定常流中不同淹没深度下水平圆柱载荷分析

基于CFD方法的数值模拟对水平圆柱与定常流相互作用的问题进行研究,首先建立含有自由液面的定常流条件下固定与刚体运动圆柱体的二维数值计算模型,在建立的模型中分别对不同淹没深度、不同流速、不同圆柱尺寸、不同雷诺数下水平圆柱的载荷进行分析计算.结果表明：随着圆柱淹没深度的增加,圆柱受力先增加后减小;靠近自由液面时,淹没深度是影响受力的重要原因,其中水平系数对淹没深度的敏感程度比垂向系数小,主要是由自由液面波动引起的反射和阻塞所导致;S/D<-2.5(S为圆心到水平面的距离,D为圆柱直径)时可以忽略自由液面的影响,固定与刚体运动圆柱体均在S/D=-1时水平系数达到最大,S/D=-0.5时,垂向系数达到最大;随着雷诺数的增加,运动圆柱水平系数平均值先增再减,垂向系数平均值不断减小.     

Fatigue sensitivity analysis of steel catenary riser near touchdown point

By transforming the platform response obtained from coupled hydrodynamic analysis to the top motions of steel catenary riser (SCR), the nonlinear dynamic analysis of the SCR is carried out in Abaqus/Aqua. In this analysis, the SCR-seabed interaction is well taken into account by introducing the seabed trench model and hysteretic seabed model. The fatigue damage of the SCR near touchdown point (TDP) is calculated using rain-flow counting methodology, and the sensitivity of the fatigue damage to the seabed and wave parameters are investigated. The results indicate that as seabed stiffness increases, the fatigue life and its sensitivity to seabed stiffness decrease. Seabed trenching may benefit the fatigue life of the SCR and the trench position should be elaborated for realistic fatigue damage prediction. Due to the induced platform response, significant wave height and spectral peak period have significant effects on the fatigue damage, thus the short-term sea state bins should be carefully selected from the wave scatter diagram.