The Calibration Method Of The Starting Threshold Of Wind Velocity And The Design Of The Experimental Box For The Cup Anemometer

Among the various wind speed measuring instruments, cup anemometer is used widely. But when the cup anemometer is used outside for a long time and affected by various weather factors, which leads the cup anemometer aging and the starting wind speed increases, It is necessary to calibrate the cup anemometer at this moment. But now we usually send the cup anemometer to the professional wind tunnel laboratory for the calibration of cup anemometer. This way is time consuming and laborious, which can not meet the demand that calibrating the anemometer in the field. Therefore, it is necessary to take a new approach to calibrate the starting threshold of wind velocity of cup anemometer.In order to solve the problem of real-time calibration of the starting threshold of wind velocity of cup anemometer, this paper analyzed the factors of the starting threshold of wind velocity. And the formula of starting threshold of wind velocity is derived. The wind pressure coefficient in the formula is fitted. A new method for measuring the starting threshold of wind velocity is put forward on the basis of wind pressure coefficient. Based on this method, the experimental box for the starting threshold of wind velocity calibration is designed. The design of the experimental box for the starting threshold of wind velocity calibration mainly includes two parts.The first is the experiment box structure design. The second is the hardware circuit design of the experimental box.The structure design of the experiment box is the key part of this paper. Before the structure design of the experimental box using the finite element analysis method, the basic theory of computational fluid dynamics is studied. The main contents include that three basic governing equations, the discussion on commonly used turbulence models, description of the simulation analysis of the reasons for the selection of Spalart-Allmaras turbulence model, simulation parameters of turbulence model are determined. The grid division has a key role in CFD simulation, which shows that the reasons for the selection of unstructured grid. The working process of CFD is discussed in detail, and the specific process of the simulation experiment is confirmed.In the experimental box structure design, a large number of experimental box structure models are established by the 3D CAD software. The suitable turbulence model, the calculation model and the simulation parameters are selected. The finite element analysis software FLUENT is used to simulate the numerical simulation, and the results are visualized, the flow field characteristics of experimental box are studied, which influenced by different structures of power section, rectifying section and contraction section. The flow field characteristics of the final experimental box were studied at different fan speeds and the flow field of the whole experiment box was also investigated.The hardware circuit design of the experimental box mainly includes that PWM waves control the DC motor in the fan power section, the photoelectric switch circuit for detecting whether or not the wind speed meter is started and measurement of wind speed based on the closed-loop constant temperature with the hot-line.Summarizing the design of the calibration experimental box, the hardware circuit of experimental box function has function integrity. The simulation results show that the flow field in the exit section of the experimental box could meet the calibration requirements, which can achieve the purpose of field calibration.