The Simulation of Laser Doppler in Velocity measurement of rainwater in pipe

摘要

This study aims to solve the difficulties in measuring the speed of rainwater in pipes. On the basis of the analysis about tracer particles size and number distribution in rainwater pipes and tracer particles velocity distribution, Laser Doppler in Velocity (LDV) was used in this paper to measure the speed of solid impurities within the rainwater pipe, which are regarded as the tracer particles that represent the speed of rainwater. In order to verify the feasibility of the LDV method in measuring the tracer particles in rainwater, a novel mathematic model of LDV, which is based on the theoretic model of fringes and the principle of light interfering and scattering, has been developed to simulate and analyze the relationship among the characteristics of the tracer particles, the velocity of rainwater and the accuracy of the velocity. Analog signals were obtained after simulation. The CHRONUX analysis and time-frequency analysis were used to find the frequency of the analog signals, and then convert the frequency into the speed of the rainwater in pipes. The results show that the method proposed in this study has relatively high accuracy, which is better than other methods of velocimeters. This study indicates that the LDV can apply to the speed measurement of rainwater in practice.