Opis: The incompressible non-Newtonian fluid flow through a symmetric sudden expansion is studied numerically in order to obtain Reynolds number critical value. The Quadratic model is employed to accommodate the shear-thickening behavior of corn-starch and water mixture. Numerical procedure is validated with results for the Newtonian fluid flow in a range of the Reynolds number Re=10,20,.,100. Results for the non-Newtonian fluid show that the shear-thickening behavior lowers the threshold of the transition from flow symmetry to its asymmetry (lowers the onset of the bifurcation and the critical value of the Reynolds number) and increases the reattachment length. In addition, the results for the Quadratic model are compared to the results obtained with the Power law. Ključne besede:fluid mechanics, bifurcation, sudden expansion, shear thickenningfluid, quadratic model, powr law Objavljeno: 31.05.2012; Ogledov: 996; Prenosov: 23 Povezava na celotno besedilo

Opis: In the paper a new rheological model for an electrostatic ash and water mixture is proposed. The fundamental equation of the rheological model was used to determine the relationship between the shear stress and the shear rate as well as the equation of a velocity profile for the flow through a straight pipe. Experimental results obtained from a capillary viscometer were used as the basis to determine the parameters for the proposed model by the non-linear regression analysis. With the Quadratic law a numerical analysis of a mixture flow through a capillary pipe with the finite volume method was performed. The derived equations for the velocity profile, shear stress and shear rate were validated through a comparison of numerically obtained and theoretical results. Finally, the compariosn between the Quadratic and the Power law is presented. Ključne besede:fluid mechanics, non-Newtonian fluids, mixture of electrofilter ash and water, flow in pipes, capillary pipes, rheological model, velocity profile, shear stress, finite volume method, numerical analysis, quadratic law, power law, mehanika fluidov Objavljeno: 01.06.2012; Ogledov: 1418; Prenosov: 15 Povezava na celotno besedilo