The innovative aquaculture equipment known as high-density polyethylene (HDPE) floating rafts has gained popularity among fishermen in the southeast coastal regions of China. Compared to deep-water anti-wave fish cages, the construction costs of HDPE floating rafts are 50% to 75% less. There is a dearth of comprehensive publicly available records of HDPE floating rafts sea trial data, despite substantial numerical studies on the motion response of aquaculture fish cages and scale model experiments under controlled-wave conditions. This study involves sea trial techniques under operational and extreme environmental conditions for motion responses of HDPE floating rafts, presents a comprehensive procedure for sea trials of HDPE floating rafts, summarizes the issues encountered during the trials, and suggests solutions. Using MATLAB for independent programming, motion videos and photos collected from the sea trials are processed for image capture, yielding the original time history curve of vertical displacement. Based on the sea trials’ data, including motion displacement, acceleration, mooring line force, overall deformation patterns, and current and wave data, recommendations are provided for the design and layout of HDPE floating rafts. Based on the Fast Fourier Transform (FFT) method for spectral analysis, the influence of interference items on the observational data is eliminated; the rationality of the observational data is verified in conjunction with the results of the Gabor Transform. This study offers a scientific analytical method for the structural design and safe operation of HDPE floating rafts and provides a reference for subsequent numerical simulations.

Sediment erosion around submarine pipelines is a popular topic, widely investigated in both ocean and submarine-pipeline engineering. In this paper, the incompressible smoothed-particle hydrodynamics (ISPH) method is modified for simulation of local scouring process around the submarine pipeline under the action of unidirectional flow. The erosion model is based on the Clear Water Particle–Turbid Water Particle–Critical Shear Stress (CWP-TWP-CSS) concept, and a sand–water two-phase model is proposed to deal with the sediment-entrained flow. The results of the numerical simulation are compared with the experimental data to verify the accuracy and applicability of the numerical model. The scouring process around the pipeline is investigated under different conditions, i.e., pipeline diameters, gap ratios, and flow velocities. The ISPH model is further used to study the flow characteristics of the scour pits around the submarine pipeline and the influence of the vortices on the maximum scour depth, to provide a theoretical basis for the stability design of submarine pipelines.

The research of quality control strategy of marine engineering using big data technology is to better promote the enterprise to reduce cost and increase efficiency. In this paper, starting from the project quality control system, a quality control risk evaluation model is constructed based on hierarchical analysis and fuzzy comprehensive evaluation by means of the fuzzy comprehensive evaluation of affiliation degree. For the model constructed based on AHP-FCR in this paper, experimental analysis of quality control influencing factors and fuzzy comprehensive evaluation examples were conducted by establishing indicators. From the influence factors, the severity of engineering personnel risk and engineering machine risk are 19.289 and 20.216, respectively, both of which are significant levels of influence. From the fuzzy comprehensive evaluation, 49.09% of the experts voted that the level of quality control risk of S Company’s offshore engineering module oilfield construction project is now low and in an acceptable state. It can be concluded that the AHP-FCR model with big data technology can realize the quality control risk assessment of offshore engineering and also provides theoretical support for companies to solve the risk.

In order to realistically simulate the flow-induced vibration of submarine oil and gas pipelines, this paper assembles a gas-liquid two-phase flow vibration device, develops a detailed and comprehensive experimental procedure, and sets the flow aperture, flow pressure, flow depth, flow direction, and gas-liquid phase apparent flow rate and other variables. According to the different types of pipelines, the multiphase flow-induced vibration of submarine oil and gas pipelines can be categorized into straight pipe vibration and elbow pipe vibration, and combined with the theoretical knowledge of fluid dynamics and the equations of motion to construct a multiphase flow-induced vibration model of submarine oil and gas pipelines and discuss the vibration mechanism of submarine oil and gas pipelines in two-phase liquid flow. Combined with the corresponding experimental parameters, the vibration phenomenon induced by gas-liquid two-phase flow in submarine oil and gas pipelines is experimentally analyzed. It is analyzed that the first-order intrinsic frequency of the submarine oil and gas pipeline is kept at 23.2 Hz when the value of the Reynolds number of the in-pipe flow ranges from 2.53 × 10 ⁴ to 1.08 × 10 ⁷ . The first-order intrinsic frequency of the submarine oil and gas pipeline monotonically decreases with the increase of the Reynolds number of the in-pipe flow. In addition, when U _l =0.4m/s, the average standard deviation of the data is only 1.114m/s² with the rise of U _g , indicating that the vibration intensity of the fluid on the subsea oil and gas pipeline increases gradually with the increase of the apparent flow velocity of the liquid phase. By analyzing the multiphase flow problem of oil and gas pipelines, this study is of great significance in improving the efficiency of oil and gas transportation.

The structural strength of the upper block of the offshore converter station is very important to the overall structural safety of the offshore converter station. Based on the standardization of the SACS model data file and the result data file, this paper carries out secondary development of the SACS model, and uses MATLAB software to write programs to extract the stress conditions of all nodes under various calculation conditions. According to the BS EN 1993-1-8:2005 standard, the structural strength of all the nodes of the upper block of the offshore converter station was checked. The calculation results show that using MATLAB to write the structural strength check software of offshore converter station can be used to check the strength of all nodes under all working conditions, which can save the calculation time and greatly improve the calculation efficiency. Through the strength check of the developed software, the nodes that do not meet the requirements of the code can be quickly found out, and the structure that does not meet the requirements of the code can be optimized until the requirements of the code are met, so as to ensure the structural safety of the offshore converter station.