Among the many different flow meters available today perhaps vortex flowmeters
are the most difficult for the layman to understand. Vortex flow meters place a bluff body (called a shedder bar) in the path of the fluid. The fluid passing this bar creates disturbances in the flow called vortices. The vortices trail behind the cylinder, alternatively from each side of the bluff body. The frequency at which these vortices alternate sides is essentially proportional to the flow rate of the fluid.