Low turbulence intensity and spectrum measurement research in aeroacoustic wind tunnel

The 5.5m×4m low turbulence aeroacoustic wind tunnel is a low speed single-re-turn wind tunnel,capable of performing aeroacoustic,low turbulence and general low speed tests.The flow of this tunnel presents the important quality of low turbulence intensity,which needs to be measured accurately.The band pass filter and signal noise separation are the two main methods to process the low turbulence intensity data.However,the parameters of the two methods are different,and thus there is no direct comparison between their results.In this paper the low turbulence intensity of the flow field is measured in the closed test section of the 5.5m× 4m low turbulence aeroacoustic wind tunnel with the hot wire anemometry.A 0.5Hz high pass inertia attenuation filter is adopted to process the data according to the noise analysis,and the re-sults are compared with other two methods,that the 0.5Hz~5kHz band pass filter and the sig-nal noise separation.Noises in the flow field fluctuation are analyzed based on the power spec-trum and the Strouhal numbers.The electromagnetic noise and support disturbing noise are found in spectrum domain of 40Hz~10kHz.Using a 0.5Hz high pass inertia attenuation filter, the flow field turbulence intensity is measured and found to be less than 0.05% at the speed of 30~100m/s.Experimental results show that,the high pass inertia attenuation filter method can be used to control the disturbance to the results induced by noises,which is a practical method for processing the low turbulence intensity digital signal.