CFD Modeling of Particulate Matter PM2.5 inside BRT public transport buses

Abstract

High pollution levels have been detected by local air quality monitoring network in Bogotá. Vehicle emissions are an important and direct source of pollution, heavy traffic roads are places where particulate matter pollution presents high concentrations and population exposure. Assessment of the exposure levels of passengers inside the massive transport system is an important case of study in megacities such as Bogotá due to the long residence time of the passengers. Bus Rapid Transit BRT has been implemented at the beginnings of the years 2000’s in the city of Bogotá. This is one of the most representative cases worldwide and it has spread the model around cities like Cali, Bucaramanga and Cartagena. The aim of this study is to perform a CFD modeling evaluation to provide detailed information regarding the passenger exposure in massive public transport system. CFD modeling of particulate matter dispersion inside bus can help identifying “hot-spots” of pollution. The developed modeling considers the conditions of the bus when there is low passenger traffic, windows open and cruise speed of 60 km/h. Data-set obtained for particulate matter was measured in real time and used for model validation, pre-processing and post-processing stages. A BRT transport system is characterized by the existence of an exclusive lane for the articulated buses, which operate normally using diesel fuel. This public transport model results attractive for third world countries thanks to its low costs in respect of subway systems. Pollution levels in the cities where it is implemented the BRT model usually present unfavorable Air Quality Indexes, which implies that the users of the system are exposed to contaminants presents in the air, like particulate matter PM2.5, associated directly with diesel burn and with cardiovascular illnesses and lung cancer. With the aim of knowing the PM2.5 levels inside of public transport buses, in a spatially and temporally detailed form, a CFD model was implemented and validated with data obtained from a measuring campaign. This allows analyzing the pollution levels at which are exposed every day the passengers of the public transport system BRT in the city of Bogotá