Bubbler design for reservoir destratification

Abstract

Two important bubbler-performance criteria, the mechanical efficiency, η_mech, and the destratification time, Γ, were analysed as functions of two dimensionless parameters, G, the strength of stratification, and M, the source strength. Equations to estimate the optimum airflow rate (via M) and corresponding η_mech and Γ for a known linear stratification G in a reservoir were derived. Owing to difficulties in accurately determining the actual G, it was demonstrated that it is appropriate practice to reduce the design G value by around 10%_. It was shown that the equivalent linear stratification method might lead to sub-optimal design for stratification profiles that deviate substantially from a linear profile. Rather, a bubble-plume model should be applied. Finally, the effects of incorporating changes in bubble radius in a bubble-plume model were examined. η_mech and Γ were found to be relatively insensitive to bubble radius; however, the ideal bubble size for maintaining a suitable oxygen dissolution efficiency is 1 mm.