Control of Vortex Shedding From a Plate at Incidence Angles in the Range of 0–90 Deg

Abstract

A thin strip cross-sectional element is used to suppress vortex shedding from a plate with a width to thickness ratio of 4.0 at incidence angles in the range of 0–90 deg and a Reynolds number of 1.1×104. The axes of the element and plate are parallel. The incidence angle of the element is 90 deg and the ratio of strip width to plate thickness is 0.5. Extensive measurements of wake velocities, together with flow visualization, show that vortex shedding from both sides of the plate is suppressed at incidence angles in the range of 0–55 deg if the element is placed at points in effective zones. Unilateral vortex shedding occurs if the element is applied at points in unilateral effective zones. The changes in sizes and locations of the effective and unilateral effective zones with the change in plate incidence are investigated, and the mechanism of the control is discussed. Two patterns of unilateral vortex shedding are observed. Pattern I occurs on the side where there is no element, and oppositely, pattern II occurs on the side where the element resides. A resonance model is proposed to illustrate the occurrence of pattern II unilateral shedding. The phenomenon of unilateral vortex shedding means that the vortex can be generated without strong interaction between the shear layers separated from the bluff body.