Optimization design of a honeycomb-hole submarine pipeline under a hydrodynamic landslide impact.

Submarine pipelines are likely to be impacted by frequently catastrophic landslides, resulting in broken pipelines and causing irreversible economic losses; however, because pipelines located in deep-sea environments are simply laid atop the seabed, effective protective measures have not yet been proposed. In this paper, a pipeline with a uniform distribution of honeycomb holes on the surface, namely, a honeycomb-hole submarine pipeline, is discussed and optimized in detail. A computational fluid dynamics (CFD) approach is verified and improved several times and then applied to conduct 120 numerical simulations for 12 types of suspended submarine pipelines under 10 conditions covering the Reynolds number range required by the project conditions. First, the typical characteristics of the impact forces acting on pipelines in a seawater environment are systematically investigated, and the peak drag force is isolated as the most dangerous load caused by a landslide impact. Second, according to the formation and reduction mechanism of the drag force, it is proposed that a honeycomb-hole submarine pipeline can effectively delay the separation of the boundary layer, reduce the impact velocity, prolong the arrival time, and decrease the differential pressure drag force. Finally, two normalized parameters, the depth ratio and area ratio, are established to develop an optimization design methodology, and the optimal design values of honeycomb-hole pipelines are achieved under the support of limited data. This work presents a protective technology for submarine pipelines and provides new insights into the response of fluid-structure interactions. [ABSTRACT FROM AUTHOR]