The six-degree-of-freedom (6 DOF) motion of the mother-ship, which is caused by wave fluctuation, makes offshore operations difficult. To solve this problem, various heave compensation systems were proposed, as well law motion. These included passive system, semi-active and active (AHC) system. However, empirical formula not suitable for practical operations, rare AHC take characteristic into c...

With the increase of ship size, stiffness hull structure becomes smaller. This means that frequency wave excitation tends to be closer natural vibration, which in turn makes hydroelastic responses more significant. An accurate assessment loads and motion hulls is key design safety assessment. In this paper, coupled CFD (Computational Fluid Dynamics)-FEM (Finite Element Method) method used inves...

We used field observations of frost-boil distribution, soils, and vegetation to attempt to validate the predictions of a Differential Frost Heave (DFH) model along the temperature gradient in northern Alaska. The model successfully predicts order of magnitude heave and spacing of frost boils, and can account for the circular motion of soils within frost boils. Modification of the model is neede...

In order to evaluate the efficiency of heave compensation in the Ocean Drilling Program, we developed a device measuring the acceleration of the core barrels. First results show that heave compensation limits bit motion to 10% of the surface heave. We also use the acceleration data to characterize the formation. On rotary corers, acceleration amplitudes decrease with increasing hardness of the ...

Original scientific paper The floating cranes, which transfer payloads during offshore constructions, need meet rigorous demands for efficiency and safety in serious sea conditions while the unexpected motion of the floating crane caused by wave make it even harder. This paper analyses the dynamics of a floating crane and presents an active heave compensation system (HCS) to allow the payloads ...

To compensate for heave motion, which has an adverse impact on the response of a drill-string or a riser, passive and active devices are usually used. Active heave compensators, whose control system is an essential part, allow conducting operations under more extreme weather conditions than passive ones. This paper presents a constructive method to design a nonlinear controller for an active he...

The existence of a moonpool may affect motion characteristics and stability drillship. This paper presents numerical experimental study on the influence configuration performance drillship under condition constant displacement. Ship hydrostatics three-dimensional (3D) potential flow theory are employed to calculate static curves (GZ curves) response amplitude operators (RAOs) with conjoined dou...

We solve the problem of cargo transfer in high sea states over a ramp from a large, medium-speed, rollon/roll-off (LMSR) vessel to a smaller connector vessel of a surface effect ship (SES) type. Our aim is to reduce rampmotion between the LMSR and SES in order to provide a safer environment for cargo transfer. We design an air cushion actuated controller to estimate and cancel the wave disturba...

This work extends the previous effort in unsteady Reynolds averaged Navier-Stokes (RANS) simulations developed by the ship hydrodynamics group of the University of Iowa Iowa Institute of Hydraulic Research to the capability to predict pitch and heave motions of ships with forward speed in regular head seas. The simulations are performed with CFDSHIP-IOWA, which is a general-purpose, multiblock,...

In active heave compensation, in order to realize the smooth control of compensation platform, it is necessary use ship motion measurement system accurately obtain displacement signal, invert and then expansion contraction electric cylinder so that platform remains horizontal. The generally adopts second integral acceleration sensor signal. During acquisition process quadratic integration accel...