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Development of the instantaneous measurement system of 3-dimensional sediment concentration distribution by LASER sheet emission

激光片发射三维泥沙浓度分布瞬时测量系统研制

基本信息

批准号：
06555151
负责人：
HINO Mikio
金额：
$ 5.89万
依托单位：
Chuo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

Need for the instantaneous measurement of 2-or3-dimensional sediment concentration distribution are high in order to understand the mechanism of sediment transportation and bed configuration changes in rivers. However, at present time, the only means of sediment concentration detection is a device applying photo-electronic cell.We intended to develop an instrument for instantaneous measurement of 2-or 3-D sediment concentration by applyng the CT (computer tomography) technique. Especially, the following items are aimed at ;(1) The instrument must not distrib flow fields.(2) The measurement is made instantaneously.(3) The instrument should be compact and portable for use in laboratories as well as fields.(4) The price of the instrument is as low as possible for use by common researchers.A row of laser emitters is placed on a line parallel to the mean flow. Extenciton rate of laser intensity is measured and recorded by ray receivers positioned on an opposite site. The concentration field is expressed either by the double Fouries series (complex variable) or by the virtual plate and load method (which has been proposed by the head investigator, M.Hino, in 1975). The problem reduces to a kind of computer tomography of solving a system of linear simulaneous equations.This instrument was constituted of a scanning multipoint laser light transmitting unit, a photo detection array and a data processing unit whose software is operated based on the principle of the inverse estimation. Some laboratory test for a real concentration field proved the usefulness of the instrument. The method of virtual load proved to be superior to the double Fourier series expansion. By the former method, a more complicated concentration field can be expressed by a lesser number of expansion coefficients, the errors included in measured LASER intensity are easily cancelled.

为了了解河流泥沙输移和河床形态变化的机理，迫切需要对二维或三维含沙量分布进行瞬时测量。然而，目前测量含沙量的唯一手段是采用光电池式的装置，我们打算利用CT(计算机层析成像)技术来研制一种二维或三维含沙量的瞬时测量仪。特别针对以下几个方面：(1)仪器不能散布流场。(2)测量是瞬时进行的。(3)仪器应紧凑，便于在实验室和野外使用。(4)仪器的价格尽可能低，便于普通研究人员使用。一排激光发射器被放置在与平均流量平行的直线上。激光强度的激发速率由位于相对位置的射线接收器测量和记录。浓度场可以用双傅立叶级数(复变量)表示，也可以用虚拟平板加载荷法(1975年由首席研究员M.Hino提出)表示。该仪器由扫描多点激光发射单元、光电探测阵列和数据处理单元组成，其软件运行基于逆估计原理。通过对实际浓度场的实验室测试，证明了该仪器的实用性。结果表明，虚载荷法优于双傅立叶级数展开法。用前一种方法可以用较少的展开系数表示较复杂的浓度场，容易消除测量激光强度的误差。