STUDY ON PREVENTION OF SNOW SMOKE BEHIND TRUCKS IN COLD REGIONS

本课题的研究目的是明确寒冷地区冬季卡车后方雪烟的产生机理，获得防止雪烟产生的基本思路。利用风洞进行了实验研究，结果如下：1。利用风洞可视化技术，验证了卡车模型后大尺度涡的演化过程。大尺度的旋涡产生了卡车后面的雪烟。为了防止大尺度涡的演化，在卡车下方附加了尾缘三维粗糙度的扰流片。三维扰动对大尺度涡的破坏是非常有效的，扰流片是防止雪烟的有效装置。用热线风速仪测量了运动带上模型卡车后的速度场，定量证实了模型卡车对湍流强度和大尺度涡的抑制作用。将上述扰流板安装在一辆实际卡车上，并通过驾驶试验对其性能进行了检验。结果表明，扰流板对于防止泥浆附着在卡车后表面是非常有效的，这表明扰流板对卡车后大范围涡的抑制作用。发展了三维旋涡结构的检测技术，通过测量压力波动推导出矩形射流内部复杂的旋涡结构。这项技术对于弄清楚扰流板后面的涡流运动细节非常有用。本文提出了防止卡车后方雪烟的基本思路，还需要进一步的研究来完善。

The object of the research project is to make clear the generating mechanism of snow smoke behind trucks in cold regions in winter season, and to obtain the basic ideas to prevent the generation of snow smoke. The experimental work was carried out by using wind tunnels, and the results are as follows.1. The evolution of large-scale vortices behind a model truck was confirmed by the visualization techniques in wind tunnel. The large-scale vortices generate the snow smoke behind trucks.2. In order to prevent the evolution of large-scale vortices, the spoiler with three-dimensional roughness at the trailing edge was attached under the truck. The three-dimensional perturbation was very effective to break up the large-scale vortices, and the spoiler is a useful device to prevent the snow smoke.3. The velocity fields behind the model truck on the moving belt were measured by hot-wire anemometer, and the suppression of turbulence intensity and large-scale vortices was confirmed quantitatively.4. The above-mentioned spoiler was installed to an actual truck, and the performance of the spoiler was checked by the driving test. The result snows that the spoiler is very effective to prevent the mud adhesion to the rear surface of the truck, suggesting the suppression of the large-scale vortices behind the truck.5. The technique to detect the three-dimensional vortical structures was developed : the complicated vortical structure in a rectangular jet was educed by the measurements of pressure fluctuations. The technique is useful to make clear the details of the vortex motions behind the spoiler.The present work suggested the basic ideas to prevent the snow smoke behind trucks, and the further study is needed to develop the ideas.