STUDY ON PREVENTION OF SNOW SMOKE BEHIND TRUCKS IN COLD REGIONS

本研究项目的目的是为了弄清寒冷地区冬季货车后雪烟的产生机理，为预防雪烟的产生提供基本思路。利用风洞进行了实验研究，实验结果如下。风洞中的可视化技术证实了模型车后大尺度涡的演化。大范围的涡流在卡车后面产生雪烟。为了防止大尺度涡的演化，在载货汽车下方安装了尾缘具有三维粗糙度的扰流板。三维扰动对大尺度涡旋的破碎非常有效，扰流板是防止雪烟的有效装置。利用热线风速仪测量了模型车后运动带上的速度场，定量地证实了模型车对湍流强度和大尺度涡的抑制。将上述扰流板安装在实际货车上，并通过行车试验对扰流板的性能进行了校核。结果表明，扰流板对防止泥浆附着在货车尾部表面非常有效，这表明扰流板对货车后部的大范围涡流有抑制作用。发展了三维涡流结构检测技术：通过测量压力脉动，得出了矩形射流中复杂的涡流结构。这项技术有助于了解扰流板后面的涡流运动细节。本工作提出了防止卡车后面的雪烟的基本思路，这些想法还需要进一步的研究来发展。

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.