Numerical simulation of particle formation and evolution in a vehicle exhaust plume using the bimodal Taylor expansion method of moments--颗粒学报PARTICUOLOGY

Liu, S., Chan, T. L., & Liu, H. (2019). Numerical simulation of particle formation and evolution in a vehicle exhaust plume using the bimodal Taylor expansion method of moments. Particuology, 43, 46-55. https://doi.org/10.1016/j.partic.2018.02.003

Numerical simulation of particle formation and evolution in a vehicle exhaust plume using the bimodal Taylor expansion method of moments

Shuyuan Liu, Tat Leung Chan ^*, Huijie Liu

Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China

10.1016/j.partic.2018.02.003

Volume 43, April 2019, Pages 46-55

Received 22 June 2017, Revised 22 January 2018, Accepted 21 February 2018, Available online 9 August 2018, Version of Record 19 February 2019.

E-mail: mmtlchan@polyu.edu.hk

Highlights

• A novel bimodal TEMOM coupled with large eddy simulation model was developed.

• The B-TEMOM was verified against MSM and B-QMOM.

• Nanoparticle formation and evolution in turbulent flows were investigated.

• The impact of large coherent structures on the particle dynamics was revealed.

Abstract

The bimodal Taylor expansion method of moments (B-TEMOM) model scheme was developed to simulate the formation and evolution of vehicle exhaust particles. Two independent types of log-normal particle size distributions were selected in the B-TEMOM model scheme, comprising large and small particles to represent background (i.e., the surrounding environment) and vehicle exhaust particles, respectively. Concentration distributions of exhaust and background particles derived using this model scheme were verified against results from a moving sectional method and the bimodal quadrature method of moments, showing excellent agreement. The effects of vehicle tailpipe exit conditions (e.g., exhaust particle concentrations and velocity), sulfur content, and relative humidity on the evolution of particles were investigated numerically. Both two-dimensional and three-dimensional numerical simulations showed that tailpipe exit velocity and relative humidity did not greatly affect the steady-state concentrations or the diameters of particles in urban atmospheres. Although an increase in sulfur content had little effect on the particle concentration, it led to background particles with larger geometric average diameter entering the environment. This coupled CFD-B-TEMOM numerical model provides a simple but accurate and efficient method for studying bimodal aerosol dynamics.

Graphical abstract

Keywords

Vehicle exhaust particles; Bimodal Taylor expansion method of moments; Homogeneous nucleation; Coagulation; Tailpipe exit velocity; Sulfur content and ambient relative humidity

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