24 Influence of hydrodynamic parameters on bioaerosol emissions in vortex-driven motion

Abstract Bioaerosol release in vortex-induced systems, which occurs during swirling flows in industrial and domestic settings, is crucial due to its role in airborne microbial dispersion. This phenomenon is governed by heat and mass transfer at the air-liquid interface aerosolisation in a vortex flow. Operational parameters such as rotational speed modulate Reynolds number, turbulence levels, interfacial area, heat transfer and evaporation rate, thereby controlling aerosolisation. Therefore, this study aimed to provide a framework for exploring bioaerosol generation under vortex-induced motion across different parameters. The experiment was performed by using a suspension containing Escherichia coli as an indicator organism, generated by a magnetic stirrer under controlled laboratory conditions. Vortex intensity was controlled across rotational speed, ranging from 500 to 1,200 rpm. Aerosol concentration was monitored using a Condensation Particle Counter (CPC) across multiple ranges (0.2 to 10 µm), with parallel impactor plate sampling (CFU/m³) for microbial viability assessment. Experiments were varied across different speeds to evaluate the combined effects of hydrodynamic and shear stress on particle release. The results revealed that particle count and microbial release increased markedly at high rotational speed, indicating the critical role of reduced surface tension and increased surface turbulence. This research provides a quantitative link between hydrodynamic parameters and the concentration and size distribution of airborne microbial particles. These findings provide potential data to inform engineering control strategies, define thresholds for risk management, and support the development of empirical models for predicting bioaerosol emission rates.