Studies On Simulation Of Gust Spectrum In The Wind Tunnel

The main purpose of this study is to simulation a random fluctuation of wind velocity fitted to specified power spectrum in low frequency range in our wind tunnel.Parameter method was adopted to generate time series conforming to the specified power spectrum. A autoregressive model was estimated by program which based upon Yule-Walker equation. Good agreement was obtained between the simulated spectrum and the target spectrum.This paper describes the procedure of generating the gust in the wind tunnel. The fan was controlled by PC through the serial communication between PC and transducer. The random control signals was generated by MATLAB programs and then was send into the control software by using DDE (dynamic data exchange). So the control platform was established by the two software.Dynamic characteristic of the fan system was tested in this paper. The time constants of acceleration and deceleration was gotten and Bode diagram of frequency response was presented. The results show that the frequency response of the system is satisfying in the range up to 0.2 Hz.Four white noises which have different cut off frequency were used as random control signal(target signal) in the simulation experiment. The results indicated that the correlation between the measured velocities and target signals decreased when the cut off frequency of the target signal increased. The correlation between the measured velocities and the target signals with cut off frequency of 0.1 Hz was 0.85~0.9. But it was only about 0.3 when the cut off frequency of target signals increased to 0.4 Hz. The coherence functions between the measured velocities and target signals showed high values(above 0.5) in the frequency range up to 0.1 Hz.In another simulation experiment the time series simulated by program conforming Simiu spectrum was used as target signals. The results showed high correlation between the measured velocities and the target signals.