Rational design with inertia: particle migration and hairy surfaces
Friday, April 20, 2018
Nonlinearity, such as inertia in the Navier-Stokes equations, makes rational design of devices difficult. In this talk, we will examine the role of inertia in two different of hydraulic devices with the goal of improving the design of devices. In both cases, we are interested in flows at Reynolds number between 1 and 100, where inertial stresses are equally or more than dominant over viscous stresses. First, we consider particle inertial migration in microfluidic devices. Particles suspended in inertial flow through a rectangular channel will migrate across streamlines and focus to one of finitely many inertial focusing streamlines. We develop a mixed asymptotic-numerical theory for determining where the particles focus based on particle size and initial starting point. We verify this theory against experimental data using a novel particle tracking and reconstruction algorithm. Once particles are inertially focused to a single streamline, the particles interact with each other and form regularly spaced trains of particles. We show that inertia plays in unintuitive role in the formation of these particle trains. Second, we consider the inertial flow around a rigid bed of hairs. Biologists have observed that crustaceans manipulate the Reynolds number of the flow between their chemosensory hairs in order to optimize their ability to sense and track food. In order to rationally design biomimetic devices, we need to understand how the flow depends on inertia and the various size parameters of the system. We will show a theoretical prediction for the design of devices and verify it against preliminary experimental data.