In-Flight Flow Visualization Characteristics of the NASA F-18 High Alpha Research Vehicle at High Angles of Attack

Abstract

<div class="htmlview paragraph">Surface and off-surface flow visualization techniques have been used to visualize the three-dimensional separated flows on the NASA F-18 high alpha research vehicle (HARV) at high angles of attack. Results near <i>α</i> = 25° to 26° and <i>α</i> = 45° to 49° are presented. Both the fore-body and leading-edge extension (LEX) vortex cores and breakdown locations were visualized using smoke. Fore-body and LEX vortex separation lines on the surface were defined using an emitted fluid technique. A laminar separation bubble was also detected on the nose cone using the emitted fluid technique and was similar to that observed in the wind-tunnel test, but not as extensive. Regions of attached, separated, and vortical flow were noted on the wing and the leading-edge flap using tufts and flow cones, and compared well with limited wind-tunnel results.</div>