Measurements in the wake flow behind finite circular cylinders fitted with slat devices

In this paper the influence of a slat device upon the wake flow behind a finite circular cylinder is investigated. Frequency and cross-correlation (in time) measurements are carried out at a Reynolds number of 31000 and at several streamwise and lateral positions in the near wake of a plain circular cylinder and a circular cylinder fitted with the slat device. The resulting modifications of the wake pattern due to the slat device are discussed. It is shown that the presence of the slat device increases the length of the vortex formation region and thus delays the formation of a periodic vortex wake to relatively long distances behind the body. It is this delay that is largely responsible for the effectiveness of the slat device in suppressing large amplitude vortex-induced oscillations of circular cylindrical bodies.