Experimental study on the use of a vortex whistle as a flowmeter

A vortex whistle has a simple structure, good linearity in the relationship between flow and sound frequency, and a wide range in that frequency. This paper suggests that the vortex whistle can be used as a frequency-detecting flowmeter. First, we investigated characteristics of the vortex whistle. We describe a pressure loss model that was built from experimental results. Visualization experiments carried out by using a very high speed camera showed that vortices coming from the outlet of the whistle included flow components whose flow line changed in synchronization with the frequency of the vortex whistle sound. From these results, we confirmed the existence of precession motion of flow around the outlet area. Further, from numerical analysis of the inside of the vortex whistle, we discovered that the sound signal with the best signal-to-noise ratio (SNR) was detected when the microphone was set parallel to the wall of this outlet of the whistle. Furthermore, we researched the temperature characteristic of the vortex whistle sound.