An experimental study of seabed responses around a marine pipeline under wave and current conditions

Numerical Modeling of Seabed Response to Combined Wave-Current Loading

“…Based on the numerical results, it is concluded that (1) waves with a shorter period or greater height lead to stronger wave attenuation and smaller values of maximum pore pressure and liquefied depth; (2) The waves traveling with the following current lead to an increase in wave length and reductions in wave height, maximum pore pressure and liquefied depth. However, the waves are shortened and steepened when traveling against the current, resulting in larger values of maximum pore pressure and liquefied depth.…”

“…(1) (2) in which Xi is the Cartesian coordinate, («,) is ensemble mean velocity component, ; is time, Pf is fluid density, (p) is fluid pressure, ¡1 is dynamic viscosity, and g is acceleration due to gravity. The incompressible fluid motion due to wave-current interaction can be described by the RANS equations, mass conservation and momentum conservation equations.…”

“…Under certain combinations, the wave-current loadings can result in excess pore pressure and diminishing vertical effective stress, and part of the seabed may lose its stability and become liquefied when vertical effective stress vanishes [1,2]. Their combined loading will further induce a significant fluctuation of pore water pressure and effective stresses within a porous seabed.…”

Scour depth under pipelines placed on weakly cohesive soils

“…following [22] and [28]. Dimensionless numbers describing the hydrodynamics around the pipeline can be derived from the variables appearing in (2): (i) the Reynolds number Re = U wc A bed / , based on both the wave-current velocity combination and the particle orbital amplitude at the seabed A bed , (ii) the Keulegan-Carpenter parameter KC = U wc T/D, based on the wave-current velocity combination, the wave period and the pipeline diameter, and (iii) the Froude parameter F = U wc / gh, still based on the wave-current velocity combination and the water depth.…”

“…A second experiment, carried out in the wave flume of the laboratory of Shengli Petroleum Manage Bureau (China) and described in [25] and [28] (hereafter XU10 and ZH11, respectively), aimed at investigating the soil behavior around a pipeline that was either half buried or resting on the seabed. The authors defined the tested soils as sand (d 50 = 0.287), sandy silt (d 50 = 0.057) and silt (d 50 = 0.034), each characterized by a specific clay content.…”