Characteristics of flow-induced structural effects in bent pipes

Abstract This numerical study investigates the association between flow pressure, shear stress, and the equivalent stress distribution of solid shell for bent pipes with varying bend angles (20° ≤ θb ≤ 80°) and radius (2D ≤ rb ≤ 4D). The two-way coupled effects of fluid–structure-interaction (FSI) are specifically modeled and evaluated at Reynolds number of Re = 20, 000. Distribution of flow-induced forces is primarily governed by the growth of primary and secondary Dean vortex pairs, which coincides with a corresponding velocity deficit caused by flow separation near the bend outlet. Bend angle shows a stronger association with forces compared to the variation in bend radius, such that increasing the former enhances and accelerates the formation of symmetric Dean pairs. This coincides with intensified pressure drop in the pipe, and reduced flow-induced wall shear stresses. The coupled effects and their localized concentrations further reflect a unique association with structural stress distribution on the solid shell. Bifurcations in profiles of structural stress coincide closely with locations of interactions between secondary Dean vortex pair and pipe walls. However, simultaneous impact of flow-induced moments and fixed ends of the solid shell contribute to a reversal in trends of peak stress magnitudes with increasing bend angle. This study provides insights into FSI behavior in bent pipes to improve reliability and structural integrity of pipeline design.