Evan Dare

Student: Evan Dare

Project: Torque and Force-Free Swimming at Low Reynolds Number

Poster: Horizontal (PDF) | Vertical (PDF)

Institution: Lehigh University

Major: Mechanical Engineering

Advisor: Ebru Demir

Abstract

Artificial bacteria are strong candidates to achieve biomedical applications such as drug delivery and minimally invasive surgery. Analytical solutions for the swimming velocity of the force and torque free swimming of bacterium with a helical tail already exist in literature, however, they neglect the hydrodynamic interactions and are valid only for Newtonian fluid. In this numerical study, we begin with solving 3D Navier-Stokes equations to explore the effect of hydrodynamic interactions on swimming performance. Our results agree with the analytical solutions at the limit of zero head size, however, for finite Rhead/Rtail we found that the analytical solution overpredicted the speed of the bacterium. Next, we investigate bacterial swimming in shear-thinning fluids using the Carreau fluid model, which captures the non-Newtonian behavior of bodily fluids very well. We validate the results of our shear-thinning simulations at the Newtonian limit against the Newtonian results. We observed both enhanced and reduced swimming velocities of the bacterium in shear-thinning fluid compared to Newtonian swimming depending on Rhead/Rtail and the nondimensional Carreau Number. Ultimately, swimming velocity manifests as a function of Rhead/Rtail and Carreau Number for a fixed model helical tail, which suggests that the artificial bacterium design and actuation can be optimized to achieve a desired swimming behavior.