Accuracy Analysis Of River Microwave Velocity Measurement In Flood Season

As a non-contact flow measurement method with high safety,microwave velocity measurement has been widely used in daily flow measurement.In flood season,the measurement of river velocity needs to face the working scene with much larger flow than usual and a large number of floating objects,which puts forward more stringent measurement conditions and accuracy requirements for the microwave measurement system.Therefore,this paper establishes the water surface fluctuation model and floating object model in flood season.Using the frequency domain electromagnetic simulation method,the influence of model parameters on the accuracy of microwave velocity measurement system is analyzed through simulation calculation.The research contents of this paper include:1.The electromagnetic simulation model of water surface fluctuation in flood season is established.The two models of PM spectrum and JONSWAP spectrum,as well as linear superposition and linear filtering method are analyzed and compared.The PM spectrum and linear filtering method for subsequent simulation are demonstrated and selected.The one-dimensional river water surface fluctuation model with different parameters is established,and the effects of wind speed and sampling points on the wave model are analyzed.2.The scattering coefficient of fluctuating water surface of river in flood season is calculated,and the calculation of river electromagnetic scattering and echo generation process are studied.The method of generating dynamic river echo based on multi scattering point model and quasi-static method is introduced.The calculation process of bistatic scattering coefficient of fluctuating water surface and floating object is introduced based on mom method,including the basic principle of moment method,the selection of incident wave and the calculation of scattering coefficient.The effects of relative dielectric constant,size,position and shape of floating object on bistatic scattering coefficient are studied,The water surface echo signals with and without floating objects are compared.3.The signal processing method and accuracy of microwave velocity measurement are analyzed.The power spectrum estimation method in frequency domain and Burch spectrum estimation method in frequency domain are introduced;The error sources of microwave velocity measurement are studied: the influence of microwave beam width on Doppler frequency shift and the influence of up and down vibration of fluctuating water surface on Doppler frequency shift;Finally,the Doppler shift error is analyzed under the conditions of different wave height,different incident angle,different material,shape,size and floating speed of floating objects.