arXiv subjects

Kyle A. Baldwin

Publications and source records attributed to Kyle A. Baldwin.

3 recordsLinked to original sources

arXiv2019

Topological Stabilization and Dynamics of Self-propelling Nematic Shells

Liquid shells (e.g. double emulsions, vesicles etc.) are susceptible to interfacial instability and rupturing when driven out of mechanical equilibrium. This poses a significant challenge for the design of liquid shell based micro-machines, where the goal is to maintain stability and dynamical control in combination with motility. Here we present our solution to this problem with controllable self-propelling liquid shells, which we have stabilized using the soft topological constraints imposed by a nematogen oil. We demonstrate, through experiments and simulations, that anisotropic elasticity can counterbalance the destabilizing effect of viscous drag induced by shell motility, and inhibit rupturing. We analyze their propulsion dynamics, and identify a peculiar meandering behavior driven by a combination of topological and chemical spontaneously broken symmetries. Based on our understanding of these symmetry breaking mechanisms, we provide routes to control shell motion via topology, chemical signaling and hydrodynamic interactions.

cond-mat.soft↗

arXiv2016

Propulsion of a two-sphere swimmer

We describe experiments and simulations demonstrating the propulsion of a neutrally-buoyant swimmer that consists of a pair of spheres attached by a spring, immersed in a vibrating fluid. The vibration of the fluid induces relative motion of the spheres which, for sufficiently large amplitudes, can lead to motion of the center of mass of the two spheres. We find that the swimming speed obtained from both experiment and simulation agree and collapse onto a single curve if plotted as a function of the streaming Reynolds number, suggesting that the propulsion is related to streaming flows. There appears to be a critical onset value of the streaming Reynolds number for swimming to occur. We observe a change in the streaming flows as the Reynolds number increases, from that generated by two independent oscillating spheres to a collective flow pattern around the swimmer as a whole. The mechanism for swimming is traced to a strengthening of a jet of fluid in the wake of the swimmer.

physics.flu-dyn↗

arXiv2016

The Rotating Rayleigh-Taylor Instability

The effect of rotation upon the classical two-layer Rayleigh-Taylor instability is considered theoretically and compared with previous experimental results. In particular we consider a two-layer system with an axis of rotation that is perpendicular to the interface between the layers. In general we find that a wave mode's growth rate may be reduced by rotation. We further show that in some cases, unstable axisymmetric wave modes may be stabilized by rotating the system above a critical rotation rate associated with the mode's wavelength, the Atwood number and the flow's aspect ratio. We compare our theory with experiments conducted in a magnetic field using 'heavy' diamagnetic and 'light' paramagnetic fluids and present comparisons between the theoretical predictions and experimental observations.

physics.flu-dyn↗