Abstract: In response to the issue of material tank strength failure induced by ocean loads on the first offshore fracturing ship, this study systematically conducts a fluid-structure interaction analysis of this specialized marine equipment under real sea conditions. A three-dimensional simulation model of typical material tanks and their supporting structural components is established, enabling the integration of internal flow field with fluid-structure interaction calculation. Based on indoor large-scale pool experiments, ship acceleration data under different sea conditions are determined to simulate the effects of ocean loads. The study found that as the wave spectral peak periods increases, both deformation and stress within the tank gradually rise. Additionally, with greater wave height, the stress and deformation show an upward trend. The maximum deformation and stress occur when the wave direction angle is at 90°. Moreover, greater filling ratio and increased liquid density also leads to higher deformation and stress levels. The analysis identified that the point of highest frequent maximum stress during the swing of the fracturing ship is located at the bend in the middle area of the tank wall bottom. The study found that the most critical extreme working conditions for the material tank structure are a liquid density of 1.35 g/cm$^3$, a wave direction angle of 90°, height of 4 m wave spectral peak periods of 13.00 s, and filling ratio of 95%. By accurately identifying the bend at the tank wall bottom as a critical hazard zone and outlining the most dangerous combination of extreme conditions, the research provides significant theoretical insights and data support for the design of material tank structure parameters during the swaying of the first offshore fracturing ship.

Key words: offshore hydraulic fracturing, material tank, fluid structure coupling, vibration characteristics, stress concentration