Chemosensory guidance cues in a turbulent chemical odor plume

Webster, D. R., M. J. Weissburg

Limnol. Oceanogr., 46(5), 2001, 1034-1047 | DOI: 10.4319/lo.2001.46.5.1034

ABSTRACT: The characteristics of chemical odor plumes released into a turbulent open channel flow are evaluated in the context of chemical plume tracking. The objective 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 layer of a large laboratory-scale flume created turbulent odor plumes. Flow visualization of odor fields created with varying release velocity, release distance from the bed, and nozzle diameter indicated that chemosensory cues in plumes depend on the release characteristics as well as the ambient flow conditions. Thus, to understand animal behavior, it is important to quantify the plume release properties and characteristics. We chose to quantify concentration fields for the case of isokinetic release using the planar laser-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 requires sampling rates unattainable by animals, and the spatial variation of rise slope is too mild to follow without lengthy sampling periods. In addition, only mild variation with distance from the source is observed in the concentration burst magnitude and duration. Thus, the time-averaged concentration, 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.

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