Numerical and Experimental Investigation of Airflow inside a Car Cabin

Authors: Mokhtar Djeddou, Amine Mehel, Georges Fokoua, Anne Tanière, Patrick Chevrier

Abstract:

Commuters’ exposure to air pollution, particularly to particle matter inside vehicles, is a significant health issue. Assessing particle concentrations and characterizing their distribution is an important first step in understanding and proposing solutions to improve car cabin air quality. It is known that particle dynamics is intimately driven by particle-turbulence interactions. In order to analyze and model pollutants distribution inside car cabins, it is crucial to examine first the single-phase flow topology and its associated turbulence characteristics. Within this context, Computational Fluid Dynamics (CFD) simulations were conducted to model airflow inside a full-scale car cabin using Reynolds Averaged Navier-Stokes (RANS) approach combined with the first order Realizable k-ε model to close the RANS equations. To assess the numerical model, a campaign of velocity field measurements at different locations in the front and back of the car cabin has been carried out using hot-wire anemometry technique. Comparison between numerical and experimental results shows a good agreement of velocity profiles. Additionally, visualization of streamlines shows the formation of jet flow developing out of the dashboard air vents and the formation of large vortex structures, particularly between the front and back-seat compartments. These vortical structures could play a key role in the accumulation and clustering of particles in a turbulent flow.

Keywords: Car cabin, CFD, hot-wire anemometry, vortical flow.

References:

[1] World Health Organization (WHO), "Health effects of particulate matter. Policy implications for countries in eastern Europe, Caucasus and central Asia," Copenhagen, 2013.
[2] K.-H. Kim, E. Kabir et S. Kabir, «A review on the human health impact of airborne particulate matter,» Environment International, 2015.
[3] L. I. Zaichik, V. M. Alipchenkov and E. G. Sinaiski, Particles in Turbulent Flows, Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA, 2008.
[4] Y. Ishihara, J. Hara, H. Sakamoto, K. Kamemoto and H. Okamoto, "Determination of Flow Velocity Distribution in a Vehicle Interior Using a Visualization and Computation Techniques," SAE Technical Paper, 1991.
[5] A. Piovano, L. Lorefice and O. Scantamburlo, "Modelling of Car Cabin Thermal Behaviour during Cool Down, Using an Advanced CFD/Thermal Approach," SAE Technical Paper, 2016.
[6] P. Danca, F. Bode, I. Nastase and A. Meslem, "On the possibility of CFD modeling of the indoor environment in a vehicle," Energy Procedia, 2016.
[7] T.-B. Chang, J.-J. Sheu, J.-W. Huang and Y.-S. Lin, "Development of a CFD model for simulating vehicle cabin indoor air quality," Transportation Research Part D, 2018.
[8] S. Ullrich, R. Buder, N. Boughanmi, C. Friebe and C. Wagner, "Numerical Study of the Airflow Distribution in a Passenger Car Cabin Validated with PIV," in New Results in Numerical and Experimental Fluid Mechanics XII, 2020.
[9] T.-H. Shih, W. W. Liou, A. Shabbir, Z. Yang and J. Zhu, "A New k-ε Eddy Viscosity Model for High Reynolds Number Turbulent Flows - Model Development and Validation," Computers & Fluids, 1994.
[10] ANSYS Inc, ANSYS Fluent Theory Guide, Canonsburg, 2019.
[11] M. Sosnowski, J. Krzywanski, K. Grabowska and R. and Gnatowska, "Polyhedral meshing in numerical analysis of conjugate heat transfer," in European Physical Journal Web of Conferences, 2018.