Review and classification of various aerodynamic and hydrodynamic means for suppressing vortex shedding

Abstract

A wide variety of aerodynamic and hydrodynamic means for suppressing vortex shedding is classified into three categories in accordance with the phenomenological mechanism of vortex shedding. The three categories are as follows: 1. (i) surface protrusions, which affect separation lines and/or separated shear layers, e.g. helical strakes, wires, fins, studs or spheres, etc.; 2. (ii) shrouds, which affect the entrainment layers, e.g. perforated, gauze, axial-rod, axial-slat, etc.; (iii) nearwake stabilisers, which prevent interaction of entrainment layers, e.g. splitter plates, guiding vanes, base-bleed, slits cut across the cylinder, etc . Most means in the first two categories are omnidirectional, i.e. they are effective irrespective of the direction of fluid velocity. Some means in the first and all in the third category are unidirectional, i.e. they are effective only for one velocity direction. All means are described in detail and the reasons for their effectiveness explained. A comparative assessment of effectiveness is attempted and the need for comparative tests of various means under identical model conditions is stressed. The reduction of effectiveness in the post-synchronisation range, at high intensity of turbulence, and due to multi-cylinder interference is emphasised.