| Automobiles have become an indispensable part of people's daily life.People's requirements for automobiles'performance from the need for basic mobility to the pursuit of higher quality are getting higher and higher.When the automobile is driving at high speed,the interaction of rain and vehicle makes the driver's front windscreen and side window usually have a water obstruction of vision,which is very important for the safety.In severe cases,catastrophic traffic accidents will lead to significant loss of life and property.The problem of the front windscreen visibility can be solved by the vehicle wiper.The contamination on the side window usually comes from the drainage of the wiper and the influence of the rearview mirror.Therefore,it is of great theoretical and practical significance to study the contamination sources and contamination laws of side windows,and to reduce the rain contamination of side windows through effective design.The Lattice Boltzmann method is used for turbulence modeling;DPM model is selected for droplet trajectory tracking and Eulerian wall films model is selected for water film accumulating and moving on body surface.A series of phenomenon that may occur between the droplet and the vehicle surface,such as droplet break-up,splash,and re-entrainment are considered to ensure the accuracy of numerical simulation.The contamination process of the front windscreen and side window is achieved after simulation.The phenomenon of A-pillar overflow is controlled to explore the mechanism of A-pillar overflow.The results show that in addition to the A-pillar overflow contamination,there is still a lot of water contamination caused by the influence of the rearview mirror in the side window.It is mainly due to the unreasonable rearview mirror shape design that disturbs the flow field,which causes the airflow carrying droplets to scour the side window.In order to better analyze and evaluate the impact of rearview mirror on the contamination of side window,the side window is divided into several regions,and the evaluation standard R_C value is established as a quantitative index to measure the severity of contamination.After the contamination mechanism is obtained,ten types of rearview mirror styling factors are established to study the side window contamination,which can change the flow field structure and finally affect the droplet trajectory.Through the simulation,an effective scheme to improve the contamination of side windows is obtained,and several effective factors are combined to obtain an optimized rearview mirror model to explore the correlation and comprehensive effects of various factors.The results show that the R_C value of the side window bottom quadrant is only 0.211,which is41.4%lower than the original model,but lower than the sum of the improvement ratios of all factors,indicating that there is a coupling relationship between the factors.Finally,the optimization model and the original model are evaluated for EWM performance under different speeds and rainfall conditions to verify the applicability of the model.The results show that the optimization model still has good performance at high speed and heavy rain conditions.This paper explores a numerical simulation method based on Lattice Boltzmann method and discrete phase model for studying the contamination of front windscreen and side window of automobiles,analyzes and reveals the influence of different rearview mirror styling factors on side window contamination.And the effects of the size of each factor on the contamination of side windows are explored.The research method and results have important guidance and reference value for the future research and design of rearview mirrors. |
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