Studies on Transportation Mechanics of Sakurajima Volcanic Ash Drifted Over the Fixed Bed Open Channel

樱岛火山灰在固定床明渠上漂流输送力学研究

基本信息

批准号：
01460236
负责人：
KAWAHARADA Reijirou
金额：
$ 3.46万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-01460236/
关键词：
Critical tractive force Ripple Sediment transport Settling velocity 掃流砂滞積砂レン

项目摘要

This experimental investigation have been carried out clarify the transportation mechanics of Sakurajima volcanic ash drifted over the fixed bed open channels, with taking physical properties of ash particles into account. The main findings of the present study can be summarized as follows :1. The ash particles are very angular and jagged, the particle sizes range approximately 0.1 mm to 1.0 mm in diameter in Kagoshima city. The specific gravity of ash range 2.65 to 2.71, these values are a little large than ordinary sand. The settling velocity of ash particles in water are slightly slower than sand.2. The distributions of the velocity over ashed bed channels show the log-law except the near water surface regions. Ordinary ashed bed channels and their turbulence intensities are classified as a smooth channel surface.3. The critical tractive force of ash over the fixed bed is little larger than that of sand, because of the difference of particle feature. Smaller ash particles usually set each other and increase flocculation during dry-process, however the difference between ash and sand tractive force can not be seen in this experiment.4. A free surface flow over the ashed bed generates sediment transportation and ripple form. Ash particles roll and run over the ripple crest and fall at the leeward because of separation, and continues scour and deposition toward the downstream. Ripple length and height do not depend on flow depth, but particle diameter.5. Bed sediment load of ash change according to particle diameter, the smaller, the fewer amount, ash-sediment can not be transported and cleared away in the drainage channel during short period because of changeable hydraulic conditions.

这项实验研究已经进行了，阐明了樱花灰灰的运输力学在固定的床上开放通道上漂移，并考虑了灰分颗粒的物理特性。本研究的主要发现可以总结如下：1。灰分颗粒非常角度且锯齿状，粒度在Kagoshima City的直径约为0.1 mm至1.0 mm。灰分范围2.65至2.71的比重，这些值比普通的沙子大一点。水中的灰分颗粒的沉降速度比沙较慢。2。灰烬床通道上速度的分布显示了除近水面区域外的日志定律。普通的灰烬床通道及其湍流强度分类为光滑的通道表面3。由于粒子特征的差异，固定床上灰分的临界拖动力比沙子的临界力大一点。较小的灰分颗粒通常相互设置并增加干燥过程中的絮凝，但是在本实验中无法看到灰分和砂拖运力之间的差异4。灰烬床上的自由表面流动产生沉积物的运输和涟漪形式。灰分颗粒滚动并在波纹冠上滚动，由于分离而落在背风，并继续沿着搜索和沉积向下游。纹波长度和高度不取决于流量深度，而是颗粒直径5。根据颗粒直径，由于可变的液压条件，在短时间内无法在排水通道中运输并清除灰分的灰分负荷，较小，较小，灰分量越少。