Progress in operational modeling in support of oil spill response

Following the 2010 Deepwater Horizon accident of a massive blow-out in the Gulf of Mexico, scientists from government, industry, and academia collaborated to advance oil spill modeling and share best practices in model algorithms, parameterizations, and application protocols. This synergy was greatly enhanced by research funded under the Gulf of Mexico Research Initiative (GoMRI), a 10-year enterprise that allowed unprecedented collection of observations and data products, novel experiments, and international collaborations that focused on the Gulf of Mexico, but resulted in the generation of scientific findings and tools of broader value. Operational oil spill modeling greatly benefited from research during the GoMRI decade. This paper provides a comprehensive synthesis of the related scientific advances, remaining challenges, and future outlook. Two main modeling components are discussed: Ocean circulation and oil spill models, to provide details on all attributes that contribute to the success and limitations of the integrated oil spill forecasts. These forecasts are discussed in tandem with uncertainty factors and methods to mitigate them. The paper focuses on operational aspects of oil spill modeling and forecasting, including examples of international operational center practices, observational needs, communication protocols, and promising new methodologies

Development of the CSOMIO Coupled Ocean-Oil-Sediment- Biology Model

The fate and dispersal of oil in the ocean is dependent upon ocean dynamics, as well as transformations resulting from the interaction with the microbial community and suspended particles. These interaction processes are parameterized in many models limiting their ability to accurately simulate the fate and dispersal of oil for subsurface oil spill events. This paper presents a coupled ocean-oil-biology-sediment modeling system developed by the Consortium for Simulation of Oil-Microbial Interactions in the Ocean (CSOMIO) project. A key objective of the CSOMIO project was to develop and evaluate a modeling framework for simulating oil in the marine environment, including its interaction with microbial food webs and sediments. The modeling system developed is based on the Coupled Ocean-Atmosphere-Wave-Sediment Transport model (COAWST). Central to CSOMIO’s coupled modeling system is an oil plume model coupled to the hydrodynamic model (Regional Ocean Modeling System, ROMS). The oil plume model is based on a Lagrangian approach that describes the oil plume dynamics including advection and diffusion of individual Lagrangian elements, each representing a cluster of oil droplets. The chemical composition of oil is described in terms of three classes of compounds: saturates, aromatics, and heavy oil (resins and asphaltenes). The oil plume model simulates the rise of oil droplets based on ambient ocean flow and density fields, as well as the density and size of the oil droplets. The oil model also includes surface evaporation and surface wind drift. A novel component of the CSOMIO model is two-way Lagrangian-Eulerian mapping of the oil characteristics. This mapping is necessary for implementing interactions between the ocean-oil module and the Eulerian sediment and biogeochemical modules. The sediment module is a modification of the Community Sediment Transport Modeling System. The module simulates formation of oil-particle aggregates in the water column. The biogeochemical module simulates microbial communities adapted to the local environment and to elevated concentrations of oil components in the water column. The sediment and biogeochemical modules both reduce water column oil components. This paper provides an overview of the CSOMIO coupled modeling system components and demonstrates the capabilities of the modeling system in the test experiments

Evaporating pure, binary and ternary droplets: thermal effects and axial symmetry breaking

The Greek aperitif Ouzo is not only famous for its specific anise-flavored taste, but also for its ability to turn from a transparent miscible liquid to a milky-white colored emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions [H. Tan et al., Proc. Natl. Acad. Sci. USA 113(31) (2016) 8642]. Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni flow. By using image analysis techniques and micro-PIV measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence

Material Transport in the Ocean Mixed Layer: Recent Developments Enabled by Large Eddy Simulations

Material transport in the ocean mixed layer (OML) is an important component of natural processes such as gas and nutrient exchanges. It is also important in the context of pollution (oil droplets, microplastics, etc.). Observational studies of small-scale three-dimensional turbulence in the OML are difficult, especially if one aims at a systematic coverage of relevant parameters and their effects, under controlled conditions. Numerical studies are also challenging due to the large-scale separation between the physical processes dominating transport in the horizontal and vertical directions. Despite this difficulty, the application of large eddy simulation (LES) to study OML turbulence and, more specifically, its effects on material transport has resulted in major advances in the field in recent years. In this paper we review the use of LES to study material transport within the OML and then summarize and synthesize the advances it has enabled in the past decade or so. In the first part we describe the LES technique and the most common approaches when applying it in OML material transport investigations. In the second part we review recent results on material transport obtained using LES and comment on implications

