Keywords: aspiration efficiency, CFD, computational fluid dynamics, particulate matter, GSP samplers, sampling efficiency, flow rate, low flow personal samplers, modelling, air pollution, air quality, commuters, pedestrians, cyclists, cars, buses, Dublin, Ireland
A numerical analysis of the aspiration efficiency of a personal sampler
The impact on sampling efficiency of increasing the flow rate of a low flow personal sampler has been examined. Increases in flow rates were required to obtain sufficient particle mass over the duration of a typical rush hour commute (3.5?16.7 litres/min). Computational Fluid Dynamics (CFD) modelling has been used to assess the implications of this higher flow on the aspiration efficiency of the sampler. The resulting CFD model showed that the high flow sampler has an efficiency marginally less than 100% at wind speeds typically found in transport microenvironments. Practical application of these findings to personal exposure data measured in four modes of transport showed that cyclist and pedestrian concentrations were relatively unchanged when aspiration efficiency is taken into account, due to the wind speeds typically present. However, commuters enclosed in calmer environments, such as the bus and car commuter, were affected by lower aspiration efficiencies.