Stabilized vortex-shedding flowmeter

A stabilized vortex-shedding flowmeter comprising:

• A. a flow tube through which a fluid stream to be metered is conducted, said tube having a longitudinal flow axis;
• B. a front obstacle having a predetermined geometry transversely disposed in said tube to divide the fluid stream therein and to cause vortices to be shed alternately on either edge thereof at a repetition rate proportional to the flow rate of the fluid, thereby producing downstream trains of vortices moving along the right and left sides of the tube;
• C. a rear obstacle fixedly supported in the tube behind the front obstacle and mechanically disconnected from the front obstacle to define an unobstructed gap therewith, said rear obstacle being constituted by a pair of parallel relatively broad beams symmetrically disposed with respect to the flow axis and lying in a plane normal thereto, the beams being restrained to remain in a plane transverse to the flow axis, the divided fluid stream, as it flows past the front obstacle, developing a stagnant zone in the gap that is initially aligned with the flow axis;
• but as vortices are successively detached from the front obstacle and appear alternately on either side of the gap, the low pressure produced by each vortex acts to draw the stagnant zone in front of the beam adjacent thereto, the fluid then going around and past the other beam and imposing a drag force thereon, the drag forces on the beams alternating at a flow rate proportional to flow rate to produce an alternating movement of the stagnant zone that is bi-stable regardless of fading, turbulence and other disturbances;
• and
• D. transducer means for sensing said alternating movement in said tube to produce a corresponding electrical signal.