Experimental And Numerical Studies On Dynamic Response Of Submarine Suspended Pipeline

Submarine pipelines have been more widely used with the rapid development of offshoreoil-gas exploitation. To provide theoretical foundation and scientific basis for disaster process,damage mechanism and safe assessment of submarine pipelines in an offshore environmentalcondition, investigations have been conducted on dynamic response of submarine suspendedelastic pipeline, based on model tests and numerical simulation.Dynamic response of submarine pipeline plays an important role on destabilization,strength fracture and fatigue damage. Understanding the regularity of dynamic response ofsubmarine pipeline is the basis of assessing the safe of submarine pipeline validly. In thispaper, experiments have been conducted on the dynamic response of elastic submarinepipelines suspended over flat or typical erosion beds in waves or currents of common marineenvironment for coastal or offshore submarine pipeline in service, based on the hydroelasticsimilitude criteria. A rather reasonable program and method are established for experiment ofdynamic response of submarine pipeline suspended over sea beds. The strain amplitudes andvibration frequencies are analyzed and discussed on the model pipeline over flat or typicalerosion beds in waves or currents, providing scientific basis for understanding disasterprocess and damage mechanism, and assessing safe of submarine pipelines. In the numericalstudy, three-dimensional elastodynamics equations and Morison equation are applied tosimulate the time histories of dynamic response of submarine pipelines suspended over flatbeds sucessfully. The three-dimensional interaction of pipeline and internal flow isnumerically simulated by applying the iterative computation to the fluid-structure interfacesand using the elastodynamic equation and the incompressible fluid N-S equation andcontinuity equation. Based on the numerical results, the features of pipeline dynamicresponses and internal flows are analyzed and discussed for various internal flow velocities.This method could provide a basis to study the fluid-structure interaction of pipeline andcomplex internal fluid.Dynamic response of submarine pipeline is disadvantageous for pipeline safe. Tosuppress response amplitude of submarine pipeline in an unfavorable marine environment,spoiler attachments are usually applied in practice, however, suppression mechanism ofspoilers is not completely understanded. Based on submarine pipeline spoilers,two-dimensional fluid-structure numerical investigation of cylinders with various sets of fins has been conducted by applying non-dimensional N-S equation and mass-spring systemsimplification. Arbitrary Lagrangian Eulerian (ALE) method and leader-follower method areused together in these numerical simulations, availably keeping good quality of the fluiddomain mesh for large displacements of fluid-structure interface. The vortex inducedvibration for bare cylinder and cylinders with different sets of fins is numerically simulated atlow Reynolds numbers. Vibration response, lift coefficients, drag coefficients and wakevortex mode are compared and analysed for cylinders with different sets of fins. Suppressionmechanism of the fin spoilers on the cylinder response is discussed by comparing the wakecharacteristics of a finned cylinder to those of a bare cylinder. The numerical results indicatethat configuration of fins affects wake vortex mode, response amplitude, lift coefficients anddrag coefficients. Meanwhile response amplitude has a strong relationship with the phasebetween the lift force and the cylinder motion.