Abstract: Based on flow visualization, dynamic pressure and hot wire measurements, the unsteady phenomena and frequency characteristics in flow over delta wings have been investigated. Spectrum analysis reveals the frequency characteristics of vortex breakdown point oscillation and spiral wave. Experimental results show that the dominant frequency of spiral wave decreases rapidly and then slowly with the increase of the chord-wise position. Oscillation of the vortex breakdown position behaves as the quasi-periodicity in which the frequency keeps almost constant along chord-wise position. It is found that the oscillation energy attains local maximum near the breakdown point. Besides, the test results also show that when the leading vortex breakdown point does not arrive at the top of the tested wing the vortex shedding does exit in the flow over the delta wing.

Key words: delta wing, vortex breakdown, unsteady, spectrum analysis