Visualized vortices on unmanned combat air vehicle planform: Effect of Reynolds number

The Reynolds number dependence of the vortex patterns on a representative unmanned combat air vehicle (UCAV) planform is defined. It is defined in terms of the onset of pronounced instability/abrupt breakdown of the vortices from the wing root and the degree of interaction of the vortices from the apex and the wing root. The onset of pronounced instability/breakdown is highly sensitive to Reynolds number at relatively low angle of attack while it is much less sensitive at high angle of attack. It is found that the effective sweep angle of the wing root vortex is a function of Reynolds number. With a decrease in angle of attack, the Reynolds number at which the vortices from the apex and the wing root cease to interact decreases substantially.