Study On Ocean Microstructure Measurement Technology Platform Based On Underwater Glider

As an important ocean phenomenon and the carrier of substances for mixing,diffusion and energy transfer,the ocean microstructure turbulence has a significant effect on the marine environment,including temperature and salinity characteristics,movement of seawater and distribution of granular and dissolved substances.Turbulence observation is a hot topic in the field of marine observation technology.It is the key in the turbulence research that how to measure the microstructure turbulence and get the dissipation rate of turbulence kinetic energy.However,the vertical microstructure profiler,a kind of conventional marine observation platform,must be deployed and recovered in a fixed location when measuring the microstructure turbulence,thus is time-consuming,labor-intensive,and with low efficiency and high cost.On the contrary,as a new generation of mobile autonomous observation platform,the underwater glider has the advantages of long endurance,large range and being free from the influence of ship time and sea condition,making it possible to achieve long-term and continuous turbulence observations with high-efficiency and low consumption.Therefore,this paper proposes that the underwater glider can act as a carrying platform where a turbulence observation instrument is integrated,thus constructing an ocean microstructure turbulence observation platform to achieve long-term and continuous observation of turbulence.The work presented in this paper focuses on the integration of the underwater glider with the turbulence observation instrument.Firstly,the requirements of turbulence observation for the velocity and attitude of the glider are analyzed based on the measuring principle of turbulence observation instrument.Then,a kinematic model in the vertical plane is established to analyze the performance of the glider and obtain the motion parameters satisfying the turbulence measurement requirements.Secondly,the vibration characteristics of the glider are studied in time domain and frequency domain by using the Fourier analysis method.Improvement measures are proposed in order to reduce the adverse effects of the vibration noise on the measurement.Besides,the Goodman technique is used to separate vibration signal to achieve higher measurement precision in the data processing.Finally,a new method of calculating dissipation rate of turbulence kinetic energy is proposed based on fast response thermistors.Maximum likelihood estimation(MLE)is used to fit temperature gradient spectrum to Batchelor spectrum,the correctness of which is evaluated by comparing the dissipation rate of turbulence kinetic energy from shear probes and fast response thermistors.The integration of the turbulence observation instrument and the underwater glider is realized based on above achievements.Included in the experiment were tank test and sea trail.The results of the experiment indicate that each performance index of the observation platform has reached the design requirements,which can meet the standard of ocean turbulence observation.