Drag reduction by Gurney – flaps as passive means for flow control.
The associated parasitic drag of these trailing edges can be reduced by passive flow control. By stabilising the wake flow with passive methods a drag and noise reduction is reached. Different types of three dimensional trailing edge configuration e.g. slots, holes or vortex generators have been tested successfully. In addition a partly filling of the wake flow with a streamlined body has been tested successfully too.
For experimental tests on airfoils a wind tunnel with a test section of 1.4m x 2.0 m and a maximum speed of 40 m/s is available. Reynolds numbers of Rechord = 1x106 can be reached for an airfoil. The angle of attack variation, the data acquisition of the wind tunnel balance and the measurement of dynamic pressures and speeds respectively in the wind tunnel are controlled and evaluated by a measuring computer.