Hypersonic high frequency (1MHz) fluctuation pressure testing technology and application

High frequency (1MHz) fluctuation pressure acquisition system was developed to study the high frequency fluctuation structures, especially the second mode instability waves, in hypersonic boundary layer in the FD-07 wind tunnel. Wind tunnel ground noises and electromagnetic noises affects measuring of high frequency fluctuation structures. Due to When the qualities of wind tunnel flow field can't change, a series of improvements were made for signal transmission of the system to enhance the ability of anti-electromagnetic interference and anti-attenuation. The improvements contained power supply isolation, shielding cable and ground connection, et al. The experimental results by comparison showed that signal to noise ratio (SNR) of the acquisition system increased remarkably, and the power spectrum densities of noises below 400kHz were reduced by one order of magnitude. Finally, hypersonic boundary stability experiment was performed successfully with the acquisition system in FD-07 tunnel. The second mode wave was detected, and the main frequency extent agreed with the results of linear stability theory (LST).