Study on Circular Jet Issuing along Cylinder or Pipe Wall

本文研究了沿圆柱体纵向和沿着外壁喷射的圆形射流。特别地，注意力集中在流场的非定常结构，其中壁射流在远离出口的下游位置分离。为了揭示这种非稳态特性，采用了小波分析。除了一些常用的小波相关性外，本文还引入了小波不相关性。通过这些小波分析方法，对分离流进行了澄清，得到了如下结论。(1)由平面因子和不均匀性因子的计算结果可知，射流的不均匀性出现在射流的外缘。这种不稳定性似乎与卷起流之外的分离流相对应。(2)为了揭示流动的不稳定性，引入了小波分析。从小波变换和小波自相关分析的结果可以看出，下游区域的流场是相当不稳定的。(3)从使用两个传感器的子波互相关的结果中，可以看出大尺度结构通过并长大。

The circular jet which issues along the outer wall and in the longitudinal direction of the cylinder has been investigated in this paper. Especially, attention is focussed on the unsteady structure of the flow field where the wall jet separates at the down stream location far form the exit. In order to reveal this unsteady property the wavelet analysis was used. In addition to some ordinary wavelet correlations, the wavelet intermittency was newly introduced Though these wavelet analytic methods the separated flow has been clarified The obtained conclusions as follows.(1) From the results of flatness factor and intermittency factor, the intermittency of the flow appears in outer edge of the jet. This intermittency seems to correspond to the separating flow besides the rolling up flow.(2) In order to reveal the unsteadiness of flow, some wavelet analysis were introduced. From the results of the wavelet transfrom and wavelet auto-correlation, it has been clarified the flow field in the downstream location is unsteady considerably.(3) From the results of wavelet cross-correlation by using two sensors, the large scale structure is seen to pass and grow up.