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Hang-off mode of a drilling riser is occasionally needed during subsea installation/platform relocation operations or evacuation after an emergency disconnection. A suspending riser without any restriction at its bottom is more flexible and more dangerous in complex sea states than a connected riser with excess axial tension. Internal solitary waves (ISWs) can particularly exert a sudden impact and shearing force on risers, and vessel motion can expand horizontal dynamic responses of the risers. In this paper, considering vessel motion and the combined excitation of ocean currents, surface waves and ISWs, a dynamic model is constructed based on the Euler-Bernoulli theory, in which ISW is simulated by the Korteweg-de Vries (KdV) equation with a two-layer seawater model. Then, the structural governing equation is numerically solved by the Wilson- method and preconditioned generalized minimal residual method (GMRES) with a self-developed MATLAB program. Case calculation shows that ISW can largely increase the envelopes of riser properties in the upper seawater layer and dramatically expand the horizontal deviation of the bottom of a hang-off riser during ISW spreading. Particularly, the dynamic responses of a riser will be larger with ISW amplitude augmentation, and larger with an increase in the density difference between the two seawater layers. In addition, vessel motion can increase the horizontal deviation along the entire length of a riser with a range that is nearly the same as that of the vessel motion amplitude, and increase the envelopes of bending moment and shearing force at the lower section of the riser near the riser bottom. Therefore, limiting the vessel motion amplitude, optimizing the vessel towing speed, maintaining a lower marine riser package (LMRP) at the riser bottom to strengthen axial tension, and using slick joints with larger wall thicknesses in the upper depth may be effective engineering considerations. More importantly, much attention should be paid to avoid the riser bottom/LMRP striking other subsea equipment in oceans in which ISWs occur frequently.

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In the ethylene industry, the high purity of the ethylene product depends on hydrogenation in acetylene hydrogenation reactor. Because the catalyst deactivation leads to the moving of the operating point, the operation scheme must be adjusted continually according to the catalyst activity. It is necessary to estimate the catalyst activity online. Based on the discrete dynamic model of the acetylene hydrogenation reactor, the extended Kalman filter (EKF) is used to build the soft sensor for catalyst activity. Considering that EKF involves the large computation costs, we propose a method that estimates the parameters of the time‐varying deactivation kinetics model for the tradeoff of accuracy and complexity. The method is effective to reduce computation complexity of estimation, and simultaneously, the accuracy satisfies the process requirement.

The shape and size of the linked polymer microspheres and the matching between the microsphere size and nuclear-pore membranes were studied in this paper. Scanning electron microscopy(SEM), microscope, dynamic lighting scattering(DLS), Laser diffracting measurements, nuclear-pore film filtration and sand packed tube displacement experiment was adopted for investigation. The results showed that the original shape of the microspheres is typically spherical with a size range of 400-5000nm. When the microspheres were dispersed in water, swelling occurred, resulting in larger size but spherical conformation remained. And the system was poly-dispersed. There are certain matching relationships between the microsphere size and the membranes pore size, and the best plugging property could only occur when they are well-matched. Matching relationships also exist in the sand packed tube displacement experiment, when sand packed tubes with low permeability were used, plugging could occur effectively, and well in-depth plugging could happen as well.

In marine floating drilling, emergency disconnection of a drilling riser is required in harsh environments or loss of dynamic positioning control. After disconnection, drilling mud in the riser discharges directly from the riser bottom, and seawater refills the vacancy emptied out after mud falling through refill valves. This paper presents two new simulation procedures for this unsteady flow. The first one is a whole fluid column(WFC) model and it is solved by a cubic equation. The second one is a computational fluid dynamics(CFD) procedure, in which two high-resolution CFD schemes are applied for the first time to discrete a special governing equation, and Level Set method is adopted to track the interface between mud column and refilled seawater at each time step. Two methods can respectively provide variations of flow velocity, fluid pressure, whole column weight and flow friction force in a whole mud release duration. In particular, WFC method can easily predict overall trends of several parameters during a whole discharge period, which are prerequisite parameters for dynamic analysis of a riser in hanging state; CFD method is very sensitive to every detailed fluctuation of velocity and pressure in the initial moment of mud discharge, and can be integrated into a structural model for riser recoil response analysis. For a drilling riser with 2150 m, it takes 195.83 s to replace all mud column by seawater, and the maximal discharge velocity is 14.61 m/s. During mud falling, the top of mud column keeps static for 2.29 s before the first pressure wave reaches, and fluid pressure of part column section drops to zero and lasts 1-3 s. In addition, the maximal values of fluid weight-loss and friction force are both close to half of the whole column weight. These results are beneficial for riser system design and risk control of riser recoil.

In recent years, there have been frequent leakage and explosion accidents caused by the cracking of the circumferential weld of buried pipelines, and soil subsidence is one of the main reasons for the accidents. This paper carries out a numerical simulation analysis based on the soil spring model of the buried pipeline, and studies the mechanical response laws such as axial stress and deformation of buried pipelines under different subsidence ranges. The results show that: With the increases of the subsidence range, the deformation of the pipeline first gradually increases, and then remains unchanged, the axial stress of the pipeline, first increases, then decreases slightly, and finally remains unchanged. With the increase of soil subsidence amount, the dangerous subsidence range of soil increases. When the subsidence amount reaches the yield displacement of the soil, with the increase of subsidence range, the maximum axial stress of the pipeline increases. The results have certain guiding significance for the design and maintenance of buried pipelines.

Aiming at the problem that there is no effective tool to quickly analyze the mechanical response of long-distance buried pipelines, this paper uses the APDL language of ANSYS to compile a rapid solution program for the mechanical response of buried pipelines based on the soil spring model. The program is used to establish the calculation model of 500 m long pipe, and analyze the mechanical response of the pipeline with and without medium and subsidence. The value are compared with those of ABAQUS based on PSI unit and solid contact model. The results show that the calculation value of these three methods are in good agreement. The program can realize rapid modeling and accurate analysis of long-distance buried pipelines, and has high engineering application value.