Karman vortex flowmeter is widely used for measurement of flow rate in a pipe flow. In this method, the flow rate is measured by the vortex shedding frequencies from a two-dimensional cylinder. Under the uniform flow condition, the frequency of vortex shedding caused by the two-dimensional cylinder is directly proportional to the flow velocity and is inversely proportional to the size of the cylinder. The proportional constant is called the Strouhal number, which has individual proper value for the shape of the vortex shedder over a wide range of Reynolds numbers. 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-dimensional 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.
Flow resistance and Strouhal number of a vortex shedder in a circular pipe
Strömungswiderstand und Strouhalzahl eines Wirbelablösers in einem Kreisrohr
JSME International Journal, Series B (Fluids and Thermal Engineering) ; 42 , 4 ; 586-595
1999
10 Seiten, 16 Bilder, 3 Tabellen, 16 Quellen
Aufsatz (Zeitschrift)
Englisch