Study on Circular Jet Issuing along Cylinder or Pipe Wall

本文研究了沿圆筒外壁和纵向的圆形射流。特别是当壁面射流在远离出口的下游位置分离时，流场的非定常结构受到了关注。为了揭示这一非定常特性，采用了小波分析方法。除了几种常见的小波关联式外，还新引入了小波间歇性，通过这些小波分析方法对分离的流动进行了澄清，得到了以下结论：(1)从平坦度因子和间歇性因子的结果来看，流动的间歇性出现在射流的外缘。这种间歇性似乎对应于分离流，而不是卷起流。(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的结果可以看出，下游位置的流场是非常不稳定的。(3)从两个传感器的小波互相关结果看，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.