Bacterial aerosol neutralization by aerodynamic shocks using a novel impactor system: Design and computation

摘要

Neutralization of bacterial aerosol releases is critical in countering bioterrorism. As a possible bacterial aerosol neutralization method that avoids the use of chemicals, we investigate the mechanical instabilities of the bacterial cell envelope in air as the bacteria pass through aerodynamic shocks. To carry out this fundamental investigation, a novel experimental impactor system is designed and built to simultaneously create a controlled and measured shock and to collect the bacteria after they pass through the shock. In the impactor system the aerosol flows through a converging nozzle, perpendicular to a collection surface that has an orifice through which the shocked bacteria enter the deceleration tube. Both experimental measurements of the pressure in the impactor system at multiple points and computational fluid dynamics simulations are used to quantitatively characterize the shocks created in the impactor. Specifically, the developed computational model describes the evolution of both the gas and the particle velocity and temperature in the impactor system to determine the forces exerted on the bacterial aerosol as they pass through the shock. The results indicate that the developed computational model predictions compare well with the experimental pressure measurements. The computational model is also used to predict the magnitude of the acceleration needed to neutralize various bacterial aerosols and guide on-going experimental work.