Bubble plume dispersion from underwater gas leakage: An experimental and dimensionless modelling study

The large-scale bubble plume and intense fountain effect induced by accidental subsea gas releases pose significant safety and environmental risks. This paper aims to experimentally investigate the effects of different leakage conditions on bubble plume dispersion dynamics and quantitatively study the fountain effect, with a focus on the maximum fountain height modelling and prediction. Typical underwater bubble plume dispersion and surface flow evolution were analysed, revealing their related dynamic features. It was found that there was a transition from bubble flow to jet flow with a decrease in nozzle diameter and an increase in leakage pressure in the establishment zone. Both leakage pressure and nozzle diameter could positively strengthen the connection between the frontal bubble cluster and the plume body to prevent rupture. Two surface flow modes dominated by buoyancy force and momentum drive were proposed, and the effects of different leakage conditions on the bubble plume's characteristic parameters, like rising time, steady propagation velocity, maximum plume diameter, open angle and fountain height were discussed. Finally, the correlation between the dimensionless maximum fountain height and $Eu$, $Fr$, $u_s{t}_r/d$ was established by dimensionless and multiple regression analysis. This predictive model exhibits strong generalisation ability that can provide support for potential risk assessment and quantification of underwater gas leakage accidents.