| Popis: |
A comprehensive study of vortex shedding from bluff bodies in oscillatory flow has been undertaken (Al-Asmi [I], Al-Asmi & Castro [2]). This paper discusses a sub-set of the results, concentrating on the effects caused by the addition of free-stream turbulence. In particular, it is shown that, in the case of a triangular-shaped body, turbulence substantially increases the range of oscillatory driving frequencies (N) over which lock-in conditions occur, provided N is greater than twice the natural shedding frequency, no. The effects depend on the ratio of turbulence integral scale to body size, Lx/d, and the free-stream turbulence intensity, u’/Uo. Increasing either (or both) first extends the lock-in range but eventually leads to ‘saturation’, with further increases in u’/U0 causing a reduction in the extent of lock-in. |
