Phase structure during capillary displacement of fluid phases within rough-walled fractures is controlled by the competition between random aperture variability which tends to roughen the interface and in-plane curvature which tends to smooth it. We show that the phase structure and corresponding areal saturation at the end of displacement depend primarily on the ratio of two dimensionless para...

We present an experimental study of the aspect-ratio dependence of two-phase displacement flows in channels of rectangular cross section. Above a buoyancy-dependent threshold Ca[over ;]_{t}, we find that the bulk features of the flow depend only on a modified capillary number Ca[over ;]=[1+0.12(alpha-1)+0.018(alpha-1);{2}]Ca, where Ca is the unmodified capillary number and alpha is the aspect r...

The immiscible displacement of a wetting fluid by a non-wetting one in heterogeneous porous media is modeled by using a multi-scale network-type analysis: (1) The pressure-controlled immiscible displacement of water by oil in pore-and-throat networks (length scale~1mm) is controlled by capillary forces. (2) The pressure-controlled immiscible displacement in uncorrelated or spatially correlated ...

Single-phase flows of viscoelastic polymer solutions in both microfluidic devices and rock cores exhibit apparent flow thickening. We demonstrate that this thickening occurs above a critical Deborah number corresponding to the onset of spatio-temporal fluctuations. These fluctuations are observed to occur over a broad range of spatial and temporal scales consistent with elastic turbulence. The ...

A complete identification and characterization of three distinct capillary instabilities in nematic liquid crystal fibers is presented. Linear stability analysis of capillary instabilities in thin nematic liquid crystalline cylindrical fibers is performed by formulating and solving the governing nematocapillary equations. A representative axial nematic orientation texture is studied. The surfac...

We have investigated experimentally the competition between viscous, capillary, and gravity forces during drainage in a two-dimensional synthetic porous medium. The displacement of a mixture of glycerol and water by air at constant withdrawal rate has been studied. The setup can be tilted to tune gravity, and pressure is recorded at the outlet of the model. Viscous forces tend to destabilize th...

Chronic increases in arterial blood flow elicit an adaptive response of the arterial wall, leading to vessel enlargement and reduction in wall shear stress to physiological baseline value. Release of nitric oxide from endothelial cells exposed to excessive shear is a fundamental step in the remodeling process, and potentially triggers a cascade of events, including growth factor induction and m...

Introduction To enhance slower arterial flow as well as faster flow without increasing imaging time, we have proposed a new MRA technique named hybrid of opposite-contrast MRA (HOP-MRA) that combined standard TOF white-blood (WB) MRA with the flow-sensitive black-blood (FSBB) sequence, resulting in excellent visualization of slow-flow vessels, as compared to the MTC-TOF MRA technique [1,2]. How...

Flow fractionation of cells using physical fields to achieve lateral displacement finds wide applications, but its extension to surface molecule-specific separation requires labeling. Here we demonstrate affinity flow fractionation (AFF) where weak, short-range interactions with asymmetric molecular patterns laterally displace cells in a continuous, label-free process. We show that AFF can dire...