Long flexible cylinders (e.g. risers, tendons, mooring lines) exposed to the marine environment encounter ocean currents leading to vortex-induced vibration (VIV). These oscillations, often driven at high frequencies over extended periods of time may result in structural failure of the member due to fatigue damage accumulation. Recent developments in instrumentation and installation of data acq...

This study is concerned with vortex-induced vibration (VIV) of deepwater marine risers. Riser response measurements from model tests on a densely instrumented long, flexible riser in uniform and sheared currents offer an almost ideal set-up for our work. Our objectives are two-fold: (i) we use the measured data to describe complexities inherent in riser motions accompanying VIV; and (ii) we dis...

many procedures suggest for reduction of responses of riser to vortex induced vibrations (viv). natural frequencies of marine risers is an important parameter that can affect the responses of riser to viv. change of riser properties such as top tension and bending stiffness can alter natural frequencies. in this study effects of riser specifications on the responses and fatigue damage of marine...

A brief review of recent literature on riser design is presented and a concise description of the design process is given. Effects of hydrodynamical design parameters on marine flexible riser design are then reviewed. Riser dynamic analyses are described which substantiate design criteria for the selection of riser configuration in deep and shallow water. The results of dynamic analyses using c...

With high international oil price, the exhaustion of onshore resources and declination of oil and gas production in shallow sea, deep water has become the important succeeding area of worldwide oil and gas. During deepwater oil and gas development, riser must be used to isolate seawater, circulate drilling fluid, and compensate the heaving movements of the string and so on. However, with the op...

To meet the requirements of riser safety monitoring in offshore oil fields, a new Fiber Bragg Grating (FBG)-based bundle-structure riser stress monitoring sensor has been developed. In cooperation with many departments, a 49-day marine test in water depths of 1365 m and 1252 m was completed on the "HYSY-981" ocean oil drilling platform. No welding and pasting were used when the sensor was insta...

Abstract: A method to design a boundary controller for global stabilization of threedimensional nonlinear dynamics of flexible marine risers is presented. Equations of motion of the risers are first developed in a vector form. The boundary controller at the top end of the risers is then designed based on Lyapunov’s direct method. It is shown that when there are no environmental disturbances, th...

Shrinkage defect in an alloy steel casting for marine engine cylinder cover was estimated by numerical analysis with reference to casting variables such as riser and chiller. Retained melt modulus was employed as a prediction parameter in this study. Shrinkage defects were developed at the final solidification region. This is associated with hot spots, which could be controlled more effectively...