Experimental investigation of internal solitary wave loads on artificial seabed

Abstract

The Next Generation Subsea Production System (NextGen SPS) is an innovative design for oil and gas production in ultra-deep ocean. As the most ingenious and significant part of this system, the artificial seabed (AS) is located at a certain depth under Mean Water Level (M.W.L) to avoid loads of conventional surface waves and surface currents. However, the strong shear currents, huge energy and enormous loads caused by internal solitary waves (ISWs) pose a threat to the security of the AS. Therefore, it is essential to study the loads of ISWs exerted on the AS. In the present paper, a number of laboratory experiments were conducted to compare the experimental and theoretical profiles of ISWs, and obtain the variation characteristics of the loads on the AS model. The effects of the ISW amplitude, the submerged depth of the AS model and the thickness ratio (TR) of the upper and lower layers (ULLs) of fluid on the loads acting on the AS model were discussed separately. The experimental results indicate that with the increase of the ISW amplitude, the maximum values of the horizontal force, vertical force and moment increased correspondingly. Under the condition of constant ISW amplitude, the maximum horizontal force is greater than the maximum vertical force, and the growth rate of the horizontal force is also higher than that of the vertical force. The horizontal force exhibits two peaks when the vertical position of the AS model is close to the pycnocline, and the difference between the peaks becomes smaller as the submerged depth of the AS model increases. Besides, the vertical force is more sensitive than the horizontal force and moment when the submerged depth of the AS model changes. The findings of this article can clearly reveal the action mechanism and load characteristics acting on the AS of ISWs, and provide necessary reference for the security of designing AS.