The flow and acoustic characteristics of underwater gas jets from large vertical exhaust nozzles

Abstract

The flow and acoustic characteristics of underwater gas jets exhausted from large vertical nozzles are experimentally investigated in this work with gas flow rates of 30-150 m 3 /h, nozzle widths of d ¼ 10 mm, 20 mm, 30 mm, and 40 mm. A high-speed digital video camera is used to examine bubble behavior and flow regimes. Sound pressure is measured by two hydrophones and recorded by a digital audio tape recorder. The audio and video signals are synchronized to find out the relationship between sound and gas behavior. Experimental results indicate that the general behavior of gas exhausted into water is of periodical necking and expansion. Sound pressure peaks are mostly excited by necking in two ways: pinch-off and redial expansion. Necking itself is a kind of low frequency behavior, corresponding to strong low frequency sounds. Moreover, necking can force the growing bubble to oscillate and emit broadband sound. As the gas velocity increases, necking would happen more frequently, and gas jets would grow into larger volume in shorter time, and then the sound radiated from the gas jets would have higher frequency and larger amplitude.

Unraveling the Contribution of Turbulence and Bubbles to Air‐Water Gas Exchange in Running Waters

“…Third , despite large efforts to reduce background noise in our flume facility, residual noise may have affected the relationship between sound pressure signatures and ɛ and U . For example, the disproportional increase of $${\rho }_{rms,t}$$ relative to ɛ in bubble experiments is likely due to sound created during bubble release from the nozzles of the linear aeration system (Deane & Czerski, 2008; Miao et al., 2018). Fourth , the clear spectral separation between the sounds of surfacing and rising bubbles in our experiment may not always be present under field conditions (Klaus et al., 2019).…”

A Numerical Simulation of the Underwater Supersonic Gas Jet Evolution and Its Induced Noise

“…They found that the turbulence intensity at the air-liquid interface increased considerably with an increase in fluid density, resulting in poorer jet stability. Regarding the noise characteristics of underwater gas jets, the noise from low-speed jets is primarily caused by bubbles [18][19][20][21][22]. However, based on the research conducted by Liu et al [23], who used a large eddy simulation (LES) to analyze the flow structure and noise radiation of underwater supersonic jets, the noise generated by high-speed jets originated primarily from the shockwave structure of the jet.…”

A machine learning approach for underwater gas leakage detection

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