Bio-inspired passive ventilation for underground networks.

To decrease the dependence on machinery for ventilation, modern structures seek to incorporate passive ventilation systems [1]. Cynomys ludovicianus (a species of black-tailed prairie dog) have been observed to create underground burrows with asymmetrical openings, one elevated and sharp, the other unelevated and blunt [4]. While research indicates that asymmetric openings serve ventilation purposes, to date, no attempt has been made to model and analyze this system using the laws of fluid mechanics. Analysis of the flow induced inside the burrow owing to this asymmetry suggests that elevating an opening 10 meters while keeping the adjacent opening unelevated creates a pressure difference that can induce a significant mean volumetric flow rate. The shape of openings are modeled as distinct Venturi tubes; analysis reveals the asymmetric shapes leads to a significant increase in the pressure difference of the system, which consequently leads to an increase in mean volumetric flow rate. The values obtained are used to calculate the air changes per hour (ACPH) in a cylindrical underground station, which are determined to be within ASHRAE standards [11]. [ABSTRACT FROM AUTHOR]