Research On The Technology Of Acoustic Detection Of Marine Hydrothermal Vent And Cold Seep

The detection of marine hydrothermal vent and cold seep has been an international researchhotspot in this decade. Bubbling from the nozzle is found to be the common physical characteristicof marine hydrothermal vent and cold seep. This research proposes an ultrasound technique forthedetection of underwater bubble as another means todetect marine hydrothermal and cold seep. Theunderwater bubble is a typical scatterer，which is equivalent into a reflection unit during theresearch process usually. So, the first work of the program involves the studies about specula andscattering of ultrasound with gas bubble in water, which is based on the approach that fromultrasonic single-scattering to multi-scattering. And experiments also include the study of scatteringfrom targets with both rigid and soft water/gas interfaces such as hollow aluminium ball andballoon which contains different gas. The second work is building the acoustic detection system,and developing the theoretical and experimental research about five key ares of technologies:i)underwater target detection, ii) localization and shape recognitions iii) direction of approach, iv)underwater bubble flow detection, v) imaging, which will providefundamental knowledge to assistfuture underwater and ocean exploration research.The layout of this thesis is as follows：Chapter1discusses the background and significance of this research: it reviews the presentdevelopment of domestic and international research in the detection ofmarine hydrothermal and cold seep; outlines the presently underwater ultrasound detectiontechnology and the approach of this research;and to put forward the5key technologies needed formarine hydrothermal vent and cold seep acoustic detection.Chapter2describes the formation mechanism, the physical and chemical properties ofhydrothermal vent and cold seep, and the related underwater acoustic detection mechanism.Itsummarizes the underwater bubble’s acoustic characteristics and scattering properties, and todemonstrate the ultrasound scattering of a soft sphere using MATLAB. This simulation resultprovides the reference for the analysis of experimental data obtain in this study.Chapter3,the design and integration of acoustic detection research system of hydrothermal ventand cold seep is discussed. It describes the design principle of the structure, hardware and softwareof the system. Fundamentals of ultrasonic wave generation, ultrasound sensor, the water tanksystem which consists of a sliding mechanism, and bubble generator have been described. Datarecovery electronics such as the low noise preamplifier, bandpass filter design and realization of data acquisition system based on LabVIEW software platform have been presented.Chapter4,systemcalibration have been presented; the parameters of ultrasonic emissionsignals have been determined; This chapter also describes the experimental scheme of the first3key areas of research for underwater exploration. It presents the main results of ultrasoundscattering from an aluminum block, a hollow aluminum ball, a balloon which contains differentmedium. The results will provide an experimental basis for future study of underwater bubbledetection research.Chapter5,the detection scheme of bubble flow of marine hydrothermal vent and cold seep isproposed. It describes a preliminary experimental concept to analyze the relationship between thephase of ultrasound wave when it encounters gas bubbles in water. This situation is similar to theultrasonic medical imaging technology known as " Phase Contrast Sonic imaging (PCSI)".Chapter6summarizes the full text and gives the prospect of follow-up research work.