Research On Current Detection Method Based On Multi-Beam Technology

The use of acoustic methods to detect the characteristics of ship wakes is gaining more and more attention,and has important theoretical significance and application value.In view of the fixed beam angle of the current widely used Acoustic Doppler Current Profiler,it is necessary to use external machinery to change the weakness of the measurement area.The Doppler current measurement algorithm is combined with the multi-beam technology with wide coverage and multi-angle characteristics.The acoustic characteristics of wake bubbles are studied from the aspects of wake scattering intensity and flow velocity estimation.On the basis of consulting a large number of documents,it is investigated and reviewed that the domestic and foreign research status of multi-beam technology,wake acoustic detection technology and Doppler current measurement technology.The current Doppler current measurement methods are analyzed,and the current method of detecting the bubble characteristics of the ship's wake using acoustic methods is studied.Based on the multi-beam phase control technology,the transducer array and its directivity are studied,and the correctness of the theoretical derivation is verified by computer simulation.Refer to the relevant information,the volume scattering intensity measurement calculation method is derived according to the beamforming algorithm and sonar equation.Based on the traditional current measurement method,multi-beam technology is introduced,and the multibeam radial flow velocity measurement method and current velocity conversion method based on complex autocorrelation frequency estimation are given to provide theoretical support for designing the prototype.The multi-channel phase-controlled signal source and control software of the multi-beam current measurement transmission system are designed,and the performance test of the system is carried out,which meets the requirements of various indicators of the multibeam current measurement system.In order to verify the bubble detection method based on the multi-beam system,a multibeam experimental platform is built.Wake bubbles are simulated in noise-suppressing pools.It is obtained that the spatial distribution,scattering characteristics,Doppler distribution of bubbles and spatial and temporal characteristics of bubbles with propeller rotation from the aspects of scattering intensity and Doppler frequency shift.The experimental results prove the effectiveness of the acoustic multi-beam system to detect the spatial and temporal characteristics of the bubble wake field.