Design And Optimization Of Test Buoys In Offshore Marine Instrumentation Test Field

As China's strategy of"adhering to the overall planning of land as well as sea and accelerating the construction of marine power"continuously advances to meet the demand for high-precision marine monitoring equipment,the strategy is bound to promote the development of related offshore marine instruments.However,the lack of low-cost,highly reliable,and easy-to-use test platform for examing instruments delays the development process and conversion efficiency of China's related equipment,and intensifies the contradiction between supply and demand for precision offshore monitoring instruments in China.In order to meet the requirements of the national developmentary policy and promote the construction of China's offshore marine instrumentation test field,this research designed and optimized the test buoy in the offshore test field based on the high turbidity and eutrophic conditions of the Yangtze River Estuary and the results provided strong support for its practical application.The main research contents of this topic are as follows:(1)After the previous survey of the basic sea conditions in the Yangtze River estuary,the Shanghai Offshore Marine Environmental Monitoring Network built on the sites of Tangnaoshan Island,Nancaodong,Datuoshan,Jiuduansha,etc.was used as the experimental site for buoy sensor testing.The survey data is collected and analyzed to capture the seasonal variation of oceanic conditions such as temperature,salinity,wind and currents in testing sites.(2)The suitable EVA material was selected for the marine sensor test buoy at the offshore test site,and an EVA tensile experiment was conducted.The test results showed that the hardness and tensile strength of EVA flexible foam materials were in direct ratio to the density;the tensile length was in inverse ratio to the density,and stress-concentrated tears often started from the edges or vertices.The EVA tensile test provided material strength data for the selection of the sensor test buoy,such as a tensile strength of 65kg/m~3 corresponds to a density of 366kpa and a tensile strength of 75kg/m~3 corresponds to a tensile strength of 468.8kpa.(3)Due to the limitation of the lifting device and operating space of small ships,the sensor test buoy is preferably lifted with a single ear when it is launched.A mathematical model of single-ear lifting buoy was built,with a diameter of 1200mm,a height of 650mm,and a total weight of 234.69kg.The force analysis calculated the force transition point x=0.43m and carried out pressure sensor experiments to verify the reliability of the calculation.The tensile strength of the tested buoy was 265.326kpa,which confirmed the reasonableness of the selected 75kg/m~3 EVA material.A universal check calculation method for buoys with a diameter of 3m was formed based on the1.2m buoy force model,and an optimization scheme using 6-screw closed-loop connection was proposed,which provided a systematic guideline for the design and optimization process.(4)A hoisting lifting device was designed and built in the test buoy to observe the biological attachment of the instrument under the high turbidity condition in the Yangtze River Estuary.In the winch voltage test,the testing voltage was 10.8?13.2V,and the rise and fall time was 57.4?73.0s/49.4?56.4s.Since the photovoltaic battery voltage was maintained between 11.8?12.3V,the rise and fall time was uniformly set to 70s/53s.However,,there were problems such as the point switch was eroded by the sea wind,the steel cable holes were abraded,and the wire ropes were worn.An optimization design for screw lifting was proposed.The smooth rod at the top of the screw and the spring device at the bottom were used to eliminate the error of the lifting time due to different voltages.The rise and fall time was set to 90s/85s.The screw lifting strength is much greater than that of the steel cable material,and the disadvantages of the winch lifting can be avoided in the structure,and the reliability of the lifting device is improved.(5)In order to lower economic costs and reduce the difficulty of transportation,delivery and recycling,this research designed a set of anchoring devices that can meet the requirements of selected station and carry out tests.The connection between anchor chain and the bottom support of the buoy used three nylon cables 16mm in diameter and conversion buckles.The anchor chain used a 14mm diameter galvanized anchorless chain.The estimated maximum tension is 23k N,which is far less than the tensile load of 70.76k N and the tensile load is 141.51k N.The anchor is made of cement reinforced concrete,with a volume of 0.152m~3,a density of 2900kg/m~3,and a mass of 440.8kg.The anchoring system can meet the design requirements confirmed by practical experiments.