41 Optimal Tomography--レーザー密度計

Abstract

Generally, the density change ofaliquid is measured using the change of elecldcal conductivity. The conventionaldensity meter has the deficits that the probe itself disturbs the flow field and it can measure only the density change at the point.The my path ofalaser beam is deflected when it is shed into a strntifeid fluid due to the change of the deflectionratio of ligllt by the density difference of liquid. In many cases, this is unfavorable property for the flow measurement. This reserach aims at the development ofanew type density meter using this property.Afunctional form such as the polynominals, the Fourier series and other orthogonal functions which contain a fewarbitrary parameters is assumed to express the density filed. The path of laser beams are calculated by solving thedifferential equiation ofray deflection. The true values of parameters are invecsly estimated by the Marquazdt methodso as to minimize the squared errors between the calculated and measured points oflaser ray emmision.The position of lase ray emmision is measured precisely and quickly by PSD (Position Sensing Dcvice). The direction oflaser beam is changed by the combination of a rotating mirror and reflection minors, in order to increasethe amount of information, i.e. the number oflaser rays.The density chnges ofstratifeid flow are correctly estimated for (a) one dimensional vertical density filed, (b) the internal waves of two-layerd flow and (c) complicated density field around an isolated mountain ridge.