Mesh influence on the modeling of the flow around underwater risers with the use of computational fluid dynamics (CFD)

Abstract

Submarine pipelines are used in offshore well drilling and production of oil and natural gas operations. These products can be flat on the seabed with the function of transporting oil from a production well to a floating production unit on the surface sea (oil platform). They are called submarine pipelines or flow lines when resting on the seabed and when the pipeline is suspended, linking the seabed to the production unit on the surface, they are called risers. These products are subject to sea currents, waves and movement induced by the floating unit to which they are connected. Their interaction with sea water produces two power components in the pipeline: the drag force (FD) and transverse (FL), respectively, in incidence and perpendicular in relation to the water duct. The transverse force is the pipe oscillate in the direction perpendicular to the incidence rate of the fluid, a phenomenon known as Induced Vibration for Vortex (VIV), in synchronization with the shedding of vortices. This vibration is important for the design of pipelines, as it may accelerate the duct fatigue process, causing failures. This work will be applied to Computational Fluid Dynamics (Computational Fluid Dynamics - CFD) to solve the three-dimensional flow around a section of a submarine pipeline. We considered the existence of two situations: the first being the stationary section of the duct; and second is the section with a forced movement induced in the transverse direction to the incident flow. In both cases, many situations will be simulated with different impact speeds. Hydrodynamic drag coefficient (DC) and lateral force (CL), as well as the Strouhal number (St) for the flow are calculated with some comparison and analysis of results with literature. (AU)