Method for detecting active sound wave in supersonic flow field
A supersonic flow and sound wave detection technology, which is applied in the direction of measuring ultrasonic/sonic/infrasonic waves, measuring devices, measuring propagation velocity, etc., can solve the problems of limited size of waveguide, inability to apply sound wave signal and its boundary layer response separation, separation difficulties, etc.
Inactive Publication Date: 2008-05-28
INST OF MECHANICS CHINESE ACAD OF SCI
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Also, since in a supersonic wind tunnel the background sound waves and their naturally induced instability waves cover all frequency ranges of interest, even filtering techniques cannot separate the applied sound wave signal and its boundary layer response from the background noise
In addition, what is more serious is that in the wind tunnel experiment, the size of the waveguide and the wind tunnel are limited, and the clutter generated by the back and forth reflection of the sound wave on the waveguide and the wall of the wind tunnel may be different from the original wave. There are signals mixed up, and because the phase between them is generally fixed, it is very difficult to separate
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[0021] Such as figure 1 As shown, the relevant experiments were carried out in a supersonic wind tunnel with a Mach number of 3. To minimize background noise in the wind tunnel, the wind tunnel operates at a very low total airflow pressure, about 0.27 atmospheres. Under this pressure, except for the four corners of the wind tunnel, the boundary layer of the wind tunnel wall is laminar, and the turbulence of the free flow is lower than 0.11%. The supersonic boundary layer is generated by a flat plate placed in the test section 2, and the boundary layer flow is also laminar.
[0022] A series of high-frequency pulse signals are automatically generated by the computer, each pulse includes an appropriate number of oscillation cycles as required, and the frequency is about 8.9KHz. The interval between pulses must be long enough to ensure that various reflected waves have enough time to pass through the measurement point without affecting the acquisition of the next pulse signal; ...
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This invention discloses a hyper sonic flow field active sound wave measurement method, which comprises the following steps: a, generating a series of high frequency impulse signals by computer; b, amplifying the signals through sound frequency amplifier and outputting reproducer driver to generate sound wave impulse; c, conducting the sound wave through wave guide tube to the stable section; d, recording the sound wave and background noise through wind speed meter after the high frequency sound wave enters the wind hole test section; e, separating the background noise from small range of high signals through filter; f, inputting signals to the computer for systematic even computation through amplifier.
Description
technical field [0001] The invention relates to a test method for detecting and analyzing active acoustic wave signals in a supersonic flow field, in particular to a method for detecting the response signal of a boundary layer to an active acoustic wave in a supersonic flow field. Background technique [0002] At present, the reception and amplification of acoustic waves by the boundary layer has been generally considered to be one of the main mechanisms for the origin of flow instabilities. Therefore, it has become an effective means to study flow stability by using external sound waves as interference sources and then studying the response of the boundary layer to sound waves. The response of the boundary layer to acoustic waves generally includes two parts: direct response (Stokes wave) and linear instability wave (Tollmien-Schlichting wave). The Stokes wave and the acoustic interference source have the same phase and similar amplitude, but the amplitude of the linearly ...
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IPC IPC(8): G01H5/00G01H17/00G01M9/02
Inventor 范学军
Owner INST OF MECHANICS CHINESE ACAD OF SCI