New rationale for the effect of multiple buoyancies and their influence on the propagation of respiratory pollutants

Abstract

The effect of buoyancy on fluid flows is a significant consideration in problems relating to energy, the environment, and health. Here, we examine what we term a “multi-buoyancy effect” (MBE), or “fluid-bunching effect,” which is a combination of the Archimedes number (Ar)-related buoyancy resulting from the temperature difference between a fluid flow and the ambient fluid and the Gc number (Gc)-related buoyancy resulting from the temperature difference between the upper and lower boundaries of the fluid domain. A new semi-analytical mathematical model of the jet trajectory is put forward by rational reconstruction. This reveals the physical mechanisms of fluid flows propagating in limited spaces under this MBE. Human respiratory experiments were conducted to show that the MBE can govern the transmission of infective airborne pollutants between people. Our findings provide a new perspective in the transmission of fluid flows and airborne pollutants in limited spaces. They are, thus, also of great interest for predicting the stratification of flows and circulation of the atmosphere and ocean.