“…These equations are very similar to those for Couette flow of a UCM fluid [5]. In fact, the only difference is in the coefficient of the highest derivative, and the final term in Eqs.…”
mentioning
confidence: 58%
“…In steady, simple shear it gives a viscosity G M ( and first normal stress difference G M ( 2 2 . If ( is constant, we recover the UCM model whose stability characteristics are well known [5], and this will provide a useful check on our computations. To explore shear-thinning possibilities we put…”
We consider the inertialess planar channel flow of a White±Metzner (WM) fluid having a power-law viscosity with exponent n. The case n 1 corresponds to an upper-convected Maxwell (UCM) fluid. We explore the linear stability of such a flow to perturbations of wavelength k À1 . We find numerically that if n < n c % 0.3 there is an instability to disturbances having wavelength comparable with the channel width. For n close to n c , this is the only unstable disturbance. For even smaller n, several unstable modes appear, and very short waves become unstable and have the largest growth rate. If n exceeds n c , all disturbances are linearly stable. We consider asymptotically both the long-wave limit which is stable for all n, and the shortwave limit for which waves grow or decay at a finite rate independent of k for each n.The mechanism of this elastic shear-thinning instability is discussed. #
“…These equations are very similar to those for Couette flow of a UCM fluid [5]. In fact, the only difference is in the coefficient of the highest derivative, and the final term in Eqs.…”
mentioning
confidence: 58%
“…In steady, simple shear it gives a viscosity G M ( and first normal stress difference G M ( 2 2 . If ( is constant, we recover the UCM model whose stability characteristics are well known [5], and this will provide a useful check on our computations. To explore shear-thinning possibilities we put…”
We consider the inertialess planar channel flow of a White±Metzner (WM) fluid having a power-law viscosity with exponent n. The case n 1 corresponds to an upper-convected Maxwell (UCM) fluid. We explore the linear stability of such a flow to perturbations of wavelength k À1 . We find numerically that if n < n c % 0.3 there is an instability to disturbances having wavelength comparable with the channel width. For n close to n c , this is the only unstable disturbance. For even smaller n, several unstable modes appear, and very short waves become unstable and have the largest growth rate. If n exceeds n c , all disturbances are linearly stable. We consider asymptotically both the long-wave limit which is stable for all n, and the shortwave limit for which waves grow or decay at a finite rate independent of k for each n.The mechanism of this elastic shear-thinning instability is discussed. #
“…The eigenvalues from this group are "purely elastic" in the sense that they exist even in the limit Re = 0. The pair was discovered by Gorodtsov and Leonov (Gorodtsov and Leonov, 1967) for twodimensional purely elastic plane Couette flow and can be generalized to the 3-dimensional case:…”
Section: Resultsmentioning
confidence: 96%
“…The only results available are on the linear stability of these flows. For essentially all studied visco-elastic models, laminar plane Couette flow is linearly stable (Gorodtsov and Leonov, 1967, Renardy and Renardy, 1986, Renardy, 1992, Wilson et al, 1999 (note the exception (Grillet et al, 2002)). In the case of pipe flow, the linear stability was demonstrated numerically by Ho and Denn (Ho and Denn, 1978) for any value of the Weissenberg and Reynolds numbers.…”
A non-linear stability analysis of plane Couette flow of the Upper-Convected Maxwell model is performed. The amplitude equation describing time-evolution of a finite-size perturbation is derived. It is shown that above the critical Weissenberg number, a perturbation in the form of an eigenfunction of the linearized equations of motion becomes subcritically unstable, and the threshold value for the amplitude of the perturbation decreases as the Weissenberg number increases.
“…After substituting the Fourier modes for stress and velocity into Eqs. 1, 2 and 4, the subsequent equations can be reduced to a single equation in v z (n) (z) which has a general solution given by (GORODTSOV and LEONOV, 1967;SHANKAR and KUMAR, 2004) …”
Section: Small Perturbations To a Flat Fault Interfacementioning
Abstract-High resolution topography measurements of the Vuache-Sillingy fault (Alps, France) reveal a characteristic roughness of the fault zone. We investigate the effect of roughness on the rheology of a planar shear configuration by using a model system consisting of a visco-elastic layer embedded into a rigid solid. The model is discussed in the context of several geological cases: a damage fault zone, a fault smeared with a clay layer, and a shear zone with strain weakening. Using both analytical approaches and finite element simulations, we calculate to linear order the relation between wall roughness and the viscous dissipation in the fault zone as well as the average shear rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.