The surface airflow characteristics of a van-body truck are investigated by means of force measurement, pressure measurement and flow visualization. The influence of the surface airflow is examined by adjusting the gap and height difference between driv-er cab and van. And the relationship between the flow characteristic and aerodynamic drag are analyzed to provide a reference for designing aerodynamic shape of van-body truck and drag-reducing attachments.

The aerodynamic characteristics of the van-body truck were studied by means of theoretical analysis, numerical simu-lation and wind tunnel experiments. The concept of critical length was presented for the van-body truck in wind tunnel experiments, the proper critical Reynolds number was found and the effects of ground parameters in ground effect simulation on the aerodynamic measure-ments were examined. It shows that two structure parameters, van height and the gap between the cab and the van, can obviously influ-ence the aerodynamic characteristics, and the additional aerodynamic devices, the wind deflector and the vortex regulator in the rear, can considerably reduce the aerodynamic drag of the van-body truck. Numerical simulations provided rich information of the flow fields around the van-body trucks.

In this paper it is proved that the calculation pre-cision of the outside flow field of the van-body truck using RNG k-εturbulence model is higher than that using standard k-εturbu-lence model by means of experiments. The calculation results of the outside flow field of a certain domestic van-body truck are given. And by analyzing and comparing the different tail flow plots, the tail flow structural characteristics and the relationship between the position and the intensity of the tail vortex and the aerodynamic drag is obtained, which can direct the design of the outside aerodynamic shape of the van2body truck.

In this paper, the differences in the characteris-tics of airflow around the van-body truck and of the aerodynamic drag, which were caused by the installation of a wind deflector, were studied by experimentally and numerically. The results show that after the installation of the deflector, the airflow around the top and bottom of the truck becoms smooth, the in-tensity of tail-vortex is weakened and its contribution area less-ened. It also indicates that the aerodynamic characteristics of the airflow are changed distinctly and the aerodynamic drag is re-duced considerably. The effect of the thin-wall deflector is better than the solid one in decreasing the drag. It is also concluded that proper design of the gap between the deflector bottom and the top of the driver cab can enhance the effect of the deflector in reduc-ing drag.

一般CAI课件中习题训练部分明显存在不足。利用计算机模拟人工判题的方法可实现解题过程的智能化。通过利用“字符表”和“图符表”进行人机交互。实现对解题过程中关键步骤、作图方法和所需考核知识点的自动检查、分析和判断。