Boundary Layer Trips on Airfoils at Low Reynolds Numbers

Three categories of boundary layer trips (single 2-D plain. multiple 2-D plain, and 3-D trips) were tested on the l\106-13-128, E374, and SD7037 airfoils over t he Reynolds numbers of 100,000 to 300,000. Flow visualization and drag data were acquired for a number of trip heights and locations. To facilitate comparisons between airfoils, t rips were located relative to untripped laminar separation locations. Drag data showed dramatic drag reductions for relatively thin trips, with thicker trips having slightly better performance. The trip location proved to be of little significance for trips located upstream of laminar separation. Little advantage was seen in utilizing multiple 2-D trips or complex 3-D trips over single 2-D trips. Finally, t hrough the application of trips, it was not possible to improve the performance of an airfoil exhibiting large laminar separation bubbles over that of an untripped airfoil with small bubbles.