The choice of droplet size probability distribution function for oil spill modeling is not trivial

Abstract

The droplet size distribution (DSD) formed by gas-saturated oil jets is one of the most important characteristics of the flow to understand and model the fate of uncontrolled deep-sea oil spills. The shape of the DSD, generally modeled as a theoretical lognormal, Rosin-Rammler or non-fundamental distribution function, defines the size and the mass volume range of the droplets. Yet, the fundamental DSD shape has received much less attention than the volume median size (d50) and range of the DSD during ten years of research following the Deepwater Horizon (DWH) blowout. To better understand the importance of the distribution function of the droplet size we compare the oil rising time, surface oil mass, and sedimented and beached masses for different DSDs derived from the DWH literature in idealized and applied conditions, while keeping d50 constant. We highlight substantial differences, showing that the probability distribution function of the DSD for far-field modeling is, regardless of the d50, consequential for oil spill response. Highlights► The importance of the oil droplet size distribution function was not known. ► The distribution function of the DSD drives the oil mass distribution patterns. ► First response should consider different d50s and probability distribution functions.

Physical Transport Processes that Affect the Distribution of Oil in the Gulf of Mexico: Observations and Modeling

“…Because a large volume of hydrocarbons may enter such intrusions, far-field models need to track them, along with the droplets and the dissolved oil within and around them (e.g., Vaz et al, 2019). With respect to issues requiring further research, many questions remain about oil droplet size distribution (Faillettaz et al, 2021), as discussed above in the section on Microscale Physical (and Biophysical) Processes. Improvements in the time-varying estimation of initial droplet size distribution as live oil rises from the buoyant plume into the far-field water column will likely result in the next breakthrough.…”

“…Improvements in the time-varying estimation of initial droplet size distribution as live oil rises from the buoyant plume into the far-field water column will likely result in the next breakthrough. These estimates should be based on our understanding of multiphase and pressuredrop processes on the gas portion of the gas-saturated droplets (Griffiths, 2012;Socolosky et al, 2016;Vaz et al, 2020;Malone et al, 2020;Faillettaz et al, 2021), their evolution through partitioning and degassing during oil ascent in the water column (Gros et al, 2016;Jaggi et al, 2017Jaggi et al, , 2020Pesch et al, 2018) and biodegradation (Joye et al, 2016b), and on the acquired knowledge of the effect of subsea dispersant injection (Paris et al, 2012(Paris et al, , 2018French-McCay et al, 2019).…”