Linear viscoelastic analysis using frequency-domain algorithm on oscillating circular shear flows for bubble suspensions

Abstract

To achieve a stable evaluation of the linear viscoelasticity of bubble suspensions, which have difficulties for conventional rheometers from spatial distributions of rheological properties with bubble deformations, we proposed a novel rheometry based on spatiotemporal velocity data obtained by ultrasonic velocity profiling (UVP). A frequency-domain algorithm was adopted to overcome a critical influence of measurement noise on the rheological assessment, which is inferred from error propagation characteristics through the equations of motion in discretized form. Applicability and advantage of the present rheometry with the frequency-domain algorithm were verified by two kinds of fluids; high viscous oil as a Newtonian fluid, and polyacrylamide aqueous solution as a shear thinning, viscoelastic fluid. The rheometry was finally adopted for bubble suspensions subject to high oscillatory shear, and it could validly extract elasticity-originated momentum transfer as a function of space.

Color-coded visualization of microbubble clouds interacting with eddies in a spatially developing turbulent boundary layer

“…Once the clouds are formed, microbubbles cannot be directly simulated under the assumption of point source. Inside such a cloud, volume fraction and interfacial concentration rise sharply to modify local fluid properties such as density, viscosity and viscoelasticity [15,16,17]. The generation is promoted as the slip velocity of microbubbles to liquid phase is rather small.…”

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.…”

“…Most recently, Tasaka et al (2018) achieved a stable evaluation of the linear viscoelasticity in bubble suspensions as complex multiphase fluids using USR. From these branches of applicability in previous reports, USR system raises the possibility of evaluating rheological properties in complex fluids in more robust methodology than conventional rheometry, such as rotational torque rheometry.…”

Overview of Ultrasonic Spinning Rheometry: Application to Complex Fluids

“…2.0 which is viscoelasticity evaluation algorithm in a frequency domain. 16) Basically, optimal properties are determined by substituting velocity profiles into the motion and constitutive equations. Completed by velocity measurement alone, multiple rheological properties can be evaluated without additional measurement.…”