SMALL-SCALE FLUID-DYNAMICS OF OLFACTORY ANTENNAE

A critical step in the process of olfaction is the arrival at the surf ace of a chemosensory structure of chemical signals from the environme nt. Many organisms use appendages bearing arrays of microscopic hairs to pickup chemical signals from the surrounding water or air. In this study a general model of fluid flow between neighboring hairs in an ar ray 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 dow rate through it rises, causing higher molecule enc ounter rates even though a smaller proportion of the odorants passing through the array have time to diffuse to hair surfaces, and 2) veloci ty gradients along hair surfaces become steeper, causing greater sensi tivity to changes in odorant concentration. The more closely-spaced th e hairs, the less sensitive they are to these effects of changing spee d.