ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-518-9
5th Thermal and Fluids Engineering Conference (TFEC)
STUDY OF THE INTERACTIONS BETWEEN TAILPIPE EXHAUST FLOW AND AHMED BODY WAKE
Resumo
Air quality is a key issue. Cars contribute significantly to the emission of gaseous pollutants. It is crucial to analyse how these pollutants disperse in the wake of a vehicle and infiltrate the car cabin exposing passengers to high concentrations. Here, a 3D numerical study of the flow developing downstream of a simplified car model (squared-back Ahmed body) is presented when a gas (Nitrogen) is emitted from the exhaust pipe. A Reynolds-Average-Navier-Stokes (RANS) model (k-Ω SST) is used coupled with a multicomponent gas method. Parameters for the simulation correspond to experimental investigations led in a wind tunnel to allow comparisons and the validation of the results. Based on the height of the car and the incoming velocity, the Reynolds number is 5×104. Altogether, these conditions correspond to an urban environment. This study focuses on the mixing between air and nitrogen and the flow dynamics in the close wake. We show that the tailpipe flow has no significant influence on the wake flow meaning that it is fully
offset by the momentum of the incoming flow. Comparisons with experimental data obtained in wind tunnel at the same reduced scale are provided. Strong agreements are found for mean and turbulent velocities and for Reynolds stresses validating our model. The results of the volume fraction of nitrogen are also discussed indicating that the gas tracer is captured by the recirculation region due to turbulent structures. These results
could provide interesting indications regarding the positioning of air intake in order to minimize pollutant infiltration.