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Weakly nonlinear stability analysis of a flow past a neo-Hookean solidat arbitrary Reynolds numbers

Chokshi, Paresh and Kumaran, V (2008) Weakly nonlinear stability analysis of a flow past a neo-Hookean solidat arbitrary Reynolds numbers. In: Physics of Fluids, 20 (9). 094109-1.

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The finite amplitude stability of a plane Couette flow over a deformable solid medium is analyzed with emphasis on the class of high Reynolds number (Re) modes, referred to as the wall modes, for which the viscous stresses are confined to a thin layer adjacent to the fluid-solid interface with thickness O (Re-1/3) times the channel width in the limit Re >> 1. Here, the Reynolds number is defined in terms of the top plate velocity V and the channel width R. Previous linear stability analyses have shown that the wall modes are unstable for Newtonian flow past a linear viscoelastic solid. In the present study, the analysis is extended to examine the weakly nonlinear stability of these unstable wall modes in order to determine the nature of bifurcation of the transition point to finite amplitude states. To account for the finite strain deformations, the flexible solid medium is described by a neo-Hookean elastic model which is a generalization of the commonly used linear constitutive model. The linear stability analysis provides the critical shear rate Gamma(c) and the critical wavenumber in the axial direction alpha(c), where the dimensionless shear rate is defined as Gamma = root rho V-2/G, where rho is the fluid density and G is the shear modulus of the elastic solid. The critical parameter Gamma(c) for the neo-Hookean solid is found to be close to Gamma(c) for the linear elastic solid analyzed in the previous studies. The first Landau constant s((1)), which is the finite amplitude correction to the linear growth rate, is evaluated in the weakly nonlinear stability analysis using both the numerical technique and the high Re asymptotic analysis. The real part of the Landau constant, s(r)((1)), is negative for the wall mode instability in the limit Re >> 1 for a wide range of dimensionless solid thickness H, indicating that there is a supercritical bifurcation of the wall mode instability. The amplitude of the supercritically bifurcated equilibrium state is derived in the vicinity of the critical point. The equilibrium amplitude, in the form A(1e)(2)/(Gamma-Gamma(c)), is found to scale as Re-(1/3) in the limit Re >> 1 and is proportional to H-2.3 for H >> 1 in the same limit

Item Type: Journal Article
Publication: Physics of Fluids
Publisher: American Institute of Physics
Additional Information: Copyright of this article belongs to American Institute of Physics
Keywords: channel flow;Couette flow;flow instability;shear modulus.
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 23 Mar 2009 05:58
Last Modified: 19 Sep 2010 04:52
URI: http://eprints.iisc.ac.in/id/eprint/16486

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