Hydrodynamic Optimization of an Ocean-Going Oil Recovery System in Harsh Seas

Abstract

Environmental consequences due to oil spills are disastrous — like the Prestige catastrophe in 2002. Therefore oil combating systems must be developed, which are capable of operating in rough seas. This paper presents the design and optimization of a Seaway independent Oil Skimming system — SOS. The principle of the system is to separate the wave damping from the skimming process without using moving parts. The system consists of a solid pontoon with a bow segment (inverse ramp) and an integrated collection tank (moon pool). The skimmer glides over the oil polluted water surface, smoothing the waves. Subsequently, the oil flows beneath the bow segment to an inlet slit, where a separation blade guides the oil film into the moon pool. Inside the moon pool, a vortex develops behind the bow segment, separating the oil from the main flow and transporting it to the free surface of the moon pool, where it is pumped off. Computational Fluid Dynamics (CFD) calculations and model tests at different scales (1:9, 1:15 and 1:22) with and without oil layer have been conducted. Based on results at different speeds and random seas, the geometry of the separation blade and the moon pool are optimized. Oil tests yield an efficiency of the skimming process up to 90% in random seas and up to 95% in calm water. The assessment of the system includes tests with the skimmer integrated into the carrier vessel MPOSS (Multi Purpose Oil Skimming-System).