The optimal branching asymmetry of a bidirectional distribution tree Original Research Article

Several transportation networks in living systems are pulsatile branching trees. Due to the alternating character of the flow, these trees have to simultaneously satisfy two constraints: they have to deliver the carried products in a limited time and they must exhibit a satisfactory hydrodynamic performance in both directions of the flow. We report here that introducing a systematic branching asymmetry into a distribution tree improves performance and robustness, both at inhalation and exhalation. Moreover, optimizing the asymmetry level for both phases leads to a value very close to the one measured in the human lung.