Overview of the Wind Tunnel Tests with Suction in the DNW-NWB

In the low speed wind tunnel Braunschweig (DNW-NWB), three measurement campaigns with sucked boundary layer for laminarisation have taken place. Their aim was to improve effectiveness and efficiency of HLFC systems on the path to industrial applications. The present article gives an overview over the modular wind tunnel model, the conducted measurement series and the obtained results. Multiple suction surfaces were used. Conventional approaches with laser drilled cylindrical perforations are compared with recently developed suction surfaces, using a fine etched metal foil and a supporting mesh structure. Also two layouts of suction slots in contrast to the cylindrical perforations are considered. All investigated surfaces turned out to be suitable for transition delay. Differences of the effectiveness between the suction panels could be found depending on the suction rate. Moreover, numerical investigations are presented, allowing a deeper insight into aerodynamical processes of unstable boundary layer modes. The focus was on the deviation of experimentally measured transition lines and numerical predictions by an \(e^N\) method with regard to effectiveness of suction and predictability.