Waele Power Law Research Articles

Computational Analysis of Rheological Secondary Flow in a Pipe-Manifold Containing In-Plane Double Bends

Non-Newtonian fluid flow in pipe bends is inevitable in industrial applications. Previous researchers have extensively explored Newtonian flow through curved ducts. However, the non-Newtonian counterpart gets little attention. We study the turbulent flow of shear-dependent fluids obeying the Power-Law model in a pipe manifold containing an in-plane double bend. Ostwald–de Waele's power law is used to model the fluid's rheology. We utilize computational fluid dynamics (CFD) to solve Reynolds-averaged Navier–Stokes (RANS) equations with the k-ε turbulence model. We validate our numerical results with previous experimental results. The in-plane double bend perturbs the flow in the pipe manifold to develop a Prandtl's secondary flow of the first kind. A fully developed flow at the bend upstream is disturbed due to the bend's curvature and regains its fully developed characteristics upon a certain downstream length after the exit of the bend. We study the rheological characteristics of the secondary flow within the bend and the evolution of fluid flow at the bend downstream. We demonstrate that the centrifugal force-dominated secondary flow increases with a decrease of the non-Newtonian power-law index. We capture the camel's-back-shaped velocity profiles within the bend due to accelerating-decelerating flow. The study reveals that the average flow velocity increases along the bend with a corresponding pressure head loss. We quantify this velocity rise by a newly introduced non-dimensional number, viz. enhancement ratio. The double bend's enhancement ratio decreases with an increase in n.

Physical and rheological\xa0properties of the Chorfa dam mud: dependency on solids concentration

The main purpose of this study is to determine the mud rheological properties of the Chorfa dam (region of Mascara, Algeria) and to propose a rheological model that describes mud flow behavior. This study helps on one hand to give a better understanding of fine sediment transport dynamics in the dam, as well as contributing to reduce the dredging costs, and on other hand to valorize dredged sediments in road construction. Rheological measurements were conducted using an Engler viscometer and a Haake RS 600 rheometer. Mud samples were prepared with purified water at a range of solids concentration varying between 5.0 and 32.5%. Besides, the physical, chemical and mineralogical characteristics of the Chorfa dam’s mud and the rheological tests were presented and the effect of solids concentration on mud viscosity was studied. The results indicate that the Chorfa dam’s mud showed a non-Newtonian behavior for solids concentration higher than the critical solids concentration, and the apparent viscosity increases with increasing solid concentration at different shear rates. In addition, for a fixed concentration, the apparent viscosity decreases with increasing shear rates, which approves the shear thinning behavior of the Chorfa dam’s mud. Fitting results of four rheological models (Bingham Plastic Model, Ostwald–de Waele (power law), Herschel–Bulkley and Casson) to the experimental data were presented. Hence, the Ostwald–de Waele model was the best fitting model for mud samples.

Controlling shear thinning property of lime silica based mold flux system with borate additive at 1623 K

We have studied the shear thinning property of mold flux with borate additive using a rotational type rheometer at various shear rates. Mold flux at 1623K is currently used in the steel industry as a lubricant to reduce the shear force exerted on a solidifying steel shell in an oscillating mold. In an actual casting process, the enhancement of shear thinning property might be beneficial for a casting process. Therefore, the present study is designed to control the shear thinning property of mold flux at 1623K by changing a borate concentration. For the first step of the present study, Raman spectroscopy is used to identify structural change of mold flux with increasing a borate concentration. The second step is to conduct viscosity measurement by changing shear rates with a rotational rheometer. The degree of shear thinning has been successfully estimated by the flow behavior index of Oswald–de Waele's power law. In doing so, we successfully achieved the strong shear thinning property of mold flux and discovered the rationale behind this. In order to maximize the shear thinning property of lime silica based glass forming liquid, it is essential to understand the degree of polymerization (DP) and stiffness of entire mold flux structure.