Abstract: A vortex-shedding flowmeter including an annular or ring-shaped vortex-generating bluff body including providing a barrier which at least delays mutual interference between the two streams of vortices generated respectively at the inside and outside surfaces of the bluff body. This may provide either a solid barrier or alternatively a fluid barrier in the form of a stagnation zone between the bluff body and a further ring downstream of it.

Abstract: A device for arresting and/or launching a discrete body at the end of a pline in which the body forms a sliding seal and through which the body is carried by fluid flow comprises a length of pipe continuous with and opening into the pipeline, and having a closed end remote from the pipeline, the internal cross-section of said length of pipe being substantially the same as that of the pipeline; a casing forming a chamber on the exterior of the said length of pipe; an external connection for fluid flow to or from the chamber; and at least one through which the chamber and the interior of the said length of pipe communicate.