Intrusion dynamics of small oil droplets released from a deep ocean blowout.

Eric Adams, Dayang Wang, Hayoon Chung

Thursday 2 july 2015

16:00 - 16:20h at Europe 1 (level 0)

Themes: (T) Special session, (ST) Oil spill modelling

Parallel session: 13J. Special session: Oil Spill Modelling

Oil and gas jetted at high velocity, as occurred at the Deepwater Horizon spill, form a buoyant jet that tends to rise toward the surface. However, the smallest droplets separate (detrain) from the plume due to the effects of ambient stratification and current. Such small droplets are expected to be most prevalent when chemical dispersants are applied at the plume source. Our group has previously studied the critical droplet diameter below which detraining droplets enter an intrusion layer and how far they are transported within the intrusion, under linearly stratified but quiescent ambient conditions. Here we extend the study to flowing environments, by towing a source in a flume with dimensions 5m (L) x 1.2 m (W) x 0.6 m (H). Spherical glass beads with SG =2.5 are released as a dense slurry from a carriage at the top of the tank to simulate, in an inverted frame of reference, oil droplets rising from the sea floor. Dyed entrained fluid and particles in the plume and the intrusion layer are observed visually and the pattern of particle deposition (simulating the pattern of droplets rising out of an intrusion layer) is documented by weighing particles collected on a bottom sled towed with the source. The observed pattern of intrusion and deposition are being correlated non-dimensionally with current speed, source buoyancy, stratification and particle/droplet slip velocity, and are also being compared with an analytical model based on potential flow.