Dimensional effect of CFD analysis for submarine landslides interactions with infinite suspension pipelines

Abstract

In this study, a computational fluid dynamics method is employed to numerically investigate the impact of submarine landslides with shear-thinning non-Newtonian fluids on infinite suspension pipelines with different diameters at various Reynolds numbers, revealing the influence of the dimensional effect between the small-scale model and the engineering prototype on impact force (i.e., drag and lift forces) coefficients. The study results show that the impact force coefficients increase to varying degrees with the pipeline diameter; the influence of the pipeline diameter on the lift force is significantly higher than that on the drag force; the minimum lift force coefficient for the pipeline diameter of 500 mm is 20.2 times higher than that for the pipeline diameter of 25 mm; and the small-scale model significantly underestimates the impact forces on the prototype, resulting in dangerous submarine pipeline designs. With increasing pipeline diameter, the slumping phenomenon clearly occurs in submarine landslides due to the gravitational potential energy and it causes a rapid increase in the head velocity of the landslide, thereby significantly increasing the impact force coefficients, especially for pipelines with large diameters. Furthermore, in gravity-free simulations, the impact force coefficients decrease with increasing pipeline diameter. This is because when the impact velocity is large and the pipeline diameter is small, submarine landslides have a high shear rate on the pipeline, resulting in high frictional stresses. Notably, the influence of dimensional effects needs to be considered to determine the velocity and shear rate of the submarine landslides around/on pipelines.