Abstract
Experimental investigations were performed on the generation of resonant sound by flow in a pipeline containing two closely spaced orifice plates. The frequencies of the generated tone were scrutinized as the velocity was increased from 3 to 25 m/s. To determine the convection velocity of the vortices formed between two plates, measurements were made of the phase angle of the fluctuating velocity using a hot-wire anemometer. The vortex shedding frequency is locked into the pipe modes, but indicates a slight increase with an increase in the flow velocity. The ratio of the distance between the two orifice plates to the spacing of vortices is expressed by m+ε, where m is an integer and ε is a decimal part. It was found that the value of ε decreases with increasing flow velocity within a range from 0 to 0.5, and a change of the number of vortices or a frequency jump occurs when ε reaches a critical value.
