Flow Rectification in Loopy Network Models of Bird Lungs

We demonstrate flow rectification, valveless pumping, or alternating to direct current (AC-to-DC) conversion in macroscale fluidic networks with loops. Inspired by the unique anatomy of bird lungs and the phenomenon of directed airflow throughout the respiration cycle, we hypothesize, test, and validate that multiloop networks exhibit persistent circulation or DC flows when subject to oscillatory or AC forcing at high Reynolds numbers. Experiments reveal that disproportionately stronger circulation is generated for higher frequencies and amplitudes of the imposed oscillations, and this nonlinear response is corroborated by numerical simulations. Visualizations show that flow separation and vortex shedding at network junctions serve the valving function of directing current with appropriate timing in the oscillation cycle. These findings suggest strategies for controlling inertial flows through network topology and junction connectivity.

Automated summary

This study demonstrates flow rectification, valveless pumping, or AC-to-DC conversion in macroscale fluidic networks inspired by the unique anatomy of bird lungs. Experiments show that higher frequencies and amplitudes of imposed oscillations generate disproportionately stronger circulation, which can be controlled through network topology and junction connectivity. Visualizations reveal that flow separation and vortex shedding serve as the valving function of directing current with appropriate timing in the oscillation cycle.