Frequency and non-linear analysis of bubble paths in bubble chain

In the paper the paths of bubbles emitted from the bras nozzle with inner diameter equal to 1.1 mm have been analyzed. The mean frequency of bubble departure was in the range from 1 to 36 Hz. Bubble paths have been recorded using a high speed camera. The image analysis technique has been used to obtain the bubble paths for different mean frequencies of bubble departures. The Fourier, wavelet analysis and recurrence plots have been used to determine the strength of interac- tion between bubbles in column. It has been found that the influence of previously departing bubbles on trajectory of next bubble in the column can be significant for fb > 30 Hz, in this case the bubble paths become less periodic and more instable. In this case the distance between subsequent departing bubbles (S/D) becomes close to 1. It causes that the vertical interaction between departing bubbles is enough strong to change the dynamical properties of bubble paths.