In this paper, the stress of temporary structures during the construction of offshore structures is analysed through the study of the temporary buried drilling platform. Firstly, The fluid flow is controlled by the modified RANS equation (the Reynolds-average equation) and Forchheimer saturation resistance model, the free surface is tracked by volume of fluid (VOF) method, and the κ–ε closed equation is solved. The finite element numerical simulation software is used to establish a multi-factor coupling calculation model of the stress of temporary buried offshore structures. The maximum wave force of temporary structures under different buried depths, different structural sizes, different load periods and amplitudes is simulated, and the stability of Long Yuan wind turbine pile foundation drilling platform under the maximum wave force is analyzed. The research results of this paper can be used for dynamic design and analysis of wave load conditions, structural design dimensions and load periods in the engineering design of embedded offshore structures in shallow water under wave loads, so as to calculate the wave load values of structures reasonably and provide concrete theoretical basis for the establishment of offshore systems.
Most existing research uses experimental designs for testing, which cannot efficiently analyse the migration and sorting rules of particles in the disturbed slurry. Therefore, based on the fluidized bed flow film theory, a slurry flow film structure system is established according to the disturbance state of the fluid. On this basis, the particle size and distribution law of the disturbing force formed by slurry disturbance are analyzed, and the calculation model of single particle lift in the flowing film is also analyzed. On this basis, using Markov probability model, the probability of particle lifting and sorting between layers is theoretically deduced. Then, according to the particle ratio of the original mud, the settlement gradation of the particles in the disturbance is analyzed. It can also predict the separation degree of particle in natural turbulence, fluidized beds, and sludge mechanical dewatering. Finally, according to the particle flow software PFC (Particle Flow Code), the main influencing parameters (disturbing force and gradation) were verified and analyzed. The results show that the particle flow simulation results are in good agreement with the calculation results. The model of slurry membrane separation proposed in this paper can provide a basis for studying the mechanism of slurry disturbance separation and particle deposition.
This paper focuses on the sorting pattern of silt deposited at estuaries under artificial disturbance based on the concept of bidirectional concealment, which is introduced for such silt with similar particle size, low disturbance exposure angle, and difficult sorting. By establishing the relationship among the absolute concealment (Δi), the drag force coefficient ($${C}_{\mathrm{D}}$$ C D ), and the lift force coefficient ($${C}_{\mathrm{L}}$$ C L ) of highly concealed silt particles under disturbance and considering the concepts of disturbance intensity, disturbance direction, and particle concealment degree, the contribution equation for the effective depth (Y) of artificial disturbance in the deposited slurry is introduced, and the mechanical equation for the internal disturbance of silt is established. On this basis, the motion initiation probability for fine particles ($${\varepsilon }_{{d}_{i}}$$ ε d i ) is calculated using the Shields parameter ($$\Theta$$ Θ c), and the theoretical model of plastic sandy silt sorting under artificial disturbance is derived from the Markov chain-based three-state transition. The method proposed in this paper can explain the bedload gradation of sandy silt under internal physical disturbance. The calculated data in this paper agrees well with that of the flume test on uniform sandy silt and the related sediment particle theories. Therefore, the clay particle transport pattern model in slurry under artificial disturbance based on the bidirectional concealment degree can explain the gradation changes of flow-plastic sandy silt under artificial disturbance, thus providing a theoretical basis for the research on the sorting of flow-plastic sandy silt under artificial disturbance.
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