STUDY OF 3-DIMENSIONAL INTERTACTINS BETWEEN WAKE VORTICES AND FLOWS NEAR SEPARATION LINES

本文采用粒子图像测速、数值模拟等三种方法研究了α=30 °、40 °和50 °入射角下轴对称抛物面的三维分离流场。粒子图像测速：提供示踪剂，配雾机或塑料气球。本文用激光片光研究了流动截面上的旋涡结构，并采用了双色激光双扫。利用二向色镜将氩激光束分离为蓝、绿色光，实现了PIV技术的应用。在α=30或40 °时的速度测量结果显示与以下风速计结果的偏差最多为20%，其中雷诺数为9000（参考底部直径）。数值模拟：采用拟压缩性方法和Beam and Warming方法对流动进行数值模拟。结果进行了比较与 关于我们 风速测量实验并认识到，预测是好的40度和50度的情况下，出现强涡。热线风速仪。在与PIV研究相同的条件下，用热线风速仪对流动进行了实验研究。雷诺数分别为9.0×10^3和1.8×10^4（以底部直径为基准）。用X型探头测量了三维速度场。在采样时间为4kHz的速度波动也进行了评估。输出信号显示了不同截面上均方根值和雷诺应力的变化，均方根值大的位置空间相关因子较小。本文用激光片光法研究了分离流中的旋涡结构。在每个横截面的身体的横向涡的发展是可视化的。图中显示了每个横截面、攻角和雷诺数下涡型的变化。通过风速测量和可视化的结果，证实了在大α（如50 °）时，背风涡与物体后尾流中的速度脉动不稳定地相互作用。少

Three dimensional separated flow over axisymmetric paraboloid at incidence angles ; α=30, 40 and 50 deg has been investigated by three approaches such as particle image velocimetry, numerical study. and measurement with constant temperature anemometer.Partcle image velocimetry : Supplying tracers with a fog machine or plastic balloons. Laser light sheet is used in studying the structure of the vortices in cross-sections of flow, for which two-color Laser dual sweep has been employed. The user-friendly PIV technique has been developed with separating Argon laser beam into Blue and Green by dichroic mirror, and the flow reversal can be detected. Velocimetry results at α=30, or 40 deg shows at most 20% deviation from the following anemometer results, where Reynolds numbers is 9000 referred to the base diameter.Numerical simulation : The attempt of numerical simulation of the flow is performed with a pseudo-compressibility method with Beam and Warming method . The results are compared with … More the anemometry experiment. and it was realized that the prediction is good for the 40deg and 50 deg cases where strong vortices appear.Hot wire anemometry. The flow at the same condition as in PIV study has been investigated experimentally with a hot wire anemometer. Reynolds numbers are 9.0×10^3 and 1.8×10^4 referred to the base diameter. X-type probe has been used to measure three dimensional velocity fields. Velocity fluctuations at sampling time of 4kHz have been also evaluated. The output signals show the change of R.M.S.value and Reynolds stress in various cross-sections and that the spatial correlation factors are small at the locations of large R.M.S.value. Laser light sheet method is used in studying the structure of the vortices in separated flow. The development of lateral vortices in each cross-section of the body is visualized. The variation of vortex patterns is shown for each cross-section, angle of attack and Reynolds number. With both results of anemometry and visualization, it has been confirmed that at large αsuch as 50 deg, the leeside vortex interacts unsteadily with the velocity fluctuations in the wake behind the body. Less