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 types are a circular cylinder with a two-dimansional slit along the diameter and a triangular-semicylinder which accompanies alternative boundary layer suction and blowing. The vortex shedding frequency was obtained on the basis of measured fluctuating pressure on the surface of the vortex shedder. The pressure loss of the two shedders with a slit are reduced by 50% compared to that of a trapezoidal cylinder, and the two shedders are superior in linearity, regularity, sensitivity and range ability to the trapezoidal cylinder.