Numerical and Experimental Study of Offshore Pipeline Stability in Trench

Abstract

Offshore pipelines are to be stabilized against external loading caused mainly by wave and currents. When pipelines are placed in a trench, the forces acting on them are reduced considerably. To investigate the stability in various trench sections, the flow over the pipeline is numerically simulated and compared with experimental results obtained from particle image velocimetry measurement. This paper consists of two parts: single pipe and dual pipe in various trench sections. Each part compares numerical results with experimental results, which include mean flow pattern, drag-force coefficient, and lift-force coefficient. For a single pipe, Smagainsky’s eddy viscosity model combined with a truncated deductive model is applied to represent the stress field in a quadrilateral structured grid system. In the numerical simulation for dual pipes, the Navier-Stokes equation and elliptic mesh generation method are used. The stability of various trench conditions is addressed in terms of mean amplitudes of oscillating lift and drag and reduction factors for each case. The results can be effectively applied to pipeline design.