The Adaptive Design And Sea Trial Application Of Underwater Glider For Current Observation

As an important parameter of ocean dynamic environment,the ocean currents play an important role in global climate change,coastal erosion and marine organism migration,etc.Autonomous underwater gliders with the advantages of low power consumption and low operation cost can meet the needs of long endurance,large range and spatial ocean environment detection.By integrating the miniaturized and low-power sensors,gliders can obtain the high-resolution,wide-coverage and multi-parameter flow field data,and show a broad prospect of application.This dissertation presents currents observation and sea-trial research for the Petrel-?glider developed by Tianjin University.The main contributions are summarized as follows:1.Based on the Newton-Euler equation,the dynamic model of glider under the buoyancy variationis established considering the practical working environment.The dynamic characteristics under the loss of buoyancy are considered in this model.The ideal installation position of electromagnetic velocity sensor in the glider is studied with the method of computational fluid dynamics.On this basis,the sea trial of glider integrated with electromagnetic velocity sensor is carried out.Combining the sea trial data and dynamic model,the angle of attack and hydrodynamic coefficients are optimized.The accuracy of the hydrodynamic coefficients obtained by the method is verified by comparing the results of dynamic simulation and experimental results.2.By integrating a quasi-static flight model and the observed glider vertical velocity from pressure,vertical water velocities are estimated.The influence of structural parameters and hydrodynamic coefficient fluctuations on vertical velocities is discussed by method of local sensitivity analysis.Those parameters with high sensitivity are optimized by constructing an objective function.Based on above theory and the optimized coefficients,the vertical water velocities are estimated with accuracy of?4mm/s.The cooperative observation test with multiple gliders is carried out in the northern South China Sea.Combined with the thermohaline structure obtained synchronously by gliders,the spatial distribution of internal waves in the survey area is yielded.3.In order to keep the glider's real pitch around the ideal observed pitch of AD2CP(±17.4~°)for minimizing the measurement error,the wing position is optimized and re-placed considering the economy and stability of glider flight simultaneously.The errors of AD2CP measurement data are analyzed and corresponding quality control procedures are performed to screen on high-quality measured data.Based on the inverse method and combined with motion characteristics of glider,the absolute horizontal water velocities are estimated.A conservative mathematical error model is used to estimate the processed current uncertainties in the inversion method.The statistical error analysis shows that the error in the eastward or northward averaged velocity is less than 0.04±0.025 m/s.4.Considering the randomness of the internal solitary waves and based on the analysis of their spatial and temporal distributionin the South China Sea,the Petrel-?glider conducted internal solitary wave observations in the northern South China Sea in August 2017.Combined with the analysis of a moderate-resolution imaging spectroradiometer true-color image,it is verified that the thermohaline fluctuation is caused by the passage of internal solitary waves.The difference between observations by the gliders and moorings is compared,and a method of the vertical water velocities estimated from gliders used to identify the parameters and types of captured internal solitary waves is researched.