INSTABILITY OF ANGLED PIPELINE ARISING FROM INTERNAL FLUIDS FLOW

Abstract

In this study, the instability behavior of angled pipelines conveying fluid isinvestigated by using three-dimensional finite element method. Several parametersthat affect the dynamic characteristic have been studied extensively such as pipelengths ratio, diameters ratio, frame angle, inlet fluid velocity, inlet fluid pressure, andpipe thickness. Taking into account the Coriolis force, force that conforms fluid to thecurvature, and axial tension forces; the natural frequency of an angled pipeline fixedin both ends is studied. The derived element matrices include the mass, stiffness,contradictory and damping. The study found that increasing the obtuse angle leads todecrease the frame critical fluid velocity. For each formed pipeline angle, there wasan optimal frame diameters ratio that gives maximum inlet critical velocity of flowingfluid. A relatively small increase in frame frequency is obtained when increasing theinlet fluid pressure. Besides that, there was a perfect pipe thickness for each fluid flowvelocity that gives rise to get the extremely dynamic characteristic.