Flow over a twin-tailed aircraft at angle of attack. I - Spatial characteristics

Abstract

Revised May 5, 1991 Flow Over a Twin-Tailed Aircraft at Angle of Attack. Part I: Spatial Characteristics N.M. Komerath1, S.G.Liou2, R.J. Schwartz3, J.M. Kim3 School of Aerospace Engineering Georgia Institute of Technology Atlanta, Georgia 30332 ABSTRACT A quantitative study is reported on the low-speed flow environment of scale models of a twin-tailed fighter aircraft at high angles of attack. Laser sheet flow visualization is used to observe the various sources of vortex generation, and the evolution of these vortex flows. Surface tufts are used to observe the nature of flow separation on the vertical tails as angle of attack is varied. Laser Doppler velocimetry is used to quantify the time-averaged three-dimensional velocity field, and histograms of velocity, in selected planes proceeding from the inlets to the vertical tails. No concentrated vortex is observed near the vertical tails, however, the tails are seen to be immersed in a vortex flow of large radius. Flow separation propagates up the outside surfaces of the vertical tails, with increasing angle of attack; however, the flow on the inside surfaces of the tails remains largely attached. The flow angularity at the tails varies widely along the tail span, is sensitive to angle of attack, and fluctuates over a wide range at each location. These results are found to be relatively insensitive to the precise modeling of inlet through-flow and inlet attitude. Contours of the root-mean square velocity fluctuations indicate that the largest fluctuations occur in the separated flow immediately above the wing surfaces. ______________ __________________________________________________________ 1: Associate Professor. Member, AIAA 2. Post-Doctoral Fellow. Member, AIAA 3. Graduate Research Assistant. Student Member, AIAA