Experimental investigation on the nonlinear dynamic responses of the coupled floating submerged artificial seabed-mooring system in internal solitary waves

Abstract

A new deepwater artificial seabed (DAS) production system is developed as a competitive offshore field development solution in deep and ultra-deep waters. This paper experimentally investigates the acting mechanism of ISWs on the nonlinear dynamic responses of the coupled floating submerged artificial seabed-mooring (ASM) system in a large-scale density-stratified flume. A compositive method for measuring and analyzing the interactions between the ASM system and the ISW is proposed. On this basis, the spatio-temporal features of the dynamic motion responses, the mooring tension variations and the flow field surrounding the ASM coupling system are characterized. The minute motion responses of the test model are captured by a charge-coupled device camera and subsequently processed using a developed image processing method. The temporal tension variations in the mooring lines are measured utilizing a non-contact optical measurement technique. The fluid-structure interaction characteristics between the flow field and the test model are revealed through the particle image velocimetry technique. In addition, the effects of crucial environmental factors on the nonlinear coupled dynamic responses of the ASM system are systematically explored in the experiments. The results indicate that the nonlinear dynamic responses of the ASM system in ISWs are characterized by the significant surge motion (maximum: 14.7% of the water depth), the coupled heave motion with the surge response, and the considerable mooring tension variation (maximum: 31.8% of the pre-tension), especially with the test model located within the density pycnocline.