Study Of Measurement Method For Seafloor Hydrothermal Vent Flow Field Based On Optical Image Sequence

The21st century is the century of the ocean, and the vast ocean is rich invarieties of resources. The seafloor hydrothermal region has become an importantaspect of oceanographic survey and research in countries around the world because ofits potential mineral and biological resources. Seafloor hydrothermal vent dischargethe thermal fluid of magma mixed with seawater of deep sea flowing through thespecial structure of the chimney constantly, and it generates the complex heat andchemical fluxes process between lithosphere and seawater which involves a numberof scientific issues, such as the heat and material fluxes from hydrothermal vent,hydrothermal mineralization environment and mineralization rate, the impact of tidal,tectonics, magma, seismic and other geological effects imposed on the hydrothermalsystem, as well as the hydrothermal ecosystem in hydrothermal region. As one of themost basic characteristics of seafloor hydrothermal system, the amount of energyflows through them. Thus, the observation of hydrothermal flow is the most importantand basic parameter for other studies comprehensively and deeply.Because of the special structure of the seafloor hydrothermal chimneys, extremehigh temperature and highly corrosive of fluid, it is difficulty to obtain long timeseries of in situ velocity data by conventional observation methods. In this thesis, amethod of hydrothermal fluid flow rate measurement based on the non-contactmonitoring technology is investigated. The goal of this work is to explore the imagevelocimetry technology for in situ fluid monitoring and analysis of hydrothermalvents with high spatial resolution, and to improve our understanding of seafloorhydrothermal flow velocity characteristics in China. In the first half of the paper,hydrothermal eruption simulator was constructed according to the hydrothermalgenerating mechanism and the nature of the fluid dynamics, and non-contact highspatial resolution observation system based on optical imaging is implemented.Around the modern seafloor hydrothermal environment, graphite particle and blackcarbon (ink) are chosen to simulate hydrothermal fluid, a prototype of hydrothermalanalog measurement system is constructed. In the latter part, image sequences of thesimulation hydrothermal flow is obtained experimentally, and the calibration methods of optical imaging system for velocity of flow and flow field are established. Theanalysis results shows that matching method based on gray has better performanceover others for velocity of flow field analysis. Finally, ocean seafloor hydrothermalvideo image taken by ROV is used to verify matching method based on gray. Theresult shows that the proposed method has the potential value for real-worldapplication.