S = 0.14

a₁)a₃)a₃)a₄)

S = 0.30

b₁)b₂)b₃)b₄)

S = 0.69

c₁) c₂) c₃) c₄)

This animation shows the time dependence of the lowest three surface pressure modes of the surface pressure fluctuations for S = 0.14 (a₁-a₃), S = 0.30 (b₁-b₃) and S = 0.69 (c₁-c₃), respectively. In addition, the combinations of modes which are likely to be responsible for a circular vortex movement around the vortex centre are illustrated in a₄ and c₄ for mode 2 and 3 for S = 0.14 and S = 0.69 and in b₄ for mode 1 and 2 for S = 0.30. The animation is shown with a frame rate of 10fps and consequently relates to an actual measurement time of 2.5 seconds. It is worth mentioning, that the time dependent behaviour and pattern remains constant throughout the entire measurement time of 80 seconds.