Study On Hydrodynamic Characteristic Of Single Floating Box With Tensioned A Nchorage

Since the 21st century,the CPC central committee and the state council have put forward the grand goal of "Gradually Building China into a Powerful Maritime Economy".The Marine power strategy proposed by the 18th national congress regards Marine development and water transportation as an important development direction.With the development of Marine floating structures,the floating structure with tensioned anchorage is more and more widely used in marine engineering and transportation engineering,such as tension leg platform(TLP),floating bridge and submerged floating tunnel.Compared with catenary anchoring structure,tensioned anchoring structure can better limit the displacement and occupy less space,but the mooring line force is relatively large,which requires higher durability of the structure.Over the past 20 years,scholars at domestic and abroad have done a lot of researches on the hydrodynamic performance of tensioned anchorage structures.By means of empirical formula,physical model experiment and numerical simulation,these studies have achieved fruitful results in revealing the hydrodynamic characteristics and interaction mechanism of waves on tensioned anchored floating structures.However,there are still some shortcomings in the pressure and wave suppression performance of tensioned anchorage structure.In order to further study the hydrodynamic characteristics of the tensioned anchoring floating structure,this paper takes the single floating box with tensioned anchorage as the research object,studies the hydrodynamic pressure,mooring line tension and transmission coefficient of the single floating box through the physical model experiment and numerical simulation method based on the viscous flow theory.The influence of angle between anchor chain and vertical direction,pretension force and wave factors on hydrodynamic characteristics is analyzed in detail,and the relationship among hydrodynamic pressure,mooring line tension and transmission coefficient is studied by combining the flow field in the numerical model.In this paper,single floating box with tensioned anchorage is taken as the research object,and its hydrodynamic pressure,mooring line tension and transmission coefficient are studied.The research mainly includes the following parts:(1)Physical model experiment of single floating box with tensioned anchorage:The hydrodynamic characteristics and mooring line force response of 34 conditions under the action of regular waves are simulated.The experiment was carried out in a two-dimensional wave tank.By changing the angle of mooring line,the pretension of mooring line and wave factors such as wave height and period,the influence of different factors on the hydrodynamic pressure,mooring line tension,transmission coefficient and motion response of single floating box was simulated.(2)The numerical model complements the cases which were not simulated in the experiment from the aspects of mooring line inclination and pretension force.The numerical simulation is based on the theory of viscous flow,and the mooring line is regarded as a spring with certain stiffness,the stress-strain relationship is described according to Hooke's law,and the rigid body motion equation is used to describe the single floating box's motion.The results show that the numerical model can well simulate the physical model experiment.(3)According to the experimental and numerical simulation results,the hydrodynamic characteristic of single floating box with tensioned anchorage are analyzed.The mooring line inclination and pretension force are the main factors that affecting the motion response and transmission coefficient of single floating box with tensioned anchorage.For the hydrodynamic pressure on the seaside of single floating box,with the increase of the angle between the anchor chain and the vertical direction,the hydrodynamic pressure shows a trend of increasing firstly and then decreasing and finally increasing,and the hydrodynamic pressure reaches its maximum when the angle is about 30°;The hydrodynamic pressure increases with the increase of pretension force,and the effect of pretension force on hydrodynamic pressure is greater than that of wave height and period.In addition,the free surface level also affects the hydrodynamic pressure.As for the mooring line tension,it tends to increase with the increase of mooring line inclination or pretension force.And the main influence of mooring line inclination on tension occurs in the condition less than 30°,while the main influence of pretension force on tension occurs in the condition of large pretension.In addition,the mooring line tension on the seaside is more easily affected by angle and pretension force than tension on the backside.In terms of the transmission performance of floating box,the increase of mooring line inclination and pretension force have a good effect on the wave resistance performance,which means the transmission coefficient decreases with the increase of angle and pretension force.When the angle is between 30°and 45°,the transmission coefficient decreases obviously,and the influence of mooring line inclination on the transmission coefficient is greater than that of pretension force.(4)Analysis of flow field characteristics:The results of the numerical model are verified by experimental results,and studied the hydrodynamic properties combined with experimental results under different influencing factors(mooring line inclination,pretension force and wave conditions such as wave height and period)of the single floating box with tensioned anchorage.This paper analyzes the relationship among hydrodynamic pressure,mooring line tension,transmission coefficient and the flow field characteristics,which could provide design reference for the stability and durability of the floating structure with tensioned anchoring.