| The measurement of water flow velocity has very important application value in the fields of hydrological monitoring,fishery production,marine traffic safety,etc.In order to meet the needs of non-uniform flow velocity measurement and more precise flow velocity distribution characteristics measurement,this paper focuses on the research of high-resolution acoustic multi-beam forming and fine layered multi-beam radial velocity measurement technology to achieve high-resolution,wide-coverage flow measurement in complex water flow environments.The specific work is as follows:(1)The limitation of traditional acoustic doppler current profile(ADCP),in the measurement of complex non-uniform flow field is analyzed,and a water flow field measurement method based on acoustic multi-beam technology is proposed.Considering that the received signal is the superposition of scatterer echoes in the entire water body,a multi-beam layered radial velocity estimation method is given for the problem of velocity estimation in different regions of the water body.Meanwhile,in order to solve the problem of insufficient spatial opening angle range of the transducer under the condition of high-frequency signals,the array is designed as an arc array to achieve a wide spatial opening angle,and the array structure simulation and spatial directivity analysis are carried out.(2)Aiming at the limitation of conventional beamforming in multi-beam current measurement,a water flow field measurement method based on distance and azimuth two-dimensional beamforming is proposed.At the same time,receiving the side lobes in the flow field measurement will have an impact on the frequency offset estimation of the flow measuring unit.For this problem,the Chebyshev weighting method is used to suppress the side lobe interference.Finally,the simulated multi-beam water flow reflected acoustic signal was used to verify the validity and feasibility of the multi-beam radial velocity measurement method.(3)In multi-beam measurement,there is the problem of inconsistent spatial resolution of the measurement unit in the water body.An equal beam footprint measurement method and a refined layering method with varying overlap rates are proposed.At the same time,in view of the measurement problem caused by the inconsistency between the artificial stratification method and the actual fluid for the continuous flow layer,an interlayer interference suppression method based on moving average is proposed,and the effectiveness of the method is verified by simulation.(4)Aiming at the characteristics of multi-beam radial velocity measurement module with large calculation amount and algorithm logic reusable,a multi-core parallel software implementation method is given.Meanwhile,joint debugging and pool test are carried out on the completed multi-beam flow measurement test system.The test results show that the flow measurement method proposed in this paper can meet the needs of water velocity measurement. |
