High dynamic range particle image velocimetry analysis of viscous inhalant flows

High dynamic velocity range (DVR) flows are challenging to measure with traditional double-pulse particle image velocimetry (PIV) since no single correlation time scale optimally resolves particle displacements over the entire DVR of interest. Inhalant flows are ubiquitous in engineering and biology and feature a high DVR as they draw viscous fluid through an orifice from a surrounding reservoir since large interior tube velocities rapidly attenuate with exterior distance from the inhalant orifice. We conducted a high-DVR PIV study of viscous inhalant flow hydrodynamics by developing and applying a multi-time-lag type processing scheme to construct DVR-enhanced flowfields. The algorithm adapts existing multi-time-lag type schemes into one that is well suited for slowly evolving flows with a persistent spatiotemporal structure. Correlation analyses between image pairs across two optimized time scales produce a pair of correlation maps well suited for resolution of targeted high and low measurement velocities. An evaluation map based on the best statistical relative strength of the local correlation peak amplitude and peak ratio is then used to spatially reconstruct a single DVR-enhanced velocity field with a DVR on the order of 1000:1. Numerical simulations show close agreement with measured flows everywhere following DVR enhancement, and the high-DVR PIV results reveal marked differences in the exterior flow kinematics and dynamics due to varying viscous and boundary interaction effects. The inlet velocity profiles at the tube orifice are highly sensitive to the Reynolds number within this range (1-100) and show notable departures from classically assumed uniform pipe entry profiles, impacting flow development lengths downstream. Published under license by AIP Publishing.