Numerical analysis of flow induced noise propagation in supercavitating vehicles at subsonic speeds

Abstract

Flow supercavitation begins when fluid is accelerated over a sharp edge, usually at the nose of an underwater vehicle, where phase change occurs and causes low density gaseous cavity to gradually envelop the whole object (supercavity) and thereby enabling higher speeds of underwater vehicles. The process of supercavity inception/development by means of "natural cavitation" and its sustainment through ventilated cavitation result in turbulence and fluctuations at the water-vapor interface that manifest themselves as major sources of hydrodynamic noise. Therefore in the present context, three main sources are investigated, namely, (1) flow generated noise due to turbulent pressure fluctuations around the supercavity, (2) small scale pressure fluctuations at the vapor-water interface, and (3) pressure fluctuations due to direct impingement of ventilated gas-jets on the supercavity wall. An understanding of their relative contributions toward self-noise is very crucial for the efficient operation of high frequency acoustic sensors that facilitate the vehicle's guidance system. Qualitative comparisons of acoustic pressure distribution resulting from aforementioned sound sources are presented by employing a recently developed boundary integral method. By using flow data from a specially developed unsteady computational fluid dynamics solver for simulating supercavitating flows, the boundary-element method based acoustic solver was developed for computing flow generated sound.

A Numerical Investigation of Supercavitation Vehicle’s Hydrodynamic Noise

“…Nevertheless, through the occurrence of cavitation, the cavitation bubble cluster becomes the main source of hydrodynamic noise. In natural cavitation conditions, the collapse of cavitation bubbles and pressure fluctuations at the gas-liquid interface generate substantial noise, and under ventilation conditions, the jet from vent to supercavitation structures also generates noticeable noise [14][15][16]. The complex mechanism of cavitation bubble cluster collapse and its pressure wave propagation makes it difficult to establish a supercavitation noise model [17,18].…”

“…Nouri et al [23] also found that when supercavitation occurs, the noise exhibits unipolar features. In general, research on supercavitation vehicle noise characteristics is currently lacking and mainly focuses on the low-frequency range [14,15]. It is attributed to the broad radiation spectrum and the high noise level of low-frequency domain noise.…”

Experimental Study on Influences of Surface Materials on Cavitation Flow Around Hydrofoils

“…Choi et al [18] examines a numerical fluid-material interaction approach to investigate this relationship between material pitting and cavitation field impulsive pressures. Some numerical simulations are conducted to investigate pitting formation from the combined bubble dynamics and material mechanics viewpoints [15,[19][20][21][22][23].…”

Noise from Ventilated Supercavities and its Utility for Inferring Cavity Dynamics

“…As such, this relationship presents an attractive means of inferring ventilated supercavity dynamics through its radiated noise. Previous work has studied ventilated supercavity noise either analytically or numerically and has shown that low frequency noise is expected to radiate as an acoustic monopole [1,2]. While these studies considered mainly the impingement of a gas jet on the cavity interface, Skidmore et al [3] demonstrated that the noise from pulsating cavities is related to the dominant wave on the cavity interface and radiates as a monopole source at the wave frequency.…”