The Characteristics of Self-Resonating Jet Issuing from the Helmholtz Nozzle Combined with a Venturi Tube Structure

Abstract

Self-resonating waterjet is a new type of waterjet technology that has been widely used for many practical applications. In order to further improve the performance of self-resonating waterjet, the Helmholtz nozzle was improved by replacing the upper part of a traditional contract structure with a venture tube one. This composite nozzle of a venturi tube structure and a Helmholtz resonator was proposed based on the working mechanism of self-resonating waterjet nozzles and the instability of cavitation flow in venturi tubes. Furthermore, the results were also compared with those generated by a conventional Helmholtz nozzle under the same conditions. The frequency of the pressure pulsation in the oscillating cavity and at the outlet was obtained and analyzed by the classical Fast Fourier transform (FFT) method. The results showed that the main frequency of the pressure oscillation rises to 2362.78Hz, and the peak and average values of the pressure are increased by 45% and 12.5% respectively at the outlet of the composite nozzle. In the oscillating cavity of composite nozzle, the pressure oscillations in the central region have higher frequencies and amplitudes, while near the wall are reversed.

Flow Field Characteristics and Flotation Efficacy in a Pulse Jet Flotation Machine: A Comprehensive Investigation

“…point in the PJFM. The Fourier spectrum displays sharp peaks at the same frequency, indicating better pulse characteristics [13]. The pressure pulsation amplitude at the outlet of the upper nozzle is approximately 90.…”

“…The self-oscillating jet is a new type of jet developed in recent years that can produce strong self-excited oscillations without an additional external driving mechanism. Its pressure field, velocity field, and density field all pulsate strongly with time, and there is a complex coherent interaction between these physical fields [11][12][13]. The self-oscillating jet produces oscillation in the special fluid structure through self-excitation, modulating the continuous jet into an oscillating pulse jet, thus making full use of the water hammer effect and aggregation effect of the high-frequency impact of the liquid beads and avoiding the water cushion effect of the continuous jet impact.…”

Characteristics of Oscillation in Cavity of Helmholtz Nozzle Generating Self-excited Pulsed Waterjet

“…Combined with theoretical calculation and experimental results [29][30][31], four nozzles with different inner diameters were employed in the experiment, and the specifications of the nozzle are shown in Table 1. The pressure signals were received by the data logger (model: HBM Quantum X MX840B-8) at a 19200 Hz sample rate.…”

Numerical Study on Flow-Induced Noise of Deflector Jet Servo Valve Based on LES/Lighthill Hybrid Method

“…erewith, the generation, growth, motion, and collapse of these large-scale vortices will lead to a strong pulsating pressure acting on the jet periodically. Coupled with the jet instability and interactions of the jet and the environmental fluid, the selfexcited oscillation jet will be formed, and the oscillation phenomenon will form a closed loop in the oscillation cavity [34][35][36].…”