Flow Resistance and Strouhal Number of a Vortex Shedder in a Circular Pipe.

Experimental studies were carried out on the performance of three vortex shedders used for vortex flowmeter in a circular pipe: one is a trapezoidal cylinder used as a practical device and the other two are a circular cylinder with a two dimensional slit along the diameter and a triangular-semicylinder which accompanies alternative boundary layer suction and blowing. The vortex shedding frequency was measured by the fluctuating pressure on the surface of the vortex shedder. The pressure loss of the two shedders with a slit is reduced by 50% compared with that of a trapezoidal cylinder, and the two shedder is superior in linearity, regularity, sensitivity and range ability to the trapezoidal cylinder.