Studies on the Instabilities of the Float of Float-Area-Type Flow Meters : 1st Report, Conditions for the Occurrence of Rotational Vibration of a Float

Abstract

In order to establish the limits of applicability and to define the accuracy of float-area-type flow meters, studies on instabilities of the float were performed. From the behaviour of the float, types of instabilities were classified into three when the float with stabilizer was employed and into four when the without stabilizer was employed. In this report, studies were made on the causes for one of the instabilities, classified above for the float without stabilizer, which was the rotational vibration of the float. It was shown that there existed three kinds of causes, the first of which was the resonance between the natural frequency of the rotational vibration of the float and the frequency of periodic hydraulic forces acting on the float, the second was the transition from laminar to turbulent of the flow in the clearance between the float and the tapered tube adn the third was the correlation between the position of the centre of gravity of the float and the hydraulic forces acting on the float.