Investigation into Scale Effects on the Performance of Sub Boundary-Layer Vortex Generators on Civil Aircraft High-Lift Devices

Abstract

The need to control flow separation on a single slotted trailing -edge flap generally requires the wing/flap gap to be small. At these small gaps, the aerodynamic parame ters can become sensitive to small changes in flap position. The need to maintain the gap within specified tolerances in flight conditions over the span of the device imposes requirements on the relevant structures and deployment mechanisms. These requirem ents result in solutions that have weight and cost implications. Flow control devices, such as Sub Boundary -layer Vortex Generators (SBVGs), have been found to be effective in reducing flow separation where it arises. This paper describes the results of an experimental study of the application of SBVGs to civil aircraft high -lift devices at high Reynolds number. The * investigation followed an assessment of various types of SBVG and their performance in an adverse pressure gradient conducted in a specialised low speed wind tunnel. The most effective devices were then tested at low Reynolds number in atmospheric wind tunnels, applied to the trailing -edge flaps of both a simplified, though three -dimensional, half model and a fully -representative half -model of a civil aircraft. The examination of the same devices on the same models at high Reynolds number in a pressurised wind tunnel will then be described. The paper will cover these low -speed wind -tunnel tests on two civil transport models, conducted in order to study the effectiveness of SBVGs in controlling flow separation on a slotted trailing -edge flap, and show how this is influenced by variation of Reynolds number.