Affiliations: School of Mechanical and Aerospace Engineering,
Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore. E-mail:
[email protected]
Abstract: This paper studies the effect of perturbation to the breakdown of
the leading-edge vortices over delta wings. The passive perturbation in the
normal direction is achieved by installing the hemisphere-like bulges on the
delta wing along the projection of the vortices. The key purpose of this
perturbation is to delay or suppress vortex breakdown over delta wings
according to the self-induction mechanism theory. The design of bulge-like
surface for delta wings offers a minimization of initial vorticity gradient and
an elimination of linearly mutual induction within the vortex core. Three delta
wings with swept angles of 60°, 65° and
70° have been used. Dye flow visualization and force measurement
in different water tunnels are performed at the water speed of U=0.10, 0.15,
0.20 and 0.25 m/s. In flow visualization, the results show contributions of
bulges as perturbation to leading-edge vortices. The best outcome of perturbing
the vortex core occurs in the case of the 65° delta wing. The
breakdown positions on the 65° delta wing are delayed in almost
the entire range of angles of attack, and that, the results are presented here.