Shear Thinning Biopolymers Fluids in a Taylor-Couette Flow

Abstract

The current study investigates the effect of shear thinning rheology characteristics of high viscosity non-Newtonian biopolymers on the flow regime characterizations in Taylor Couette flow. The rheology measurements were carried out to investigate the viscoelastic properties of the biopolymers prior to the flow visualization experiments. Both concentrated xanthan gum (XG) and guar gum (GG) solutions were used in this study to investigate their pseudoplastic rheology properties in aqueous solutions over various ranges of concentrations from 0.1%wt to 4%wt. The flow curve and viscoelastic frequency sweep experiments were used to study the rheology of the concentrated biopolymers. The flow curve was performed over the shear rate range of 0.1 s- 1 to 100 s-1 whereas the frequency sweep was performed over the frequency of 0.1 to 300 rad/s. The rheology experiments were performed using a cylindrical head rheometer manufactured by Anton Paar model number NCR-302. The effect of storage time on the solution viscosity and yield stress of both solutions for the concentration of 1%wt was also investigated, with successive viscosity and yield stress stability progress obtained after performing the experiments at the end of each week and after up to 4 weeks of storage period. Additionally, an extra agitation time was applied for the solutions, and it was evaluated three different times 8 h, 24 h, and 48 h of continuous agitation time. After the rheology analysis, the flow visualization investigations experiments using a Taylor Couette system were performed, aiming to study the flow transition characteristics in the Taylor Couette system with a fixed outer cylinder and a rotating inner cylinder. The experiments focused on the flow mapping structure at the onset of each bifurcation for non-Newtonian solutions. We link the flow characterization transition of the shear thinning solutions in the Taylor Couette flow to the viscoelastic and yield stress properties obtained from the rheology analysis for each concentrated solution. Additionally, the flow mapping experiment aims to investigate the effect of the rheology viscoelastic properties such as the shear thinning flow index (n) on the flow mapping main parameters such as critical Reynolds number Re, and the azimuthal variations in the vortex wavelength and vortex count. The Taylor Couette (TC) flow system has numerous applications which depend on the concept of a rotating inner cylinder, including science, engineering, industrial, and fluid processes applications. The TC system is of great interest in the oil field where understanding in needed of the viscoelastic properties of the non-Newtonian fluids that are used as drilling. Additives may3 | Page contribute to the transport of sediments outside the well, by using inducing high viscous muds. The Taylor Couette system is a proper prototype to conduct experiments similar to the downhole walls and rotating string by considering the borehole wall as the outer cylinder and the rotating string as the inner cylinder. Additionally, the Taylor Couette system is also observed in various types of engineering applications, including journal-bearing lubrication, cooling of rotating machinery among others, and purification of industrial wastewater.