A computational assessment of viscosity measurement in rotating viscometers through detailed numerical simulation

Abstract

The viscosity values of slags and metals constitute important kinetic data and, therefore, are of considerable importance to the modeling and controlling of various metallurgical processes. Naturally, therefore, significant efforts have been made by researchers to measure the viscosity of a diverse range of metallurgical melts. [1][2][3][4][5][6][7][8] In practically all of these investigations, a rotating viscometer, either with a rotating crucible [8] or a rotating cylinder/spindle, [1][2][3][4][5][6][7] has been applied. A typical measurement, for example, involves imparting a rotational motion to either the crucible or the spindle and recording the corresponding equilibrium torque experienced by the cylinder or the spindle, i.e., the entire submerged assembly, as in Figure 1. From the measuredtorque, melt viscosity is deduced following one of the two popular approaches:1. a technique relying entirely on calibration, [1] in which a torque vs viscosity relationship established a priori from standard melts is applied to translate the measured torque into viscosity; and 2. a simplified one-dimensional momentum transfer analysis wherein wall shear stress inferred from the measured torque is equated against the corresponding shear strain rate and thereby melt viscosity is determined. [7] According to the simplified theory of flows in rotating viscometers, [7,9] the viscosity of the liquid or melt is obtained by dividing the shear stress with the corresponding shear strain rate, both evaluated at the spindle surface (Figure 1), e.g.,In Eq.[1], and are the shear strain rate and the shear stress at the cylinder/spindle surface and are, respectively, given by [7,9] [2]and [3] t ϭ Q 2pR spindle 2

A novel design of flow structure model for online viscosity measurement

“…In addition, the rheological behaviour of the fluid cannot be easily included in the offline measuring process. Online methods, such as vibration viscometry [13,14] and rotating viscometry [15,17] , are able to measure the fluid viscosity without destroying the rheological behaviour of the fluid. For example, Etchart et al [17] successfully measured the viscosity of a fluid with obvious rheological behaviour using vibration viscometry, Janeiro et al [18] used vibration viscometry to achieve fluid impedance spectroscopy and Diogo et al [19] utilised vibration viscometry to measure fluid viscosity with different chemical components and temperatures.…”

A New Method for Liquid Viscosity Measurements: Inclined-Tube Viscometry

“…Viscosity measurements are important for production flow control, guarantee of the production safety, control and evaluation of product quality, medical diagnosis, and scientific research. According to the different measuring principles, traditional viscometry can be grouped as follows: capillary viscometry [3][4][5][6][7][8], rotating viscometry [9][10][11], falling ball or needle viscometry [12][13][14][15], vibration viscometry [16][17][18][19], etc.…”