Physics of Microbial Bioaerosols
Bioaerosol droplets may be generated from a suspension of microorganisms sprayed into the atmosphere as a polydipersed aerosol, that is, a dispersion made up of many different sized droplets. There, each droplet follows its unique trajectory all the while evaporating to a packed residue of particles. The shape and size of the residue particle depends on the quality and quantity of microorganisms in the droplet. The rate of evaporation (or condensation) of solvent in the droplet, usually water, depends on chemical parameters that control droplet evaporation (condensation) such as the droplet solvent and solute, and ambient relative humidity (RH) and temperature. Physical forces which are acting on a droplet/particle in motion are atmospheric drag which usually tends to slow a particle from the bulk air velocity and changes with droplet size and shape, and gravity, which usually accelerates a particle to its terminal settling velocity. On a larger scale, droplets are dispersed by the atmospheric motion and carried downwind where they are impacted or settle onto surfaces. Electrostatic forces may be important in attracting particles to surfaces, including the surface of other particles or droplets.
KeywordsReynolds Number Droplet Size Terminal Velocity Spray Nozzle Droplet Evaporation
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