Abstract:Submarine pipelines, as important channels for transporting underwater oil and gas resourc es, offer advantages such as convenient production and installation, long transportation distances, and high transportation efficiency, and are widely used in marine oil and gas engineering. This study used Computational Fluid Dynamics (CFD) to investigate the impact of submarine debris flows on suspend ed pipelines under a suspended height equivalent to the pipeline diameter. The impact of the debris flows on the pipelines was studied by refining the mesh near the back impact side of the pipelines to capture vortex shedding during the debris flows' collision with the pipelines. The necessity of using a refined mesh model to simulate the pipelines' forces during the embedding stage was discussed. The numerical simulation results showed that the refined mesh model could more accurately simulate the normal and vertical forces on the pipelines under the conditions of high Reynolds numbers. Specifical ly, for the normal force on the pipelines, when the Reynolds number was less than 113.05, the peak normal force was the same as the peak force during the initial impact stage. When the Reynolds num ber exceeded 113.05, vortex shedding caused the peak normal force to occur during the embedding im pact stage. For the vertical force on the pipelines, a certain periodicity was observed during the impact process. Within the simulated Reynolds number range (21.89-317.08), the peak vertical force on the pipelines always occurred during the embedding impact stage. As the Reynolds number increased, the peak vertical force could be more than 5 times the initial peak value. Based on the calculated data, ex pressions for calculating the normal and vertical peak force coefficients under the conditions of different Reynolds numbers were obtained. The patterns and formulas obtained in this study are crucial for fully evaluating the impact process of debris flows on submarine pipelines.
