STUDY OF FLOW AROUND A CIRCULAR CYLINDER - INFLUENCE OF REYNOLDS NUMBER AND TURBULENCE INTENSITY

Resumo

Flexible risers, widely used in offshore engineering, are long multilayer tubes designed to
carry fluid — such as oil and natural gas — from the seabed to the sea platforms. In this scenario, the
risers have to be able to withstand efforts ranging from their weight, water column pressure, to dynamic
loads resulting from sea currents. This study aims to evaluate the influence of sea currents on flexible
risers. For this interaction, the fluid passage was evaluated in a uniform flow around the cross-section of
the tube in a two-dimensional analysis. The seasonality and variation of sea currents over time make it
necessary to study different flow regimes. This phenomenon generates pressure variation on the surface
structure, causing dynamic efforts that can induce oscillations, increase drag force and cause structural
failure if the frequency of vortex shedding approaching one of the natural frequencies in a structure.

Therefore, the drag and lift coefficients and Strouhal for Reynolds numbers in the laminar and turbu-
lent regime are so important. They are obtained through modeling using computational fluid dynamics

software, ANSYS

R Fluent, and then compared with the results of other models in the literature. In the
case of the k − ω SST turbulence model simulations, it is used fixed turbulence intensity values for all
Reynolds numbers. This work intends to vary this parameter in order to verify its influence in some
aerodynamics coefficients, taking into account the Reynolds number.