STUDY ON PREVENTION OF SNOW SMOKE BEHIND TRUCKS IN COLD REGIONS

本课题的研究目的是弄清寒冷地区冬季货车后雪烟的产生机理，并获得防止雪烟产生的基本思路。利用风洞进行了实验研究，得到了如下结果.通过风洞显示技术，证实了模型车后大尺度涡系的演化过程。大尺度的涡旋产生了卡车后面的雪烟。为了防止大尺度涡的发展，在尾缘加装了三维粗糙度扰流片。三维扰动对大尺度涡系的破碎非常有效，扰流片是一种有效的防雪烟装置.采用热线风速仪测量了模型车后的速度场，定量地证实了该方法对湍流强度和大尺度涡的抑制作用.将上述扰流器安装到实车上，并通过行驶试验对扰流器的性能进行了检验。研究结果表明，扰流器对防止泥浆附着在卡车后表面是非常有效的，这表明扰流器抑制了卡车后的大尺度涡流.发展了三维涡结构的检测技术：通过压力脉动的测量导出了矩形射流中复杂的涡结构。该技术有助于了解扰流器后涡运动的细节，为防止车后雪烟的产生提供了基本思路，还需进一步研究。

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.