The numerical simulation of the flow field in the engine compartment of a car is the basis for the evaluation and research of the air flow characteristics in the engine compartment. In this paper, the computational fluid simulation software STAR-CCM+ was applied to simplify the vehicle model of a rear-mounted exhaust. The surface wrapper and surface remesher were used to obtain the whole vehicle surface mesh. Combining with the vehicle wind tunnel model was generated the volume mesh based on Trim mesh sub-regional method. Then, the finite element model of the car engine compartment was established. Three-dimensional flow field in engine compartment was analyzed under reasonable boundary conditions, and found the reflow at climbing is more apparent as compared with that at high constant speed. Then the flow rate experiment of the whole vehicle was obtained wind speed value of the windward surface of the radiator. The error between the simulated value and the experimental value is within 10%, indicating that the simulation model established in this paper is reliable and possesses high simulating accuracy.

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Confined space is a special working place. To ensure the safety, the forced ventilation must be carried out before entering the confined space. In this paper, ventilation process in municipal heating confine space is simulated by CFD numerical simulation method, and the distribution of temperature, oxygen and carbon dioxide in municipal heating confined space during ventilation process is studied. The simulation results show that the airflow and temperature are obviously stratified in vertical direction during the ventilation. The temperature is low and the airflow velocity is high at the bottom part of the tunnel. While the temperature is high and the airflow velocity is low at the top of the tunnel. By contrast, recovery of the oxygen and carbon dioxide content is relatively faster at the bottom than it at the top. When the ventilation volume flow rates are 6000 m 3 •h -1 , 8000 m 3 •h -1 ,10000 m 3 •h -1 , 12000 m 3 •h -1 , and 14000 m 3 •h -1 respectively, the time when the temperature reach stable and gas fraction return to normal are 45 minutes, 32 minutes, 22 minutes, 15 minutes, 10 minutes respectively.

Risk Analysis and Crisis Response under the Background of the Belt and Road (RAC-18