Fluctuation Distribution and Vortex Structure of in Three Dimensional Separated Flow

在现有的轴对称体周围分离现象的研究中，似乎很少强调以下几点。一些结果表明，二维型分离出现在三维开放分离开始的位置。首先，油流型分离线与实测压力分布平台边缘偏差较小；其次，迎风侧皮肤摩擦线与主分离线S_1.2不是切交而是正交。在Re=27000,alpha=40‰时，速度的功率谱为19 Hz。该频率可归因于二维模式下的旋涡脱落，如圆柱的理论脱落频率为15hz。扰动的速度和频率在rta =135 at后体处较大，此时正流或反转交替出现。在α <30,Re=8000.4时，侧涡的摆动呈现1 Hz左右的模式，而在α <30,Re=8000.4时则固定在模型表面。在主分离线和次分离线之间的狭窄区域，出现了较强的轴向流反转，与S_1和S_2之间的细长顺时针涡旋模式的上半部分一致。

The followings seem to be rarely emphasized in the existing studies for the separation phenomena around axisymmetric body.1. Some results clarify that the two-dimensional type separation appears away from the start of 3-D open separation. Firstly, the separation lines by oil flow pattern show small deviation from the edges of the plateau of measured pressure distribution. Secondly ,the skin friction lines at windward side intersect not tangentially but normally to the primary separation line S_1.2. The power spectra of the velocity as C.T.A measurement data show the peak frequency of 19 Hz for Re=27000,alpha=40ﾟ. The frequency can be attributable to vortex shedding in two- dimensional mode such as 15 Hz of theoretical shedding frequency for circular cylinder.3. The velocity and frequency of disturbance is large at rheta =135ﾟ at aft body where the positive flow or reversal alternatively appears. The swing of the lateral vortex exhbits the mode of 1 Hz or so at alpha>30ﾟ,while it is fixed on the model surface at alpha<30ﾟ,Re=8000.4. In the narrow region between the primary and secondary separation line the strong axial flow reversal appears,which consist with the upper part of the elongated and clock wise vortical pattern between S_1 and S_2.