Abstract:

：In order to investigate the complexity characteristics in the jet mixing zones of the circulating jet tank (CJT), a dynamic data acquisition system is employed to measure the instantaneous Pressure fluctuation signals (PFS) at different axial, radial and circumferential positions. The optimal data lengthi=110 000 is extracted based on the distributions of standard deviation (σ), the kurtosis (K), and the skewness (S) of the PFS. Based on the finite statistical complexity, the comparison among the synthetic method, dynamic method, and static method shows that the synthetic method behaves the highest adaptability. The most optimal wavelet decomposed scale is obtained. The complexity of PFS in the CJT is analyzed at different scales based on the finite statistical complexity and complexity. The results show that distribution trends of two kinds of complexity of PFS in the CJT are similar. Based on the multi-scale analysis of PFS, the values of complexity measure sharply decay then slightly decrease with the increasing decomposed scales, which indicate that the flow stability become stronger. The complexity measure of approximation PFS at scale J=10 with the frequency band of 0~0.98 Hz approaches to zero, which shows that the flow in the CJT appears periodic flow. There are multi scale flow structures which compose global stabilization and local instability in the CJT.

Key words: finite statistical complexity, multi-scale, pressure fluctuation, circulating jet tank