Oscillation Frequency in Wake of a Vee Gutter

The oscillating behaviors and frequency selection of the unsteady flows in the wake of a vee gutter are studied experimentally in a wind-tunnel by the use of the smoke-wire flow visualization technique and the hot-wire anemometer. The effective length of the vee gutter is determined by the variation of vortex shedding frequency. The functional relationships of the dominant mechanisms in the limiting ranges of Reynolds number are justified by the arguments made on the Strouhal number and the Roshko number. The oscillating motions in the wake region of the vee gutter possess two types of instabilities: the high-frequency shear-layer instability waves and the low-frequency vortex shedding. Four characteristic modes of the shed vortices: laminar, subcritical, transitional, and supercritical, are identified according to the differences of their physical properties. Variations of the Strouhal numbers of the shear-layer instability waves and the vortex shedding are presented and discussed. Characteristic frequencies of the wakes behind various geometries and sharpness of trailing edges are compared.