Flow rectification in loopy network models of bird lungs

TL;DR

This paper demonstrates that multi-loop fluidic networks inspired by bird lungs can rectify oscillatory flows into persistent circulation, with flow control influenced by network topology, oscillation frequency, and amplitude, validated through experiments and simulations.

Contribution

It introduces a novel concept of flow rectification in macroscale networks with loops, inspired by bird lung anatomy, and explores how network topology influences inertial flow control.

Findings

Higher frequencies and amplitudes enhance circulation strength.

Flow separation and vortex shedding enable valving at junctions.

Nonlinear response validated by experiments and simulations.

Abstract

We demonstrate flow rectification, valveless pumping or 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 multi-loop 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.