Dynamic Response of Risers Conveying Fluid

Abstract

Riser conveying fluid is one category in a wide research area known as moving continua dynamic that was the subject to many research studies in the past 50 yr. The structure investigated in this paper is assumed to be a flexible pipe having a geometry of a simple catenary with a buoyancy force at the top. The riser is modeled as a beamlike continuous system subjected to wave, current, and wind forces. The derivation of the partial differential equation of motion included the following aspects: nonlinearities due to geometry, i.e., large displacements as well as wave drag force, fluid internal and external pressure, and internal fluid velocity and acceleration. The wave forces are approximated via Morison’s equation, where the drag force is proportional to the square of the relative velocity between the riser and the waves. All forces are calculated at the instantaneous position of the riser, causing the equation to be highly nonlinear. The nonlinear partial differential equation of motion is then solved numerically. Finite difference approximation code that was imbedded in ACSL software is used. The equation of motion is solved to evaluate the riser’s response to different environmental conditions and other physical parameters such as internal pressure and fluid velocity and acceleration. [S0892-7219(00)00203-X]