FLOWFIELD MEASUREMENTS OF A TWO-ELEMENT AIRFOIL WITH LARGE SEPARATION

Detailed measurements of moderate to large separated flows have been made for the 13%-thick GA(W)-2 airfoil with 25% slotted flap at a Reynolds number of 2.2 x 106 and Mach number of 0.13. The tests were made for flap nested and flap deflected cases of 30- and 40-deg flap angles with optimum and narrow gaps at near- and poststall angles of attack. The data include pressure, mean flow, and turbulence quantities. A splitter plate was employed for measuring a large number of static pressures simultaneously. Flowfield sensitivity to the measuring probes was determined by means of force and surface pressure measurements. The experimental program revealed the difficulty of measuring pressures in separated flows. The presence of a probe, no matter how small, changes the flow geometry in the interacting parts of the flowfield. The results of this experimental study are sufficiently detailed to serve to evaluate computational codes of such separated flows on multielement airfoils.