Chemosensory guidance cues in a turbulent chemical odor plume

The characteristics of chemical odor plumes released into a turbulent open channel flow are evaluated in the context of chemical plume tracking. The o bjective is to assess the availability and usefulness of chemosensory cues to animals, such as benthic crustaceans, attempting to orient in the plume. Releasing fluorescent dye into the fully developed turbulent boundary laye r of a large laboratory-scale flume created turbulent odor plumes. Flow vis ualization of odor fields created with varying release velocity, release di stance from the bed, and nozzle diameter indicated that chemosensory cues i n plumes depend on the release characteristics as well as the ambient flow conditions. Thus, to understand animal behavior, it is important to quantif y the plume release properties and characteristics. We chose to quantify co ncentration fields for the case of isokinetic release using the planar lase r-induced fluorescence technique. These measurements indicate that the time -averaged concentration converges far too slowly to be useful to a foraging animal. Similarly, resolving the rise slope of a concentration burst requi res sampling rates unattainable by animals, and the spatial variation of ri se slope is too mild to follow without lengthy sampling periods. In additio n, only mild variation with distance from the source is observed in the con centration burst magnitude and duration. Thus, the time-averaged concentrat ion, rise slope, and burst shape all appear to have limited usefulness for plume orientation for animals known to orient effectively to these types of odor sources.