(408b) Slugging Flow of Water Draining From the Bottom of An Unvented Container

Experiments were run to observe the behavior of water draining from the bottom of an unvented container. The container was filled with water and then partially closed with a cap which had a drilled hole. Once the container was turned over and the hole opened, the slugging rate and the drain rate of the water leaving the container were measured. Upon initially opening the hole, the water drains out until the air pressure above the water reduces enough that the air pressure drop from inside to outside of the container supports the water column and the water stops. Air then enters at the bottom through the hole forming a bubble, which grows until reaching a critical size so that it detaches and rises through the water to reach the air space. This added air increases the pressure in the air space enough to allow the water to start flowing again. This cycle of flow out, flow stoppage, and air inflow continues over and over until the hole is closed or the container empties. This is referred to as the ?slugging cycle.?

This paper presents the description of the experiments, data obtained, an analytical model, and comparison of the model to the experimental data. The model predicts a higher flow rate of water out of the container than is observed in the experiment. Therefore, the analytical model predicts a conservatively high flow rate. This model has been applied to the prediction of flow rate out of an opening in the bottom of a large cell containing argon gas and the back flow rate of air into the cell. Some mixing of the gases would occur which would decrease the net flow rates even more. Thus this analytical prediction, which does not allow mixing, is more conservative for the argon-air than the predictions for the water-air experiment.