Research On Flow Velocity Measurement Technology Based On Laser Doppler Technology

With the progress of industrialization in the world and the development of China's modernization,the continuous construction and development of water conservancy projects,a large number of water conservancy projects need to detect the speed of water flow.It includes many scenes,such as water diversion channel,offshore oil well,river embankment and dam.In the scene of turbulent water flow,the erosion of water flow is often unfavorable to some facilities in the project.Therefore,it is necessary to study the degree of erosion of bridges and other facilities caused by turbulence with sediment in levees,dams and diversion channels,or to study the state of geothermal water gushing in the ocean due to volcanic activity or earth plate movement.At the same time,the detection method of flow velocity is also developing.The traditional way to detect the velocity of fluid is based on ultrasonic Doppler effect.This way needs to contact fluid measurement,which has low spatial resolution,easy to be electromagnetic interference and low measurement accuracy.The velocity sensor based on laser Doppler velocity measurement technology is superior to the traditional acoustic velocity sensor in the above aspects,and it is very suitable for fluid velocity detection in harsh environment.Therefore,the study of laser Doppler velocimetry technology is the key to realize the safety of water conservancy facilities and the environmental assessment of Marine Geothermal water,which has important engineering value.Using laser Doppler technology to measure the flow velocity can obtain the flow velocity more efficiently and accurately.Laser Doppler velocimetry model is an important way to monitor the flow velocity in many water conservancy projects.Based on the principle of laser Doppler velocimetry,this paper studies the detection of fluid velocity and ocean current velocity in the flume,and designs and realizes the laser Doppler flow velocity sensor and the ocean current velocity monitoring system connecting the land and sea.The main research contents and achievements are as follows:1.the reference light enhanced velocity measurement model based on the optical circulator is designed.The model of the speed measurement system between sea and land is designed.The optimized optical path is designed for the reference optical speed measurement model.2.the Doppler signal receiving scheme and signal processing method based on optical heterodyne detection technology are studied and designed.The fast Fourier transform processing algorithm is designed and implemented.The measurement scheme design for measuring the velocity of solid motion,flume fluid velocity and ocean current velocity is completed respectively.3.the system of measuring the velocity of solid motion,flume fluid and ocean current is completed.