BARRIER FAILURE BY CRITICAL ACCUMULATION OF VISCOUS OIL

ABSTRACT A barrier may fail to contain an oil slick because of drainage failure, droplet entrainment failure, or critical accumulation. Drainage and entrainment failure are well known. The present paper introduces the phenomenon of critical accumulation, that is, the unstable reduction of the slick to an infinitely small length when a layer of highly viscous oil is exposed to a relative oil-water flow velocity exceeding a certain critical velocity Uca. The reduction to an infinitely small slick length causes all the oil to pass underneath the barrier independent of the barrier draft. Experiments on barrier failure were performed in two laboratory flumes using a wide range of oil types and oil viscosities. Critical accumulation always occurred with oil viscosities v0 ≤ 3,000 cs. The critical relative velocity was Uca ≃ 0.15 m/s for oil with 3,000 cs < v0 < 20,000 cs, with a slight increase in Uca for higher viscosities. Uca is independent of other oil and hydrodynamic parameters. The findings of the study ...