Intrusion dynamics of particle plumes in stratified water with weak crossflow: Application to deep ocean blowouts

We present an experimental study of particle plumes in ambient stratification and a mild current. In an inverted framework, the results describe the fate of oil droplets released from a deep ocean blowout. A continuous stream of dense glass beads was released from a carriage towed in a salt‐stratified tank. Nondimensional particle slip velocity U N ranged from 0.1 to 1.9, and particles with U N  ≤ 0.5 were observed to enter the intrusion layer. The spatial distributions of beads, collected on a bottom sled towed with the source, present a Gaussian distribution in the transverse direction and a skewed distribution in the along‐current direction. Dimensions of the distributions increase with decreasing U N . The spreading relations can be used as input to far‐field models describing subsequent transport of particles or, in an inverted framework, oil droplets. The average particle settling velocity, U ave , was found to exceed the individual particle slip velocity, U s , which is attributed to the initial plume velocity near the point of release. Additionally, smaller particles exhibit a “group” or “secondary plume” effect as they exit the intrusion as a swarm. The secondary effect becomes more prominent as U N decreases, and might help explain observations from the 2000 Deep Spill field experiment where oil was found to surface more rapidly than predicted based on U s . An analytical model predicting the particle deposition patterns was validated against experimental measurements, and used to estimate near‐field oil transport under the Deepwater Horizon spill conditions, with/without chemical dispersants.