Masters Theses

Zhi Shi

Date of Award

3-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

J. M. Wu

Committee Members

M. Kurosaka, J. Caruthers

Abstract

An investigation of the leading-edge vortex and the leading-edge vortex break-down on a delta wing has been done. The aim was to study the spectacular and baffling nature of the flow phenomenon with controlled parameters. The work was done in the water tunnel. A delta wing model, which has 55° sweep angle, 12.42 inches span and 10° sharp leading edge, was used in the experiments.

The leading-edge vortex structure was observed with both conventional food color dye technique and laser induced fluorescence dye technique. It was observed that the classical large vortex on a delta wing originates as a series of smaller vortices shed from the leading edge of the delta wing. And it was found that, as the Reynolds number, range from 104to 5x104, increases the vortex breakdown position moves toward the apex. With a forward and a rearward single jet blowing, it was found that both the axial velocity and its gradient significantly affect the vortex breakdown position. A single jet blowing in the direction tangential to the vortex core showed that the tangential velocity is also an important factor for the vortex breakdown. A spanwise blowing indicated that it could significantly delay the vortex breakdown. Periodic spanwise blowing has been tried and showed that a periodic spanwise blowing with very low frequency is influential at low angle of attack up to 25°. It was found that the velocity near the wing apex is an important factor for the vortex breakdown. A pair of symmetrically placed guiding plates could significantly delay the vortex breakdown, and a single guiding plate delays it even more.

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