Modeling Low Reynolds Number Flows Driven by Forward-Propagating and Reflected Boundary Waves in Concentric Micro-Cylinders

We report on a computational model used to study the reversal of flow direction inside the annular region between concentric micro-cylinders filled with an incompressible Newtonian fluid. The flow is induced by boundary deformations on the inner and outer cylinder surfaces due to forward-propagating transverse waves and their reflections. This microfluidic transport mechanism is postulated as a vital pathway for removal of beta-amyloid from the brain along sub-millimeter cerebral arteries, and failure of this clearance is associated with Alzheimer’s disease. We show that the direction of this annular flow depends on superposition of the peristaltic waves and their reflection waves. A control volume analysis is developed to predict the transport characteristics and compared with numerical solutions of the Navier-Stokes equations. The identified set of microfluidic parameters that leads to a net reverse flow will aid biologists in understanding why an aging brain becomes prone to beta-amyloid accumulation.