When polymer molecules pass near the hyperbolic point of a microchannel cross flow, they are strongly stretched. As the strain rate is varied at low Reynolds number (< 10(-2)), tracer and particle-tracking experiments show that molecular stretching produces two flow instabilities: one in which the velocity field becomes strongly asymmetric, and a second in which it fluctuates nonperiodically in...

The technological objectives of this project are to investigate the mechanics of wave-driven flow on complex topographies. Specifically, we are examining the occurrence, forms, and detailed causes of flow instabilities over complex topographies; the influence of three dimensional topographical features on large scale flow features, the forms and utility of simplified expressions in predicting f...

The formation of internal transport barriers (ITBs) is investigated in MAST spherical tokamak (ST) plasmas. The roles of E×B flow shear, q-profile (magnetic shear) and MHD activity in their formation and evolution are studied using data from high-resolution kineticand q-profile diagnostics. In L-mode plasmas, with co-current directed NBI heating, ITBs in the momentum and ion thermal channels fo...

We carry out an analysis of the stability of a liquid jet into a gas or another liquid using viscous potential flow. The instability may be driven by Kelvin–Helmholtz KH instability due to a velocity difference and a neckdown due to capillary instability. Viscous potential flow is the potential flow solution of Navier–Stokes equations; the viscosity enters at the interface. KH instability is in...

BACKGROUND AND PURPOSE Recent high-resolution computational fluid dynamics studies have uncovered the presence of laminar flow instabilities and possible transitional or turbulent flow in some intracranial aneurysms. The purpose of this study was to elucidate requirements for computational fluid dynamics to detect these complex flows, and, in particular, to discriminate the impact of solver num...

We propose a hydrodynamic mechanism, based on the Marangoni flow, to describe growth instabilities of liquid-condensed islands in the supercooled liquid-expanded phase of two-dimensional Langmuir monolayers. This Marangoni instability is intrinsic to Langmuir monolayers and is not controlled by the expulsion of chemical impurities from the liquid-condensed phase. The hydrodynamic transport of t...

We investigate the stability of relativistic jets using three-dimensional hydrodynamic simulations. The propagation of relativistic flow that is continuously injected from the boundary of computational domain into a uniform ambient medium is solved. An intriguing finding in our study is that Rayleigh-Taylor and Richtmyer-Meshkov type instabilities grow at the interface between the jet and surro...

The symmetry breaking of the actin network from radial to longitudinal symmetry has been identified as the major mechanism for keratocytes (fish cells) motility on solid substrate. For strong friction coefficient, the two dimensional actin flow which includes the polymerisation at the edge and depolymerisation in the bulk can be modelled as a Darcy flow, the cell shape and dynamics being then m...

Abstract A phenomenological model of parametric surface waves (Faraday waves) is introduced in the limit of small viscous dissipation that accounts for the coupling between surface motion and slowly varying streaming and large scale flows (mean flow). The primary bifurcation of the model is to a set of standing waves (stripes, given the functional form of the model nonlinearities chosen here). ...

A three-dimensional (3-D) modal analysis of an excited circular jet with Reynolds number of 9500 is conducted using proper orthogonal decomposition (POD) and a highspeed 3-D flow visualization system. Large sets of 3-D data are acquired in the near field before the end of the potential core and the transition region of the jet. POD is used to objectively characterize and classify the 3-D images...