower side against the flow, passing critical stations when perpendicular to the flow, forming large scale separated flow on the lower side when moved around the leading edge (Figure 1). Current conservative estimations require the installation of many independently driven Krueger flap elements to prevent examination of critical situations along the whole wing span. The multiplication of drive stations leads to increasing complexity, weight and maintenance costs. On the other hand, despite the great progress in numerical simulation methods in the past years, there have up to now been no investigations on the validity of the current methods for predicting the behavior regarding these critical topics. The aerodynamics during movement of high-lift devices have not yet been addressed in detail. The project UHURA is focusing on the unsteady flow behavior around high-lift systems and will first time deliver a deeper understanding of critical flow features at new types of high-lift devices of transport aircraft during their deployment and retraction together with a validated numerical procedure for its simulation. UHURA performs detailed experimental measurements in several wind tunnels to obtain a unique data set for validation purposes of Computational Fluid Dynamics (CFD) software, including detailed flow measurements by Particle Image Velocimetry (PIV) and other optical measurement technologies. Advanced CFD methods promising significant improvements in the design lead time are validated against this database to obtain efficient and reliable prediction methods for design.