Studies On Non-uniform Temperature Field And Temperature Effect Of HT/HP Deep-sea Pipelines

Currently there are little research on the temperature field of the deep-sea pipeline which is laid directly on the seabed,as a result,studies on the temperature effect of the pipeline are based on constant temperature.In fact,during the process of oil transportation,the oil temperature along the pipeline will be reduced.Due to the convective heat transfer between the oil and the pipeline,the temperature along the pipeline decreases consequently.Therefore,it is necessary to carry out the study on the non-uniform temperature field and the temperature effect of the deep-sea pipeline.In this paper,the geometric model of a single-layer pipeline is established and meshed with GAMBIT,two kinds of flow state of the oil are considered,that is,the laminar flow and turbulent flow,and numerical simulation on the non-uniform temperature field of the pipeline in steady flow is conducted with FLUENT.The mesh independence is analyzed,and a reasonable method of mesh generation is adopted,and the curve of the temperature along the pipeline is obtained.Then the FLUENT model is verified by comparing the oil temperature result of the numerical simulation with that of the theoretical formula.Finally a parametric analysis on the temperature field of the pipeline is carried out.Then numerical simulation on the non-uniform temperature field of the pipeline during start-up is carried out with FLUENT.The time step independence is analyzed,and a reasonable and efficient time step is selected.Two ways of start-up are considered,that is,cold running and preheating,and the curve of the time-varying temperature along the pipeline is obtained.Then numerical simulation on the non-uniform temperature field of the pipeline during shut-down is also carried out with FLUENT.The time step independence is analyzed,and a reasonable and efficient time step is selected,and the curve of the time-varying temperature along the pipeline is obtained.The finite element model of a deep-sea pipeline is established by using ABAQUS with material nonlinear considered,and initial geometric imperfection is introduced into the model by modal analysis.A parametric analysis on the temperature effect of the pipeline is carried out considering non-uniform temperature field,initial geometric imperfection and pipe-soil nonlinear interaction,and the lateral displacement and stress of the pipeline are studied under non-uniform temperature field.