On the wavelet analysis of the oscillatory phenomena in He II film boiling

摘要

Continuous wavelet transform (CWT) is employed in the analysis of the pressure oscillation and the temperature oscillation in the film boiling of He II. The CWT analysis results provide the detailed time-varying frequency content, which can not be obtained in the ordinary Fourier transform. It can display the information about transient oscillatory behavior in both time and frequency domains, while Fourier transform only yields the time-averaged frequency content of the whole transient process. It could be understood from the CWT analysis results of the pressure oscillation and the temperature oscillation that the dominant frequency of the bubble oscillation is characterized by the highlighted patterns throughout the time domain. The dominant frequency varies locally in the time domain, which is directly connected with the vapor bubble behavior in the transient film boiling process.