Motivated by recent experiments on the electro-hydrodynamic instability of spincast polymer films, we study the undulation instability of a thin viscoelastic polymer film under in-plane stress and in the presence of either a close by contactor or an electric field, both inducing a normal stress on the film surface. We find that the in-plane stress affects both the typical timescale of the insta...

The linear normal-mode stratorotational instability (SRI) is analytically reexamined in the in-viscid limit where the length scales of horizontal disturbances are large compared their vertical and radial counterparts. Boundary conditions different than channel walls are also considered. This quasi-hydrostatic, semi-geostrophic (QHSG) approximation allows one to examine the effect of a verticall...

A granular instability is studied experimentally and numerically as a packing of dense granular material positioned above a gap of air falls under gravity in a closed Hele-Shaw cell; a granular analog of the RayleighTaylor instability. A characteristic pattern of fingers separated by dilute bubbles emerges along the interface, and, in contrast to the classical, hydrodynamic instability, a trans...

Magnetic fields can be created in stably stratified (non-convective) layers in a differentially rotating star. A magnetic instability in the toroidal field (wound up by differential rotation) replaces the role of convection in closing the field amplification loop. Tayler instability is likely to be the most relevant magnetic instability. A dynamo model is developed from these ingredients, and a...

Submitted for the DFD11 Meeting of The American Physical Society Hydrodynamic instability induced by a precipitation reaction in a Hele-Shaw cell YUKI ISHII, YUICHIRO NAGATSU, Nagoya Institute of Technology, 466-8555, Japan, ANNE DE WIT, Nonlinear Physical Chemistry Unit, CP 231, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium — We experimentally demonstrate hydrodynamic fingering d...

Motivated by the large effect of turbulent drag reduction by minute concentrations of polymers, we study the effects of a weakly space-dependent viscosity on the stability of hydrodynamic flows. In a recent paper [Phys. Rev. Lett. 87, 174501, (2001)], we exposed the crucial role played by a localized region where the energy of fluctuations is produced by interactions with the mean flow (the "cr...

When a fluid is displaced by a less viscous one in a porous medium, a hydrodynamic instability appears leading to the formation of some kind of fingers of the upstream fluid invading the downstream one, hence the name "viscous fingering" (VF) given to this instability. In a LC column, such an instability is likely to appear at that of the two interfaces between the sample and the eluent which e...