Simulation of acoustic backscattering from bubbles and droplets under different shape regimes with implications for underwater detection of leakages using active acoustic sensors.

Safe subsea production of oil and gas, as well as storage of CO2 in geological formations subsea, require rapid detection of accidental releases, eliminating potential harm to the environment. Monitoring of natural gas seeps are important in a climate and environmental aspect.

Previous studies demonstrate the potential of sonars for detection and quantification of oil and gas releases of natural or anthropogenic origin. Simulations of acoustic backscattering from plumes is an important tool for design of leakage detection systems and in situ leakage quantification. Backscattering from subsea leakages are often simulated assuming spherical shapes using, e.g., effective medium theory, however in real world situations bubble and droplets are not spherical. In this study the backscattering from single bubbles (CO2, CH4, and air) and droplets (light and heavy oil) are simulated under different shape regimes (i.e. as a function of Reynolds and Eötvös number). The shapes are extracted from time dependent Computational Fluid Dynamics simulations and the backscattering is modeled using adaptive cross approximation accelerated Boundary Element Method(BEM). The backscattering from single bubbles and droplets are used as input to effective medium theory simulations of plumes. Simulations using BEM and effective medium theory with spherical and non-spherical bubbles and droplets are compared with controlled in situ measurements of backscattering with concurrent shape measurements.

http://dx.doi.org/10.1121/1.4970739