Numerical simulation of droplet dispersion and deposition in pipes

Multiphase flows are commonly encountered in industrial processes but remain challenging to predict. The role of droplets in the setting of various flow patterns seen in pipes is capital. Being able to simulate accurately the motion, the dispersion, the deposition and the entrainment of droplets from a liquid film or pool would allow refining the various numerical models and would provide a useful insight to people involved with such flows. The PhD work summarised in this thesis aims at answering that ambitious goal, i.e. to reproduce the whole "life" of a cloud of droplets, with application to pipes and industrial systems. To the author’s knowledge, such study has never been realized with any open source computational fluid dynamics code such as OpenFOAM and in such details. An original surface-tracking motion has also been developed to solve wavy-stratified flows and droplets entrainment by extending OpenFOAM’s capabilities. The Lagrangian framework has been selected for this study as the relationship with various forces could be expressed directly and statistical information, including any Eulerian field if needed, could be retrieved

Vibration-induced mobilization of trapped non-aqueous phase liquids in porous media

Acoustic wave stimulation, such as vibration-induced mobilization, is a promising enhancement approach to remove trapped NAPLs (Non-Aqueous Phase Liquids) usually encountered in multiphase flows through porous media, especially the remediation of underground water contamination and incomplete petroleum recovery from oil reservoirs, with advantages of high efficiency, low cost and environmental safety relative to traditional mobilization methods;According to a simple hypothesized capillary-physics mechanism, specific predictions can be deduced that vibration will be the most effective in mobilizing trapped non-aqueous phase liquids with a comparative higher acceleration amplitude and lower vibration frequency;Quasi-two-dimensional glass micro-model experiments were carried out and it was shown that for fixed acceleration amplitude TCE (trichloroethylene), the trapped organic phase, was more quickly displaced as the vibration frequency decreased from 60 Hz to 10 Hz. And for fixed vibration frequency, TCE displacement became more and more efficient as the acceleration amplitude increased from 0.5 m/s2 to 5.0 m/s2;Moreover, numerical simulations were performed using FLUENT to investigate single droplet flow and the related stimulation effects of vibration. Implementing vibration was demonstrated to be more helpful and efficient to mobilize a trapped droplet in capillary tubes. For fixed acceleration amplitude, the efficiency increases as the vibration frequency decreases from 50 Hz to 10 Hz. For fixed vibration frequency, the average bulk flow rate increase and the time necessary to mobilize the trapped droplet decrease as the acceleration amplitude increase;In addition, analysis of droplet breakup in constricted capillary tubes driven by interfacial tension was performed. A criterion was derived to determine whether droplet breakup could be initiated in sinusoidally constricted tubes, and was further validated by simulations and published data. Droplet breakup was shown to be strongly dependent on the shape of the constriction, viscosity ratio, and interfacial tension, but not on density ratio;In all, the work together with the capillary physics mechanism can make it possible to understand the physics of the mobilization effect of low frequency vibration, which can then be applied to the predictions of the stimulation effect in the field after further full parameter space investigations are performed

Assessment of LES-STRIP approach for modeling of droplet dispersion in diesel-like sprays

International audienceIn this paper, the stochastic equations of droplet motion in turbulent flow, proposed recently by Gorokhovski and Zamansky (2018, Phys. Rev. Fluids 3, 3, 034602), are assessed for turbulent spray dispersion in diesel like conditions along with Large Eddy Simulation (LES) for the gaseous flow. For droplets above the Kolmogorov length scale, this model introduces the concept of the stochastic drag, independently of laminar viscosity. For droplets below the Kolmogorov length scale, the model equation does depend on the laminar viscosity through the Stokes drag but the particle motion is stochastically forced. Both the stochastic drag and the stochastic forcing of the Stokes drag equation are based on the simple log-normal stochastic process for the viscous dissipation (ϵ) “seen” along the droplet trajectory. In this paper, this model is applied in the framework of two-way coupling, wherein the turbulence generated by the spray inturn controls the spray dispersion. The criterion for the choice of one of the approaches, i.e., the stochastic drag or the stochastic forcing, follows the classical condition for drag coefficient based on the droplet Reynolds number (Re p). The non-vaporizing spray experiments from Engine Combustion Network (ECN) are used as test cases. In addition to the comparison of the spray penetration length, spreading angle and spray structure with the experimental data, a qualitative analysis of the statistics of the droplet acceleration and gas phase velocities is presented. It was shown that the new approach is much more effective in modeling the spray dynamics on relatively coarser mesh. Consequently, the new approach in the framework of two-way coupling may predict the preferential concentration effects better, which is important for spray combustion

Advanced Computational Fluid Dynamics for Emerging Engineering Processes

As researchers deal with processes and phenomena that are geometrically complex and phenomenologically coupled the demand for high-performance computational fluid dynamics (CFD) increases continuously. The intrinsic nature of coupled irreversibility requires computational tools that can provide physically meaningful results within a reasonable time. This book collects the state-of-the-art CFD research activities and future R&D directions of advanced fluid dynamics. Topics covered include in-depth fundamentals of the Navier-Stokes equation, advanced multi-phase fluid flow, and coupling algorithms of computational fluid and particle dynamics. In the near future, true multi-physics and multi-scale simulation tools must be developed by combining micro-hydrodynamics, fluid dynamics, and chemical reactions within an umbrella of irreversible statistical physics