Experimental study of the jet-driven Helmholtz oscillator

Abstract

Experimental studies of the model of the jet-driven Helmholtz oscillator, which is an axisymmetric channel of variable cross section, have been carried out. The model consisted of a cylindrical resonator chamber closed on the sides by two covers. The oscillator was excited by a stream of air flowing through the chamber between the inlet and outlet holes made in the side covers. The influence of the geometric dimensions of the chamber and the openings in the covers on the amplitude of pressure fluctuations was studied, and the optimal configuration of the channel was determined. Particular attention is paid to the study of the influence on the amplitude of pressure fluctuations of the shape and size of the nozzle - the hole in the front cover. The pressure drop across the nozzle, to calculate the speed of the jet at the entrance to the chamber, and the parameters of pressure fluctuations in the chamber, to plot the frequency response, were measured. Observations of the appearance of a jet-tone and the excitation of acoustic modes at the frequency of natural oscillations of the chamber-resonator with a smooth increase in the jet velocity were made. The absence of a relationship between the frequency of the jet-tone and the resonance frequency in the chamber was noted. Recommendations for the design of a jet-driven Helmholtz oscillator intended for use as a borehole transducer for stimulating an oil reservoir are presented.