Study On The Device Of Acoustic Temperature Measurement For The Seafloor Hydrothermal Vents

Temperature fields measurement around seafloor hydrothermal vents becomes animportant part of marine science research such as investigation of the heat flux ofhydrotherm, monitoring of marine environment, creation of the ocean circumfluencemodel, forming of hydrothermal mineralization, activities of hydrothermal biosphere,etc. It also provides an important basis for investigating the character of hydrothermalfluid and its chemical components convection-diffusion in seawater, as well as theformation of hydrothermal sulfide chimneys.However, owing to extreme submarine hydrothermal vents environment of hightemperature, high corrosion and low visibility, there's no effective non-contact way tomeasure the temperature fields of hydrothermal vents. Yet for this reason, it is a verymeaningful thing to manufacture an accurate acoustic in-situ measurement device formeasuring the temperature fields around seafloor hydrothermal vents.The thesis consists of 6 chapters based on acoustic temperature measurementmethods and systems for seafloor hydrothermal vents as follows:Chapter 1 discusses the background and significance of the research,summarizing the temperature measurement around seafloor hydrothermal vents,acoustic temperature measurement, current staus and development trend ofhydrothermal vents temperature measurement domestically and internationally. Then,the mainly task and content in this study are proposed.Chapter 2 introduces the basic principles of acoustic temperature measurement.In order to give a basis for choosing the model of temperature field simulation,researching the best ratio of hydrothermal region and cold region, setting up thereconstruction mesh, designing the acoustic transducer rack, building the artificialmodel of temperature field in a pool and laying the device of acoustic temperaturemeasurement at the sea trial time, and conducting the numerical simulation around asubmarine hydrothermal vent.In chapter 3, first we propose a high resolution multipath time-delay estimationmethod by means of interpolation algorithm. Next, the propagation path of sonicwaves in 2-D fields of non-uniform temperature around hydrothermal vents isnumerically calculated using Fermat's theory and by variational calculation,which helps compensate from flexual lines to straight lines and reconstruct temperature fieldsimultaneously with better reconstruction accuracy. Then, we have made a scrutinyinto the model of temperature field simulation, which based on the total least squares.And an error analysis is performed after the reconstruction temperature field.In chapter 4, a new acoustic measurement system of temperature distributionaround seafloor hydrothermal vents has been developed. Regarding the numericalsimulation of actual working conditions of submarine hydrothermal vents and thesimulation of model temperature field, the final design and integration of majorhardware and software system are performed.In chapter 5, the laboratory experiments, and lake trial in Lake Qiezishan,located in Longling Country, Yunnan Province, China, have been carried out. Herewe study the integrated performance of the acoustic measurement system oftemperature distribution around seafloor hydrothermal vents. In the experiment parts,we discuss the procedure, method, results and the detailed analysis of theexperimental results.Chapter 6 summarizes the full text and gives the prospect of follow-up researchwork.