Dye Visualization of a High-Angle-of-Attack Translating Wing Experiencing Ground Effect*

Ground effect (GE) happens when an aircraft flies near a lower boundary, increasing lift and lowering induced drag. At high angle of attack, the aircraft experiences unsteady flow due to vortices forming and shedding, substantially influencing lift. A small, maneuvering drone can experience flow separation and GE when above obstacles, and in real applications the ground length will be finite. This study uses a water towing tank with a translating, fixed-angle-of-attack wing and dye visualization to show the leading- and trailing-edge vortices and their interactions with finite ground obstacles. The tip-to-bottom-wall gap of the vertically-towed wing is small to help supress tip effects and simplify the interactions, and the grounds are rectangular. A gravity-feed system and small tubes on the wing deliver dye to the vortices, and dye is used to clearly show the ground interactions, via multiple colors. This project builds on the group's prior work which includes lift measurements and limited particle image velocimetry, for comparison and to form a more complete understanding of the interactions. The dye system is designed with minimum complexity to make it compatible with almost any setup in future studies.