Bridge Radius Evolution during Coalescence of Ferrofluid Droplets Suspended in a Nonmagnetic Outer Fluid.

Understanding the droplet coalescence/merging is vital for many areas of microfluidics such as biochemical reactors, drug delivery, inkjet printing, oil recovery, etc. In the present study, we carried out numerical simulations of two magnetic droplets suspended in a nonmagnetic fluid matrix and coalescing under the influence of an external magnetic field. We observed that the applied magnetic field played a key role in the merging dynamics of the magnetic droplets.

Dynamics of bidensity particle suspensions in a horizontal rotating cylinder.

We report Stokesian dynamics simulations of bidensity suspensions rotating in a horizontal cylinder. We studied the phase space and radial and axial patterns in settling as well as floating systems. Each system was composed of particle mixtures of two different densities.

Fluid flow and particle dynamics inside an evaporating droplet containing live bacteria displaying chemotaxis.

Evaporation-induced particle deposition patterns like coffee rings provide easy visual identification that is beneficial for developing inexpensive and simple diagnostic devices for detecting pathogens. In this study, the effect of chemotaxis on such pattern formation has been realized experimentally in drying droplets of bacterial suspensions. We have investigated the velocity field, concentration profile, and deposition pattern in the evaporating droplet of Escherichia coli suspension in the presence and absence of nutrients.

Stress fluctuations in sheared Stokesian suspensions.

We report an analysis, using the tools of nonlinear dynamics and chaos theory, of the fluctuations in the stress determined from simulations of shear flow of Stokesian suspensions. The simulations are for shear between plane parallel walls of a suspension of rigid identical spheres in a Newtonian fluid, over a range of particle concentration. By analyzing the time series of the stress, we find that the dynamics underlying these fluctuations is deterministic, low-dimensional, and chaotic.