Flow Monitoring Research Of River Based On High Frequency Acoustic Propagation

Acoustic applications has been extended to many fields and especially is of great significance for data communication,mineral exploration,energy development,hydrological monitoring in underwater environment.Underwater environment is complex and changeable.Sound waves is affected by many factors in the process of transmission.We can investigate the medium parameters by analyzing transmission performance of sound waves.Therefore,the measurement of sound waves transmission path,transmission time,transmission loss,the distributions of sound energy in underwater medium is significant.Many ways could be used to present the environment surveillance on rivers.In this study,attention will be paid to monitoring temperature,current and flow in rivers.First,we accessed relevant information of hydrologic monitoring of rivers to determine the inversion method of temperature and current,which was based on acoustic detection technology.We improved the basic tomography theory and instrument in our research by applying high frequency acoustic tomography technology in river hydrologic monitoring.Measurement experiments were carried out in the Jiulong River,in which two sound stations have been established on both river banks.The water level,temperature and terrain have also been measured for further analysis.Considering the actual conditions of experiment field and available infrastructures,we encoded the sound signal with Pseudo-noise sequence and Chaos sequence to improve signal-to-noise ratio and anti-multipath ability.We analyzed the sound ray propagation paths under the river’s terrain through bellhop,a simulation acoustic tool.A high frequency(60 kHz)acoustic tomography system which consists of industrial personal computer,acoustic transducer and other signal processing module has been developed,This system can transmit and receive sound signal in real-time.The results of temperature and current data will be uploaded and released on the server.There were typhoon and rainstorm days in Jiulong River valley during the experiment.The change of flow and temperature was monitored by our system.The results showed that the measurement was well correlated with the ADCP data,and the high frequency acoustic tomography system was reliable for flow measurement.