Structures in smells: Coupling fluid dynamic cues to odor signals in olfactory landscapes

Animals exploit olfactory cues for survival, requiring navigation of complex odor plumes in diverse environments. As organisms navigate, they encounter a rich set of fluid dynamic cues (e.g. accelerations, strains, vorticity) alongside odor cues, owing to the coupling of the Navier-Stokes and Advection-Diffusion equations. Lagrangian coherent structures (LCS) provide an intuitive framework for investigating coupled flow and odor structure; they are derived from the flow deformation field and have been shown to drive the spatial organization and temporal evolution of scalar fields in chaotic flows. We investigate this coupled structure using 2D numerical simulations of chaotic plume dispersion with passive scalars released downstream of an array of interacting cylinder wakes. We use event-based statistics centered on whiff occurrences to quantify relative timing between flow and odor cues across plume regions and candidate flow cues. We find significant differences in relative timing across plume regions, and provide a physical interpretation based on the LCS framework and considerations of local mixing regimes. Spatial structure in relative timing variations between flow and odor cues could inform fundamental olfactory search tasks like edge detection or source localization.