1. On new approach to rheological modeling of an electrostatic ash and water - quadratic lawPrimož Ternik, 2002, objavljeni znanstveni prispevek na konferenci 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 v DKUM: 01.06.2012; Ogledov: 2031; Prenosov: 43 Povezava na celotno besedilo |
2. |
3. Symmetry breaking phenomena of purely viscous shear-thinning fluid flow in a locally constricted channelPrimož Ternik, 2008, izvirni znanstveni članek Opis: The goal of a present study is to investigate the effects of generalized Newtonian fluids on the threshold of the transition from flow symmetry to its asymmetry for the flow through a locally constricted channel. We consider purely viscous shear-thinning fluid and compare it with the Newtonian fluid. Fluid flow is studied numerically by solving the two dimensional momentum equations along with the continuity equation and the Carreau-Yasuda rheological model. We report systematic results in a range of generalized Reynolds number 250▫$leq$▫Re▫$leq$▫150 with a focus on its critical value. Results indicate that the shear-thinning viscous behaviour decreases the onset of bifurcation phenomena and the critical value of Reynolds number. Last but not least, a systematic grid refinement analysis and numerical accuracy study is performed and present numerical results may be treated as the benchmark. Ključne besede: bifurcation, inelastic shear-thinning fluid, Carreau-Yasuda model, numerical modelling Objavljeno v DKUM: 31.05.2012; Ogledov: 1574; Prenosov: 127 Povezava na celotno besedilo |
4. Non-Newtonian fluid flow through a planar symmetric expansion: shear thickenning fluidsPrimož Ternik, Jure Marn, Zoran Žunič, 2006, izvirni znanstveni članek 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 v DKUM: 31.05.2012; Ogledov: 1581; Prenosov: 56 Povezava na celotno besedilo |
5. Laminar flow of a shear-thickening fluid in a 90° pipe bendJure Marn, Primož Ternik, 2006, izvirni znanstveni članek Opis: The non-Newtonian fluid flow in a sharp 90 curved pipe is studied numerically to obtain the pressure loss coefficient prompted by disagreement between the existing empirical correlations and results obtained by computer codes. This disagreement results from presumption of fully developed flow throughout the curvature (correlations) while the actual flow is partially developed for the Newtonian and sharp 90 curved bend non-Newtonian flows, and fully developed for slightly bent 90 curvature non-Newtonian flow. The Quadratic model is employed to accommodate the shear-thickening behavior of an electrostatic ash and water mixture. Numerical results are obtained for different values of Reynolds number. Finally, results for local pressure loss coefficient are compared with values obtained for the Power law rheological model. Ključne besede: shear-thickening fluid, fluid dynamics, rheological model, pipe bend flow, numerical modelling, pressure losses Objavljeno v DKUM: 30.05.2012; Ogledov: 1689; Prenosov: 82 Povezava na celotno besedilo |