Research On Detection And Quantification Technology Of Leakage Gas Based On Multi-Beam Bathymetry Sonar

Driven by the demand for national marine oil and gas development safety and acoustic monitoring of seabed carbon storage,research on the detection and quantitative estimation of underwater leakage gas has become increasingly in-depth.This article focuses on the domestic and foreign development trends of active acoustic survey research on underwater leakage gas.Through a combination of theory and practice,the article carries out relevant basic theoretical and applied technical research,while constructing an experimental platform to conduct experimental research.With the support of national science and technology major projects and key projects of the National Natural Science Foundation,the article conducts in-depth research on three aspects of leakage gas detection,velocity estimation,and flux estimation based on multibeam bathymetry sonar.Firstly,research is conducted on leakage gas target detection technology based on multibeam bathymetry sonar,focusing on one-dimensional beam data and two-dimensional image data.On the one hand,to address the problem of missed detection of water targets in one-dimensional beam data,a multi-echo detection algorithm based on Variable Index-Constant False Alarm Rate(VI-CFAR)is proposed,which ensures the detection of water targets while maintaining bottom detection.The effectiveness of the method is verified through measured data.On the other hand,a dynamic inter-frame two-dimensional Cell Averaging-Constant False Alarm Rate(CA-CFAR)detection method is proposed,combined with a morphology classifier,to complete the detection of leakage gas in three-dimensional space.The external field experiment shows that the proposed method can effectively detect and separate leakage gas,providing technical support for the research of leakage gas quantification estimation methods.Secondly,the research focuses on the leakage gas velocity estimation method based on multibeam bathymetry sonar.Firstly,the sonar imaging and preprocessing method for leakage gas is established,and the imaging effect of water targets is improved by wavelet denoising and dynamic brightness allocation.Secondly,considering the limited applicability of optical equipment underwater and the difficulty in measuring the rising velocity of leakage gas,a leakage gas velocity estimation method based on Farneback optical flow is proposed to accurately estimate the flow field velocity.Furthermore,to address issues such as low sonar image resolution and the susceptibility of water target feature points to noise,a Multi-beam Sonar-Scale Invariant Feature Transform(MBS-SIFT)local feature extraction method with good stability is proposed.And then,a leakage gas velocity estimation method based on MBS-SIFT feature flow is proposed to improve the accuracy of leakage gas velocity estimation.Finally,the effectiveness of the proposed methods is verified through experiments in water pools and lakes,laying a foundation for leakage gas flux estimation.Thirdly,we study the flux estimation method of leakage gas based on multibeam bathymetry sonar.Firstly,considering the sparsity and internal information contained in the point cloud data,traditional surface digitization methods are not applicable.We propose a method to construct a three-dimensional point cloud data by stitching together a sequence of water column images,and reconstruct the contour of the leakage gas using the Alpha Shape algorithm.Secondly,we improve and deduce the theory of high-frequency acoustic wave bubble backscatter respiratory mode,and combine it with Anderson mode series solution and Stanton high-pass approximation solution to achieve fast and accurate calculation.Thirdly,based on the measured data of the volume scattering intensity of the multibeam bathymetry sonar bubble group,we establish a model for estimating the flux of the leakage gas,and estimate the size distribution of the leakage gas through adaptive parameter estimation,thus calculating the volume and flux of the leakage.Finally,we conduct a quantitative assessment of the leakage gas in the South China Sea using multibeam bathymetry sonar mounted on an Autonomous Underwater Vehicle.The results show that the proposed method can accurately estimate the rising velocity and flux of the leakage gas,thereby improving the quantitative estimation function of multibeam bathymetry sonar for leakage gas.In conclusion,based on image processing and acoustic theory,and supported by the technology of leakage gas target detection,this paper has developed methods for estimating the speed and flux of leakage gas using multibeam bathymetry sonar.Through the application of techniques such as MBS-SIFT feature flow,and gas flux estimation method,the detection and quantitative estimation of underwater leakage gas have been achieved.