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STUDY OF THE INTERACTIONS BETWEEN TAILPIPE EXHAUST FLOW AND AHMED BODY WAKE

C. Blanchard
University of Windsor, Ontario, N9G 3P4, Canada; ESTACA West Campus, Laval, 53000, France

Ram Balachandar
University of Saskatchewan, Collage of Engineering, 57 Campus Drive, Saskatoon, S7N 5A9; Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, Ontario, N9B3P4, Canada; Department of Civil and Environmental Engineering, University of Windsor, Windsor, Ontario, N9B 3P4, Canada

Frederic Murzyn
ESTACA West Campus, Laval, 53000, France

DOI: 10.1615/TFEC2020.tfl.031916
pages 681-685

Abstract

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.

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