Page 285 - Aerodynamics for Engineering Students

(a) Re = SO00 (b) Re = 10 OOO

Fig. 5.44 Vortex breakdown above a delta wing: The wing is made of thin plate and its planform is an equilateral triangle. The vortices are made visible by the use
of dye filaments in water flow. The angle of attack is 20". In (a) where the Reynolds number based on chord is 5000 the laminar vortices that form after separation
from the leading edge abruptly thicken and initially describe a larger-scale spiral motion which is followed by turbulent flow. For (b) the Reynolds number based on
chord is 10000. At this higher Reynolds number the vortex breakdown moves upstream and appears to change form. The flow direction is from top to bottom. See
also Fig. 5.42 on page 266. (The photographs were taken by H. Wer/e at ONERA, France.)