Application of a Ring to a Bluff Body of a Vortex Shedding Flowmeter

This paper is concerned with vortices shedding from rings, which can be expected to have many advantages as the bluff body of the vortex shedding flowmeter for the industry and the standard of the flow velocity.Regarding patterns of vortices shedding from rings, d/w is thought to be the most dominant parameter by analogy with patterns of vortices shedding from two cylinders, where d is a mean diameter of the ring and w is a width of the ring. This supposition is confirmed by the observation of vortices shedding employed a flow visualization technique and a hot-wire anemometer, and it is also clarified that the most stable vortex rings shed from the ring which the diameter is 20mm d/w=6.1, and they are more stable than vortices from a plate. The sinusoidal detecting signal of vortices shedding, which is free from the effect of the turbulent shear layer, can be obtained by a hot-wire anemometer at the behind of the center of this ring. Althrough the Strouhal number slightly changes with the Reynolds number, as the velocity profile around the ring changes with the flow velocity, the repeatability of the frequency of the vortex to the flow velocity is within 0.1%.