Experimental investigations into the pulsations of void fraction averaged in a short axial distance and static pressure were carried out in a vertical upward air-water two-phase flow. The flow patterns concerned were mainly slug and froth flows. The relationship between pulsations of these quantities was examined based on the statistical properties such as the intensity, the histogram and the spectrum density distribution. The simulation of pressure pulsation was also examined.
The main results obtained are summarized as follows:
(1) The void distribution along the tube changes as the bubbles rise. The larger the gas flow rate, the larger the rate of change.
(2) Flow pattern is characterized by the shape of the histogram of the void fraction. However, there is no fundamental difference between the shapes in slug and froth flows.
(3) The peak frequency in the spectrum density distribution of pressure pulsation does not always agree with that of void fraction. The latter tends to be larger than the former.
(4) The simulation of pressure pulsation proposed in this paper is varied in typical slug and froth flows. In the transition region from slug to annular flow, however, the time varying pressure pulsation cannot be calculated accurately if a rule observed in the series of gas slug length is neglected.
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