だ円断面管路内助走区間発達乱流構造の実験解析

抄録

An experimental study of the developing turbulent flow in an elliptical duct with an aspect ratio of 2 : 1 was carried out using a laser-Doppler anemometer. It is pointed out from numerical analysis that the intensity of the secondary flow of the second kind shows a maximum value before the flow becomes a fully developed turbulent flow. Therefore, special attention was paid to the measurement of Reynolds stress and the secondary flow of the second kind in developing turbulent flow in order to confirm the numerical prediction. Since it is very difficult to measure the secondary flow of the second kind because of its low intensity, we utilized a laser-Doppler anemometer which can measure flow without disturbing the flow field As a result of this study on developing turbulent flow, the experimental distribution of the secondary flow is found to coincide with the numerical prediction ; therefore, the features of developing turbulent flow include the highest intensity of the secondary flow. At the same time, a clear distinction of the distribution of five of the six Reynolds stresses was made, showing their characteristic aspects. The experimental results, except for the normal stress in the vertical direction, agree with numerical predictions without much discrepancy.