Development of Fluidics-Type Sprinkler to Remove the Fallen Volcanic Ash from Mt.Sakurajima

作为对落在太阳集热器上的火山灰清除装置研究的一部分，设计并研制了一种应用流控装置流动机理的新型喷头。本研究利用摄像机和图像处理系统，研究了洒水的扩散角。此外，还对喷淋水的分布进行了定量测量。在本次研究中，对研制的喷头设置的气孔直径进行了不同程度的改变。本研究得到的结论如下：(1)随着气孔直径变大，洒水的扩散角变宽。在一定直径下，扩散角达到最大值，然后逐渐减小。(2)喷淋水的分布随气孔直径的变化较大。在直径较小的情况下，水主要分布在水射流中心线周围，其分布呈尖边锥状。然而，随着直径的增大，水滴的分布呈鞍形分布。喷淋水的最大深度出现在射流的外缘。(3)为了定量估计喷淋水的分布，新引入了喷淋水平均深度。因此，当水呈锥状分布时，平均深度较大。然而，根据洒水分布的均匀性，它变小了。

As a part of the investigation on the device to remove the volcanic ash fallen on the sun-heat collector, new type of sprinklers applied the flow mechanism in the fluidic devices have been designed and developed. In this study, by using the video camera and the image processing system, the spread angle of the sprinkled water have been investigated. Moreover, the distribution of the sprinkled water have been measured quantitatively. Inthis investigation, the diameter of the air hole set in the developed sprinkler were changed variously. The obtained concludions in this study are as follows.(1) As the diameter of the air holes becomes large, the spread angle of the sprinkled water widens. However, at a certain diameter the spread angle has a maximum value, and then it lessens gradually.(2) The distributions of the sprinkled water change greatly with the diameter of the air hole. In the case of small diameter, water is distributed around the water jet center-line mainly and its distribution is shaped like a sharp edge cone. However, as the diameter increases the distribution of the sprinkled water changes into the saddle-shape one. The maximum depth of the sprinkled water shows at the outer edge of the water jet.(3) In order to estimate the distirbution of the sprinkled water quantitatively, the mean depth of the sprinkled water was introduced newly. As a result, the mean depth is large in the case that water distributes in the shape of cone. However, it becomes small according to the uniformity of the sprinkled water distribution.