Analysis on the dynamic load in a water pool during air discharge from submerged sparger

This paper presents a study of the applicability of the VOF (Volume of Fluid) method to estimation of dynamic load in a water pool induced by oscillation of bubbles that are ejected through sparger holes. We choose the VOF method to simulate this phenomenon, and the pressure of a bubble is given by entropy change in order to consider the compressible effect of the bubble and the effect of gas coming into the bubble. In calculation of air flow rate passing through the holes, the effect of two-phase pressure drop is incorporated. In order to investigate applicability of this method, a simplified blowdown test is carried out. According to the numerical results, the pressure-time history inside the sparger and that in a water pool are both generally reproduced well with analysis except that the magnitude of first peak pressure in a water pool is overestimated. The most likely reason is that the bubble cloud has especially low void fraction at the early stage of bubble formation, and small bubbles around a major bubble work as a buffer, which is discussed in detail in this paper.