해저 매설구간에서의 파이프라인 안정성 해석

초록

Offshore subsea pipelines are to be stable to external loadings which are mostly due to wave and current. To determine the stability of subsea pipeline on seabed, Morrison equation has been applied with prediction of inertia and drag forces. When the pipelines are placed in a trench, the forces are reduced considerably. Therefore to predict the stability of pipeline in the trench, the reduction factors are often employed. To investigate the stability in various trench, the flow over the trench was numerically simulated and compared with experimental data from P.I.V. (Particle Image Velocimetry) measurement. In this computation, Smagorinskys eddy viscosity model combined with a truncated deductive model is used to represent the SGS stress fields in quadrilateral structured grid system. The present results were produced at Reynolds numbers ranging from 6×103 to 3×105 based on the diameter of cylinder in the trench. Quasi-periodic flow patterns computed by large-eddy simulation were compared with experimental data in terms of mean flow characteristics for various configurations of trench (W/H=1,3,5 and H/D=2,3,4). The stability for various trench conditions is addressed in terms of mean amplitudes of oscillating lift and drag, and reduction factors for each cases are suggested for pipeline design.