Determine The Maximum Allowable Length And Study The Coupling Of The Inline-crossflow Of Pipeline

Nowadays pipelines transportation is one of the important transportation modes. Oil and natural gas are transported Almost by pipelines. However, checking and maintaining them is very discommodious. Once them are destroyed, it is difficult to repaired them. Thus analyzing their safety on the seabed is necessary.Because of the action of the force of the wave and the current, the pipelines installed on the bottom of the sea are eroded and become uncontained. Under this circumstance, they are easily occur large displacement and stress, or sympathetic vibration with the eddy. Therefore, researching and controlling the maximum allowable span length, it is the precondition of the adopting corresponding safeguard. The result is valuable in practice.Since the pipelines are spindly and easily deformed greatly under outer force even their strains aren't much, it is ill-suited to use linearity method to analyze them. At the same time, as especial construction, they have the common character of the beam and tube. So this paper uses the geometry non-linearity and beam of half-immense length theory to calculate the inter force of the pipelines. The mechanical model took the boundary conditions, circumstance and temperature into account to keep the result close to the true.A time domain model is formulated in which the in-line and cross-flow deflections are coupled through the axial tension which in turn is computed from the pipeline prolongation at any time. This formulation introduces time dependent tensions and non-linearity into the problem. Using this as the initial condition a series of calculations are carried out to examine cross-flow induced deflections induced by an in-line prescribed deflection and vice versa. Finally, an idealistic simulation of flow induced vibration is presented. The model simulations demonstrate that the coupling varies with the mode shape and with which component it is initially introduced into. However, it is evident that the coupling effects may be significant and not negligible.