Ultrasonic velocity profiling rheometry based on a widened circular Couette flow

Abstract

We propose a new rheometry for characterizing the rheological properties of fluids. The technique produces flow curves, which represent the relationship between the fluid shear rate and shear stress. Flow curves are obtained by measuring the circumferential velocity distribution of tested fluids in a circular Couette system, using an ultrasonic velocity profiling technique. By adopting a widened gap of concentric cylinders, a designed range of the shear rate is obtained so that velocity profile measurement along a single line directly acquires flow curves. To reduce the effect of ultrasonic noise on resultant flow curves, several fitting functions and variable transforms are examined to best approximate the velocity profile without introducing a priori rheological models. Silicone oil, polyacrylamide solution, and yogurt were used to evaluate the applicability of this technique. These substances are purposely targeted as examples of Newtonian fluids, shear thinning fluids, and opaque fluids with unknown rheological properties, respectively. We find that fourth-order Chebyshev polynomials provide the most accurate representation of flow curves in the context of model-free rheometry enabled by ultrasonic velocity profiling.

Flow Prediction of Complex Fluids in a Circular Pipe by Utilizing a Velocity-Profiling-Assisted Rheometer

“…Neither the stepped cylinder nor rods are in contact with the inner cylinder, so the torque sensor measures axial torque that is caused solely by simple shear stress acting on the inner cylinder wall. This is an improvement over the velocity profiling-assisted rheometer described in previous studies, 21,25,26 which simply consisted of inner and outer cylinders. This experimental apparatus is, nevertheless, a prototype and therefore has some shortcomings, such as its large size and the fact that the inner cylinder is also filled with the test fluid.…”

Rheological properties of montmorillonite dispersions in dilute NaCl concentration investigated by ultrasonic spinning rheometry

“…We proposed a rheometry using UVP for complex fluids in rotating cylindrical system without requiring an inner cylinder to measure the axial torque, termed ultrasonic spinning rheometry (USR) (Shiratori et al, 2013(Shiratori et al, , 2015Tasaka et al, 2015;Shiratori et al, 2016;Yoshida et al, 2017;Tasaka et al, 2018).This technique can be applied even for opaque liquids and for complex fluids.…”

“…Different simple shear conditions are realized as spatial distributions by setting the oscillation frequency f and the amplitude Θ to different values. Shiratori et al (2015) proposed a model-free USR for the quantitative evaluation of a shear-rate-dependent viscosity without using any rheological models. A supplemental axial torque measurement was used to satisfy the boundary conditions to solve the equations of motion.…”

Ultrasonic velocity profiler applied to explore viscosity–pressure fields and their coupling in inelastic shear-thinning vortex streets

“…In industry relevant opaque fluids, PIV is also not applicable. Thus, ultrasound velocity profiler (UVP) (Takeda 2012;Shiratori et al 2015) is a promising and valid choice. UVP uses a single ultrasound transducer to provide one-dimensional, one-component (1D-1C) velocity distributions.…”