Stereo inhalation draws ambient fluid into a pair of spatially separated siphons. The ubiquitous mammalian nose morphology of two separated nares uses stereo inhalation to enhance respiration and olfaction. Previous studies have found that stereo inhalation improves the spatial extent of odor capture and success of source localization. However, direct quantification of the spatial extent of inhaled fluid has received less attention, which may provide context for evolutionary adaptations to sensory appendages and design of biologically inspired sniffing devices. We numerically modeled idealized stereo inhalation through a pair of round siphons and evaluated the effects of siphon separation, proximity to boundaries, and inhalation Reynolds number (Re) on the inhaled fluid structure. We find that siphons closer together have approximately three times the lateral perception of sensory information relative to pairs of single siphons. Siphons that protrude above a solid boundary inhale fluid farther away from the orifice relative to siphons flush with the boundary. Additionally, the Reynolds number alters the axial distance that fluid is inhaled from the siphon orifice. As Re decreases from 100 to 1, outward viscous diffusion of suction-driven momentum increasingly dominates its inward advection, enhancing axial biases to inhale fluid more directionally. Organisms may alter morphology (siphon separation and extraction height) and inhalation dynamics (Reynolds number) at behavioral or evolutionary timescales to adapt to their surrounding environments. Our findings can inform principles for engineering applications and provide physical mechanisms that govern sensing enhancements from stereo inhalation.

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• Biological fluid dynamics
• Low Reynolds number flows
• Olfaction