Author(s)

T. Wattinger, L. Zartmann & J. Dual

Abstract

Torsional and bending mode vibrations of a hollow cylinder shall be used for combined measurement of density and viscosity of a fluid. The employment of two different vibration modes has the advantage that modes with good sensitivity for either density or viscosity measurements can be used. For a detailed discussion of the dependencies of the sensitivity, a description of the fluid forces and a model of the sensor are required. Analytical solutions for the fluid forces acting on an oscillating cylindrical structure usually consider a two-dimensional situation. FEM simulations are performed in order to investigate the suitability of such solutions in order to describe fluid forces in a three-dimensional situation and for different bending modes. For the case at hand, an analytical relationship between the resonance frequency and the density of the liquid can be formulated. This analytical relationship forms a valuable basis for further investigations. Keywords: vibration sensor, bending, density and viscosity. 1 Introduction In many industrial production processes the control of fluid properties plays a key role. Monitoring of fluid density and viscosity is of particular importance in food, cosmetics, petrochemical, and general chemical industry. Examples of applications are density and concentrationmeasurements in beverages, in intermediate products of refineries or in fuel blends. In the literature several resonator sensors for the combined measurement of density and viscosity are proposed. Krall and Sengers [1] evaluates the damping and oscillation period of an oscillating disk. Da Mata et al. [2] presents a vibratingwire sensor, for which the tension in the wire is determined by the hydrostatic

Keywords

vibration sensor, bending, density and viscosity