Characterizing bubble penetration from a falling stream

The depth that bubbles will penetrate a receiving pool before rising due to buoyancy forces is an important phenomena in designing Low Head Oxygenator (LHO) devices, particularly in an indoor application where the available e levation between the top of the fish tank water column and the inside ceili ng height is limited. The relationship between bubble loss and LHO geometry is unclear. If the submergence of the LHO is less than the bubble penetrat ion depth, excessive escape of bubbles can increase operating costs substan tially. A series of physical experiments were conducted using an elevated b ucket with a single orifice to create a falling stream into a receiving poo l. The primary variables of hydraulic head, hole diameter and fall height w ere varied over a practical range for such applications. Videotaping was us ed to analyze bubble penetration. Regression equations were developed to pr edict both bubble penetration and standard deviation associated with a spec ific set of operating conditions. The standard deviation regression equatio n can be used to predict the statistical Variation in bubble penetration de pth. Bubble penetration depth decreased as fall height was increased and be came stable at a fall height of 50 cm. Bubble penetration increased as hole diameter was increased at all fall heights and hydraulic heads. An example is provided of how to predict bubble penetration depth to meet some user d efined statistical confidence for maximum bubble penetration. (C) 2001 Else vier Science B.V. All rights reserved.