Análise em fluidodinâmica computacional do escoamento Core-Annular Flow em riser flexível com petróleo ultraviscoso

Despite advances in the investigation of core-annular flow (CAF), studies assessing the behavior of this flow regime in buoyancy-supported flexible risers, whose curved geometry can significantly affect flow dynamics, remain scarce. To address this gap, this study analyzes oil-water multiphase behavior during the transport of ultraviscous oil by using OpenFOAM to simulate this flow regime inside a riser. The study aims to investigate the hydrodynamic mechanisms that influence oil-core instability in complex geometries, thereby contributing to the safe and efficient application of this technique in real production systems. The methodology followed standard procedures commonly used in Computational Fluid Dynamics simulations. The geometry and computational mesh were developed using SALOME-MECA. The interFoam solver was employed to solve the transport equations, and the results were post-processed using ParaView software. The simulations revealed the accumulation of ultraviscous oil downstream of the positive-curvature section of the riser, owing to the high inertia of the fluid, which resists changes in trajectory. This accumulation increased flow resistance and was associated with a pressure decrease from 4,148.0 Pa to 3,365.8 Pa. In the suspended section, significant vortex formation was observed due to the high velocity gradient, potentially leading to oil dispersion into the water phase. These instabilities may generate hydraulic vibrations that can compromise the structural integrity of the system. Overall, the simulations enabled the identification of interfacial dynamics, highlighted the challenges associated with curvilinear geometry, and provided technical support for adapting the core-annular flow technique to production systems with nonlinear trajectories.