ABSTRACT

Under the actual marine environment, slender risers suffer from external ocean current and internal flowing fluid. When the viscosity of internal fluid is included, the riser’s nonlinear dynamic response is worthy of extra concern. This paper adopts a force-decomposition model to simulate VIV hydrodynamic forces, the embroil force, relative inertia force and Coriolis force induced by internal flow are included in the motion equation of marine riser. The internal fluid viscosity in essence affects the relative inertia force and Coriolis force, and its effect has to be considered. The comparable ideal flow with U_i= U_i,max/2 brings the dynamic response closer to the laminar flow case than that with U_i= U_i,max, while U_i= U_i,max/2 underestimates the fatigue damage with internal laminar flow. Generally, the internal laminar flow effect on structural cumulative fatigue damage is more significant than that on dynamic response.

摘要

在实际海洋环境下，细长立管受到外部洋流和内部流动流体的影响。当包括内部流体的粘度时，立管的非线性动态响应值得额外关注。本文采用力-分解模型模拟VIV水动力，海洋立管运动方程包括内流引起的牵拉力、相对惯性力和科里奥利力。流体内部粘度实质上影响相对惯性力和科里奥利力，必须考虑其影响。U _i =  U _{i, max} /2的可比理想流动使动态响应比U _i = 时更接近层流情况U _{i, max}，而U _i =  U _{i, max} /2 低估了内部层流的疲劳损伤。一般来说，内部层流对结构累积疲劳损伤的影响比对动态响应的影响更显着。