DOWNSTREAM INSTABILITY OF VISCOELASTIC FLOW PAST A CYLINDER

Document Type : Original Article

Authors

1 Egyptian Armed Forces+

2 Laboratoire de Mécanique de Lille, UMR-CNRS 8107 Université des Sciences et Technologies de Lille, Polytech’Lille - Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France

3 Laboratoire de Mécanique de Lille, UMR-CNRS 8107 Université des Sciences et Technologies de Lille, Polytech’Lille - Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France.

4 Laboratoire de Mécanique de Lille, UMR-CNRS 8107 Université des Sciences et Technologies de Lille, Polytech’Lille - Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France..

Abstract

This work aims at simulating two-dimensional viscoelastic incompressible fluid flow past a non-confined cylinder. The finite volume method is used to descritize the governing equations written in the generalized orthogonal coordinate system. For the viscoelastic constitutive equation, two models are studied; the Oldryod-B model and the Phan-Thien-Tanner model PTT model. The quadratic scheme QUICK is employed to evaluate the convection terms. The terms of diffusion, advection and
acceleration are treated explicitly. The Elastic Viscous Split Stresses (EVSS) scheme is used to decompose the stress tensor to enhance the stability of computations. The obtained results indicate that, for Newtonian flow, the onset of von Karman street occurs at Reynolds number Re ≥ 47. Upon the onset of vortex shedding the downstream instability zone is elongated and the shedding frequency is reduced. The PTT model proves more stability of computations and reached higher Deborah numbers.

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