Simulation And Study On Suppression Of Vortex-induced Vibration Of The Drilling Riser With Affiliated Pipes

With decades of oil and gas exploration,the onshore and offshore oil and gas resources gradually reduced,the yield is decreasing gradually,many countries have oil and gas exploration and development focus on deep(500m)and ultra deep field(1500m).Offshore drilling riser system is an important part in drilling operation,when the current flows through the riser,the riser by alternating force will produce periodic in the rear of the vortex shedding phenomenon and cause Votex-induced Vibration;when the vibration frequency and vibration frequency of the riser close,will meet the frequency of occurrence of "locking" phenomenon,caused by the strong vibration tube,increased fatigue damage once the riser,riser failure,will not only affect the normal drilling platform security,also causing heavy casualties and property losses.Therefore,it is of great significance to reduce the adverse effects caused by vortex induced vibration of the riser to ensure the safe and stable development of offshore oil and gas fields.In the offshore drilling operations,there are usually several affiliated pipelines around the riser.Affiliated pipeline as the necessary production facilities,in addition to the role of auxiliary production,but also can play a role in suppressing vortex induced vibration.Three dimensional numerical simulation was performed to study the effect of the affiliated pipes on the vortex induced vibration of drilling riser.With combination of different parameters of angle of attack ?,diameter ratio d/D,spacing ratio G/D by using the CFD technique through Large Eddy Simulation(LES).The variations of lift coefficient,drag coefficient and spectral analysis are analyzed.The study revealed that: the lift coefficient and drag coefficient of drilling riser are sensitive to the changes of the angle of attack ?.the drag coefficient CD and the root mean square value of lift coefficient CLrms decrease with the increase of the angle of attack ? and minimized in the ?=30°~45° range;The number of St used to characterize the vortex shedding frequency behind the drilling riser increases slightly with the increase of ?,but the overall stability remained in the lower value range.It is considered that the arrangement method of the affiliated pipes with the diameter ratio of d/D =0.2~0.3 and the spacing ratio G/D in the range of 0.2~0.3 is the best to suppress the vortex-induced vibration of the drilling riser.