Experimental Study on 3D Scour Around an Embedded Submarine Pipeline Under Oblique Waves

Wave deformation on a sloping seabed and the incident angle of waves greatly influence local submarine pipeline scour. Most previous studies on such scour considered wave deformation but not incident wave angle. Using regular waves with an incident angle of 45 degrees, we investigated 3D scour around an embedded submarine pipeline under oblique waves in experiments. After examining wave deformation near the pipeline at different embedment depths, we analyzed how seabed scour evolved around the pipeline. Results of experiments showed that under oblique wave action, pipeline embedment depth affected wave height on both seaside and leeside of the pipeline. A 3D scour hole occurred under the pileline when the ratio of embedment depth to pipe diameter (e/D) was less than 1/4. Different forms of sand ripples also occurred on both sides as e/D changed. The embedment depth also determined the rate at which scour developed. The scour hole evolved in two distinct stages: rapid and slack. The scouring rate on the right side of the pipeline was greater than that on the left during the rapid phase, leading to an imbalance in scouring depth between the two sides.