PURPOSE: To measure the fluid speed and the particle speed in the vicinity of the opened port part of a resonance tube with high precision by detecting the max. value of the fluid speed, in time sequence, in the vicinity of the opened port part of a λ/4 resonance tube equipped with a sound source oscillator having a wave length of λ and a fluid feeding port at one edge and equipped with the opened port at the other edge.
CONSTITUTION: A speed measuring device is constituted of a λ/4 resonance tube 3 which is equipped with a fluid port for sucking air from a working air tube 1 and a sound source 2 at the left edge and is opened at the right edge. When the sound source 2 is oscillated with the frequency having a wave length λ by an oscillator 4, the sound wave generated by the sound source 2 becomes the stationary wave in the resonance tube 3. When the flow speed of the fluid at the position of a heating wire HW installed at the opened port of the resonance tube 3 is measured by a constant temperature type heating wire flow speed meter 5, the measured value is represented in time sequence, and the max. value in the high level range and the peak in the low level range appear alternately. The max. value of the fluid speed in the vicinity of the opened port of the resonance tube 3 is detected in time sequence, and a plurality of max. values are discriminated to the values in the high level range and in the low level range, and the fluid speed and the fluid particle speed at the opened port are calculated from the max. value.
NARITA AKIRA
NAMIKATA HIROYUKI
ADACHI KOUJI
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