Vortex whistle as a flow meter

A vortex whistle consists of three elements (1) an inlet, (2) a cylindrical cavity and (3) a cylindrical down stream tube. The inlet is tangentially connected to the cylindrical cavity and the cylindrical down stream tube is connected to the center of the cavity top. Air blown into the tangential inlet revolves around the cylindrical cavity and whirls out from the down stream tube. The whistle sound is thus generated. The frequency of the sound is controlled by the amount of air. This fact suggests that the vortex whistle can be a frequency dependent flow meter. A mathematical model that describes how the vortex whistle generates the sound is presented to give a theoretical foundation of the flow meter. The validity of the model was examined by experiments. How the structure of the whistle influences the performance is investigated by on analysis of the model and the experiments. Conditions that yield both a wider range and a smaller pressure drop were investigated. Further the microphone site which yielded the highest S/N ratio for the was found. The vortex whistle that satisfies the above conditions has the characteristics of simple structure, good linearity, a wide range-ability and the frequency of the sound is easily signal-processed