Small‐scale fluid dynamics of olfactory antennae

Abstract

A critical step in the process of olfaction is the arrival at the surface of a chemosensory structure of chemical signals from the environment. Many organisms use appendages bearing arrays of microscopic hairs to pick up chemical signals from the surrounding water or air. In this study a general model of fluid flow between neighboring hairs in an array is used to explore the effects of hair size, spacing, and speed on flow near olfactory hairs. If an array of hairs is moved more rapidly: 1) the volume flow rate through it rises, causing higher molecule encounter rates even though a smaller proportion of the odorants passing through the array have time to diffuse to hair surfaces, and 2) velocity gradients along hair surfaces become steeper, causing greater sensitivity to changes in odorant concentration. The more closely‐spaced the hairs, the less sensitive they are to these effects of changing speed.