The External Aerodynamics of Canine Olfaction

Abstract

Following a review of precedent literature, flow visualization techniques are used to observe external canine olfactory airflows. This reveals the canine nostril as a variable-geometry aerodynamic sampler, being alternately a potential-flow inlet during inspiration and an outlet flow diverter during expiration. Close nostril proximity to a scent source is important. Separate flow pathways are provided for the inspired and expired air by way of nostril flexure. During sniffing, the nostril midlateral slits open to direct the expired air rearward and to the sides, away from the object being scented. If particulates are present on a surface being scented, they are readily disturbed by these expired jets and can be subsequently inspired. These and other results are brought to bear upon aerodynamic sampling for purposes of chemosensing, in which a sampler or sniffer acquires the airborne trace signal and presents it to an appropriate detector. Preliminary results from a laboratory-prototype sniffer are given.