Author ORCID Identifier
0000-0002-1342-6583
Document Type
Dissertation
Date of Award
5-31-2023
Degree Name
Doctor of Philosophy in Mechanical Engineering - (Ph.D.)
Department
Mechanical and Industrial Engineering
First Advisor
Michel Boufadel
Second Advisor
Zhiming Ji
Third Advisor
Pushpendra Singh
Fourth Advisor
Simone Marras
Fifth Advisor
Angelantonio Tafuni
Sixth Advisor
Kenneth Lee
Abstract
Well blowout or oil leakage may occur during the offshore oil exploration activities. A great number of crude oils are released to the water environment in those accidents. Three sequent processes after the blowouts are commonly modelled: the droplet formation near the leakage or orifice, the transport of oil droplets in the water column, and the transport of oil slick with waves near the ocean surface. The oil droplet size distribution (DSD) serves as a vital role as it affects any further process, including chemical process such as biodegradation and physical process such as transport, which provides reference for assessing environmental impact and planning effective responses. The research goal here is focused on the oil droplet size distribution near the releasing orifice.
The present work investigates the oil droplet size distribution in the single-phase jet and multiphase jet using complementary state-of-the-art experimental and computational techniques. The single-phase oil jet was firstly investigated by the vertical jet experiment with two orifices with diameter of 4.7 mm and 10 7 mm in the Ohmsett experiment. Crude oils are released through the pipe with varied flow rate and measurements of oil size distribution were obtained. The DSD results are also used to fit the VDROP-J model (Zhao et al., 2014a), which incorporates jet dynamics and the droplets population balance equation to predict the droplet size distribution. The model is verified, and updated system-dependent parameters are obtained.
The other focus of this study is the prediction of oil droplets under the impact of gas phase and dispersant. When underwater oil blowouts occur, natural gas, such as methane, is released together with oil. Based on the released gas volume, the air-liquid mixture was regarded as bubbly flow in previous studies, where bubbles took a small portion and their influence on the oil droplet sizes was limited. However, the volume of the natural gas released might take a significant portion and form churn flow. In this study, the oil droplet sizes are investigated for the churn flow both experimentally and numerically. The churn flow is found to be closely related to the actual oil blowout scenario where the natural gas enhanced the turbulent mixing and facilitates the breakup of oil droplets, resulting in a smaller oil size distribution. The turbulent energy is investigated using the VDROP-J and it was found out the energy could increase to two times compared to the bubbly flow.
Finally, the oil droplet sizes are investigated under the participation of the dispersant. The dispersant functions as the surfactants used to decrease the interfacial tension between the oil and water. The decreased interfacial tension facilitates the breakup of droplets and therefore reduces the size distribution and accelerates the degradation process. The investigation of dispersant includes the oil sizes after applying dispersant at single jet and multiphase jet.
Recommended Citation
Liu, Ruixue, "Oil droplet size in subsea oil spills: the experimental and numerical investigation" (2023). Dissertations. 1929.
https://digitalcommons.njit.edu/dissertations/1929
