Swirling flows with applications to energy and biology

Abstract

This thesis explores the dynamics of flows with secondary swirling motions in a variety of systems using experiments, theoretical techniques, and direct numerical simulations of the Navier-Stokes equations. The applications of this work include: (a) modeling flows in piping networks such as in systems of curved pipes or downstream of perturbations, (b) enhancing or eliminating a novel particle-capture mechanism in branching flows as well as capturing biomaterials and visualizing their shear-induced interactions, and (c) modeling the enhanced diffusiophoretic motion of suspended particles in one-dimensional solute gradients.

The first part of this dissertation begins with a discussion of the downstream decay of fully developed flow in a curved pipe that exits into a straight outlet. Scaling arguments are developed, numerical simulations are used to quantify transition lengths, and an analogy is made to the flow in the downstream outlets of a T-junction flow. Later, these scaling arguments are extended to analytical solutions for the flow downstream of a weakly curved pipe at large Reynolds numbers. By appropriate linearizations of the Navier-Stokes equations in both cylindrical and toroidal coordinates, the developing flow in the entry region of a weakly curved pipe is shown to have the same analytical solution as the flow downstream of a curved pipe. Using a similar analytical approach, the flow in a cylindrical, straight pipe downstream of an arbitrary 3D perturbation is solved for both the Stokes flow and high-Reynolds-number limits.

The second part of this dissertation identifies unique features and applications of the flow in a branching junction. Specifically, a flow-induced, Reynolds-number-dependent particle-capture mechanism is shown to originate from features resembling classical vortex breakdown. By varying the junction angle and Reynolds number, I show how this particle capture mechanism can be enhanced or eliminated, and I show how the recirculation regions responsible for capture originate and evolve. I utilize this capture phenomenon to produce giant unilamellar vesicles through shear-induced fusion, and demonstrate a platform for visualizing shear-induced biomaterial interactions in flow. In the final part of this dissertation, the diffusiophoretic motion of suspended colloidal particles under 1D solute gradients is solved using numerical and analytical techniques.