Research On The Jetting Arm Of Jetting Propelled ROV Trencher And Its Jetting Process

Submarine cable project for power transmission is a key part of the cross ocean power grid transmission project, plays an important role in the internationalization of the power grid and the process of regional power grid interconnection.To protect the submarine cable, the best way is to bury it under the ground. As to the zhoushan sea area which there are many reef on the bottom, post-trenching is the best way and the ROV trencher is the most commonly used in post-trenching. The jetting power of existing ROV trencher is lower in free fly mode than tracked mode, which makes the scour efficiency decrease. Therefore, it is very necessary for the optimization of scour efficiency of jetting propelled ROV trencher to study the influence of different factors on the scouring effect. In this paper, through theoretical deducing, small scale model and simulation analysis, analysis the relationship between parameters of the jetting arm of jetting propelled trench and the scour effect.In the first chapter, this paper mainly introduces the research background of this issue, the current research status of trencher and jetting system.According to the project requirements and the analysis of the advantages and disadvantages of all kinds of trenchers, proposed the significance and content of the research.In the second chapter, this paper proposes the methods of improving the efficiency of this kind of trencher based on the analysis of the current status of jetting propelled ROV trencher and the project requirements. And analysis the influence of the parameters of jetting on the efficiency of erosion. Combined theory of soil break and scour by jetting water, analysis the relationship between these parameters and soil break stress, sediment discharge.In the third chapter, this paper simulate the three nozzles jetting scour to analysis the influence of the scour of adjacent nozzle. This paper analysis the erosion process in detail through the distribution of velocity, pressure and suspended sediment concentration. And then analyzes the influence of change jetting distance and nozzle spacing on the influence of adjacent nozzle erosion.In fourth chapter, this paper mainly designs the small scale model of single jet scour base on the analog principle, the test is divided into static scour test and mobile scour test. In this chapter also choose the sediment type used to test and analysis its diameter distribute according to the test requirement.And then design the adjusting device,actuating device, observation system and test steps.In the fifth chapter, this paper compared the depth and width of the scour pit of simulate results and experiment results to verify the validity of the simulation. And then analyzes the influence of jetting angle, jetting distance, volume and flow rate on the effects of the scour and the self-similarity of scour profile under different scour parameters. The mobile scour tests are to analysis the scour effect of vertical jetting, oblique jetting and different angle jetting. And analysis the self-similarity of the cross section of scour pit under different jetting angle, moving speed.In sixth chapter, the main research work of this paper was summarized and and the direction to ameliorate is also brought out.