EVOLUTION OF AN IMPROVED VORTEX GENERATOR

This paper reviews the process, stretching over several years and with contributions from several workers, by which an improved body shape for use in vortex shedding meters was designed and tested. A priori knowledge of the fluid mechanics involved in vortex shedding, supplemented by information obtained from observation (flow visualization) and measurement (spectral analysis), was used to direct the design process. Particular attention was focused on stabilizing the vortex shedding so that signal dropout and unnecessary limitations to the operating range could be attacked at their source. After examination of the performance of a number of different cylinder cross-sections, and experiments involving splitters and afterbodies, a detailed study of a generator consisting of a circular cylinder split across its lateral diameter was undertaken. Subsequently, it was found that the performance of this (already good) generator could be improved still further by shaping the rear surface of the cylinder. The split cylinder with concave rear surface resulting from this design process was shown to provide the strongest and most regular vortex shedding of all the shapes tested. Moreover, the performance benefits of this shape can now be explained in terms of the flow structure in the near wake.