Aplicação da técnica de fluidodinâmica computacional a escoamentos do tipo golfada em tubulações industriais

Abstract

Fatigue failures in pipelines induced by vibrations are concerning due to impacts on safety, costs, and downtime. The slug flow regime is particularly critical as it causes vibrations that can lead to failures. The Energy Institute (2008) recommends predictive techniques, such as Computational Fluid Dynamics (CFD), to prevent these failures. This article uses CFD with Ansys Fluent software to simulate slug flows in a 19.5 mm diameter "U" shaped pipeline inspired by bench tests. Six scenarios were simulated with two different meshes: tetrahedral (less refined) and butterfly (more precise). Initially, the tetrahedral mesh showed conformity with the flow regimes predicted in the literature. For more accurate analyses, two cases were simulated using the butterfly mesh, resulting in clearer contours of air pockets and more realistic air-water interfaces. As expected for transient flows, the simulations revealed a sawtooth pattern in the residual graphs, with residuals converging to acceptable minimum criteria. Dynamic pressure monitoring points revealed pressure fluctuations when air pockets reached the monitoring points, with greater fluctuations observed in the pipeline curve due to changes in flow direction. Additionally, these pressure fluctuations were consistent with RAEDER (2012) data, varying according to void fraction and flow regime.