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RISS 인기검색어
- 검색키워드
- 저자 : Atalik, (검색결과 4 건)
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Isothermal and non-isothermal viscoelastic flow of PTT fluid in lid-driven polar cavity
Mercan, Hatice,Atalik, Kunt 한국유변학회 2012 Korea-Australia rheology journal Vol.24 No.4
The isothermal and non-isothermal viscoelastic flow of Phan-Thien-Tanner (PTT) fluids is considered in lid-driven polar cavity geometry, using a numerical solution method with parameter continuation technique. Thermoelastic effects, in terms of elastic/elongational effects and viscous dissipation, are demonstrated by the changes in vortical structure, temperature/stress distributions and heat transfer characteristics in the curved cavity. Central vortex/maximum temperature location shifts are observed under elastic and elongational (strain hardening and strain softening/shear thinning) effects for isothermal and non-isothermal conditions. The growth in size and strength of a secondary vortex is denoted in the downstream stationary corner of the cavity for the viscoelastic fluid under strain hardening, which also introduces an increase in stress gradients. Viscous heating is observed with elongational effects near the central vortex in the cavity. Stress components and their gradients decrease under viscous dissipation. The changes in temperature field and heat transfer properties in the cavity are revealed.
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Flow structure for Power-Law fluids in lid-driven arc-shape cavities
Mercan, Hatice,Atalik, Kunt 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.2
In this paper the lid-driven flow of a Power-Law fluid in arc-shape cavities is studied. Two different arc cavity cross sections are considered with arc angle ratios r=1/2 and r=1/3. The unsteady stream-function-vorticity formulation is adopted together with a Power-Law constitutive relation. Body-fitted coordinate transformation is applied to generate orthogonal computational grids. The equations are discretized in space using a second order finite difference numerical method. Time integration is performed using fourth order Runge-Kutta explicit scheme. The combined effects of inertia, shear thinning/shear thickening and curved geometry on the vortical structure and velocity profiles are shown. The results are compared to Newtonian fluid case. It is found that under inertia, shear thinning effects lead to the early formation and growth of secondary vortices in the curved cavity, however shear thickening has an opposite effect.
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Flow structure for Power-Law fluids in lid-driven arc-shape cavities
Hatice Mercan,Kunt Atalik 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.2
In this paper the lid-driven flow of a Power-Law fluid in arc-shape cavities is studied. Two different arc cavity cross sections are considered with arc angle ratios r=1/2 and r=1/3. The unsteady streamfunction-vorticity formulation is adopted together with a Power-Law constitutive relation. Body-fitted coordinate transformation is applied to generate orthogonal computational grids. The equations are discretized in space using a second order finite difference numerical method. Time integration is performed using fourth order Runge-Kutta explicit scheme. The combined effects of inertia, shear thinning/shear thickening and curved geometry on the vortical structure and velocity profiles are shown. The results are compared to Newtonian fluid case. It is found that under inertia, shear thinning effects lead to the early formation and growth of secondary vortices in the curved cavity, however shear thickening has an opposite effect.
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Rotating-surface-driven non-Newtonian flow in a cylindrical enclosure
Yalin Kaptan,Ali Ecder,Kunt Atalik 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.4
The numerical simulations of non-Newtonian flows become difficult as the Weissenberg number increases. The main objective of this study is to generate a robust and efficient matrix-free Inexact Newton-Krylov solver (IN-GMRES) which can deal with the high nonlinearities arising from the increased Weissenberg numbers. In order to achieve this aim, non-Newtonian flows of rotating surface driven cylindrical enclosure problem is numerically investigated by using three differential viscoelastic constitutive relations namely Upper Convected Maxwell (UCM), Oldroyd B and Giesekus. The results obtained by IN-GMRES solver are validated and compared with the POLYFLOW simulations. Additionally, the selection of the constitutive relation, effects of the Weissenberg number and effects of the Reynolds number are studied. The simulations indicate that the generated algorithm is capable of solving higher Weissenberg number problems (up to the Elasticity number limit of 130) when compared to the previous studies. Furthermore, it is shown that with the increasing Weissenberg number, the reversed flow can be observed in the flow domain and in some cases, depending on the Reynolds number, re-formation of the Newtonian like flow is possible at high Weissenberg numbers.
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