Abstract: Systems and techniques are described making use of a vibratory transducer and a reflector spaced from the vibratory transducer to form a cavity for receiving a fluid between the vibratory transducer and the reflector, wherein the vibratory transducer is vibrated to generate a wave in the cavity, which propagates through fluid in the cavity from a surface of the vibratory transducer and is being reflected by the reflector to generate a counter-propagating wave in the cavity. Based on the wave generated at the vibratory transducer and the counter-propagating wave generated at the reflector in combination, an indication of the energy returned to the vibratory transducer by the reflector is determined. One or more material properties of the fluid are determined based on the determined indication of the energy returned to the vibratory transducer.

Abstract: A model of the viscoplastic boundary layer of a yield stress fluid is described and, based on which, there is provided a method of estimating the yield stress of a flowing yield stress fluid using one or more vibratory transducers having a vibratory surface in contact with the yield stress fluid, the method comprising: vibrating a vibratory surface of a vibratory transducer to transmit a wave from a vibrating surface into a viscoplastic boundary layer of the flowing yield stress fluid, the wave propagating a distance into the viscoplastic boundary layer; making, using the vibrations of the vibratory transducer, one or more measurements of the degree of damping of vibration; and estimating the yield stress of the flowing yield stress fluid based on the one or more measurements of the degree of damping of vibration. There are disclosed single-frequency, dual-frequency and triple-frequency modes of operation.

Abstract: A model of the viscoplastic boundary layer of a yield stress fluid is described and, based on which, there is provided a method comprises the steps of: vibrating a vibratory transducer at resonance at a first resonant mode in a yield stress fluid and making a first measurement of the resonant frequency; providing a vibration to liquefy at least a portion of the yield stress fluid around the one or more vibratory transducers; while said portion of the yield stress material is liquefied, vibrating a vibratory transducer at resonance at the first resonant mode in the yield stress fluid and making a second measurement of the resonant frequency; and estimating the yield stress of the yield stress fluid based on the first and second measurements. The vibration to liquefy yield stress fluid around the one or more transducers may be provided by the making of the second measurement at an increased amplitude of vibration relative to the first measurement.

Abstract: Apparatuses and methods are disclosed for the analysing of non-Newtonian fluids and determining parameters to characterise the relationship between shear stresses and shear rates, i.e. the parameters of one or more rheological models of viscosity. A plurality of viscosity measurements are made in a fluid using one or more vibratory transducers operating at a plurality of frequencies. Parameters for the fluid are determined based on the measured viscosity values and the frequencies of vibration at which the viscosity measurements were obtained.

Abstract: Apparatus for the measurement of a fluid property is shown generally at (10). The apparatus is typically suitable for the measurement of a property of a fluid (not shown) such as its viscosity, and comprises a tube (12) for the through-flow of fluid to be measured, a torsion bar (14), a magnetic drive coil (16) and a magnetic pick-up coil (18). The tube (12) is mounted within a casing (20), shown in cutaway. An inertial frame (22) is secured to the casing via isolators (not shown). The tube (12) has a web portion (24) supporting inertial masses (26) connected to, and radially spaced from, the tube (12). The tube is connected at each end to pipe fittings (28) via end flanges (30) and seals (32). The single tube (12) has been selectively machined to produce areas (12a) of low compliance which effectively form springs. The torsion bar (14) is of relatively low inertia and is fixed at the midpoint of the length of the tube (12).

Abstract: A sensor of force or viscosity or other attributes of a fluid comprises a mechanical resonator (10) including an element (11; 18; 123) of which the stiffness at least partially determines a modal shape of the resonance of the resonator and means (21-23) for measuring a variation of a measure of the resonance as the stiffness of said element changes. The resonator (10) may comprise two beams (10a, 10b; 120, 121) connected at or near one end by a yoke (12; 122) which provides a clamped condition of the resonator at said one end and connected at or near another end by said element.

Abstract: An instrument for the detection or measurement of attributes of a material comprises at least one vane which is mounted on a support that allows the vane to vibrate, a drive transducer which is disposed relative to the vane to stimulate vibration therein and at least one sensing transducer disposed to sense the vibrations.