Unsteady concentration transport over an array of cylinders in low-Reynolds-number flow

Abstract

The transport mechanism of concentration over an array of cylinders is investigated numerically for a transient low-Reynolds-number flow (Re = 1). This study is motivated by the olfactory sensing of antennules and their bio-inspired applications to chemical sensors. Two types of arrays, a single column of three cylinders and a square array of three by three cylinders, are used as simplified models for collecting concentration, and geometrical parameters such as gap size between the cylinders and initial distance between a concentration patch and the cylinder array are considered to evaluate how they change the concentration flux into the cylinders. The cumulative concentration flux of the array and the spatial distribution of concentration on the surface of the cylinder are compared between low and high Péclet numbers, Pe = 1 and 1000. For the low Péclet number, the flux efficiency is negatively affected by small gaps between the cylinders because the incoming concentration patch detours around the array due to hydrodynamic blockage in the gaps. By contrast, for the high Péclet number, the concentration flux benefits from entrapment of the patch over an extended period inside the array with narrow gaps, and thus, the flux efficiency can be superior to that of a single isolated cylinder. The flux efficiency of the array is in the inverse relationship with the initial distance of the patch from the cylinder array, and the high Péclet number exhibits a more notable drop in the flux efficiency with an increase in initial distance.