The dilute-to-dense transition of granular flow of particle size d(0) is studied experimentally in a two-dimensional channel (width D) with confined exit (width d). Our results show that with fixed d and D there is a maximum inflow rate Q(c) above which the flow changes from dilute to dense and the outflow rate drops abruptly from Q(c) to a dense rate Q(d). A rescaled critical rate q(c) ...

This paper numerically investigates the magnetohydrodynamic equations in three dimensions with periodic boundary conditions in a parameter range where a forced fluid flow is chaotic. It is found that the transition to dynamo action, whereby the magnetic field is sustained by interaction with the forced flow, is a blowout bifurcation. The blowout bifurcation is typified by bursting behavior, or ...

The flow of fluid past a cylinder has been widely studied both analytically and numerically, and provides insight to the behavior of flow given different fluid properties. Particularly interesting is the transition from steady flow to vortex shedding in the wake of the cylinder. This behavior is dependent on several parameters, but most importantly, the Reynolds number (Re), which is a dimensio...

release during PIPAAm collapse. This burst is analogous to drug release from collapsing PIPAAm gel disks undergoing analogous thermal treatment. Similarly, just after each temperature return to 30 °C, small fluores-cent spikes are observed. In contrast, oscillatory fluorescent changes have been observed using 0.5 min cyclic intervals (shown in Fig. 3c) indicating subtle PIPAAm swell–shrink tran...

Roughness effects on lubricant flows are investigated via 2D lattice Boltzmann simulations. At a Reynolds numbers of order 1000 a transition from laminar to unsteady flow is observed by an increase of the roughness height from about 10% to about 25% of the channel width. At lower Reynolds numbers (where the flow is laminar in both channels), the transition is observed when increasing the wall r...

Tank-treading, tumbling, and trembling are different types of the vesicle behavior in an external flow. We derive a dynamical equation enabling us to establish a state of nearly spherical vesicles. For a 2D external flow, the character of the vesicle dynamics is determined by two dimensionless parameters, depending on the vesicle excess area, fluid viscosities, membrane viscosity and bending mo...

The understanding of transition in shear flows has recently progressed along new paradigms based on the central role of coherent flow structures and their nonlinear interactions. We follow such paradigms to identify, by means of a nonlinear optimization of the energy growth at short time, the initial perturbation which most easily induces transition in a boundary layer. Moreover, a bisection pr...