# Scaled Model Simulation and Experimental Verification of Submarine Flexible Pipeline Laying System
## 1 Introduction  
The submarine pipeline is one of the most widely used modes for offshore oil and gas transportation, which has obvious advantages in efficiency, economy, and reliability. Compared with rigid pipelines, the flexible pipeline will become the main form of submarine pipeline development due to its obvious advantages such as high-speed laying, seawater corrosion resistance, bending, and tension resistance. The efficiency of submarine pipeline laying will become a hot issue in marine energy transportation [1, 2, 3, 4, 5]. Compared with land pipelines, the laying process of submarine pipelines needs to consider complex adverse factors such as current and wave. Main laying methods include S-laying, J-laying, and recently developed flexible laying [6]. In the study of coupling dynamic characteristics between piping system and piping of ship, pipe-laying tower and other equipment, the solution of the theoretical mathematical model has certain limitations. Therefore, it is necessary to verify the dynamic characteristics of the pipe-laying system by model tests. For the dynamic characteristics of pipe-laying vessels, many scholars have carried out model tests on the hydrodynamic responses of ship models with different proportions under the influence of wind, wave, and current coupling to study the operation of pipe-laying vessels. Traditional tank model tests can test and study ship displacement, acceleration, the amplitude response operator (RAO), additional mass, and other data. The tremendous increase in modern computer computing power has enabled researchers in the field of wave energy to simulate various sea conditions and study the operation of layingvessels [7; 8; 9]. However, a small error will cause considerable errors in model building, instrument measurement, and environmental load simulation. The study of deep-sea pipeline-laying systems also requires dynamic analysis of pipelines in laying. [PERSON] [10] analyzed the bending moment distribution of the pipeline during the laying process by using the finite element model according to the pipe-laying project in the Black Sea. [PERSON] [11] established a rigid finite element model for the pipeline mechanics in the process of pipeline laying and studied the influence of the horizontal distance between the pipeline bottom contact point and the ship and the movement with the pipeline on the tension of laying equipment. [PERSON] [12] established a mathematical model through the concentrated mass method to analyze the dynamic tension and failure load of the cable. In order to analyze the influence of riser platform on pipe laying, [PERSON] [13] established the balance equation of flexible pipe from the perspective of vibration sensitivity of flexible pipe, obtained the relationship between riser buoyancy and riser axial force through analysis and solution, and verified the conclusion through experiments. [PERSON] [14] has conducted an in-depth exploration of pipes with honeycomb holes. [PERSON] [15] established a fine finite element model considering the complex surface contact behavior of the curve section under the framework of ABAQUS. [PERSON] [16] proposed a coupled time-domain numerical model to study the influence of coupled dynamic response. The coupling model considers the motion of the pipe-laying ship, surface wave, ocean current, wind force, pipeline dynamics, and the contact between the roller and the pipeline. Proportional, integral, and differential (PID) controllers are used to simulate the control of pipe-laying ships. [PERSON] [17] simulated the 352.42 mm outer diameter flexible pipeline laid on the 3000 m deep-sea bed by using Orca flex software under specific sea conditions and studied the dynamic characteristics of axial tension, bending moment, stress, and strain during pipeline laying. The scaled model test can provide data to guide the modification and implementation of the design plan of the lay-up system. During the test, we will understand the various phenomena and rules in the structure more intuitively.