Validation experiment on a passive suction flap for Hybrid Laminar Flow Control applications

Current designs for Hybrid Laminar Flow Control (HLFC) systems on aircraft wings often feature passive suction flaps to provide the required suction mass flow instead of or in addition to an active compressor system. This work presented herein, performed within the German LuFo-funded project OptiHyL, aims at a deeper understanding of the complex flow physics of such a flap in the high subsonic regime and at the creation of a validation database for simulation-aided design. In order to achieve that, a generic wind-tunnel model of a 2D airfoil featuring a flap and ducting has been tested at the Transonic Wind Tunnel Göttingen (DNW-TWG). The meas-urements included forces, moments, surface pressures on the airfoil and within the ducting, mass-flow through the flap and flow topology via PIV. The major experimental findings are discussed in this article alongside first promising CFD RANS simulation results