Liquid Volume Fluxes in Stratified Multiphase Plumes

This paper presents an optimization scheme to estimate the internal entrained fluid fluxes for multiphase plumes in stratification from indirect experimental measurements and applies the results to field-scale plumes. Experiments were conducted in linear stratification using dispersed phases of air bubbles and glass beads (the latter creating an inverted plume). Comparison of pre- and postexperiment salinity profiles provided direct measurements of the net liquid fluxes in the plume; fluorescence profiles provided direct measurements of the fluxes of passive tracer. To separate the net flux measurements into upward and downward flows this paper applies a constrained Bayesian estimation technique based on a conceptual model of the plume. This method provides estimates of the ambient and counterflowing entrained fluid fluxes, the peeling efficiency (percent of entrained fluid that detrains) and the buoyancy flux continuing above the first peel. These quantities correlate with the nondimensional slip velocity UN, defined as the ratio of the bubble slip velocity us to a characteristic plume fluid rise velocity (BN)1/4; B is the total kinematic buoyancy flux, and N is the buoyancy frequency. The results show that the peeling efficiency is the dominant quantity that controls the plume behavior, and that it is dependent on several processes occurring within the plume. Applications of the results are presented for accidental oil-well blowouts in the deep ocean.