Cavitation occurs as the fluid pressure is lower than the vapor pressure at a local thermodynamic state and may result in huge damage to the hydraulic machinery. Cavitation in cryogenic liquids is widely present in contemporary science, and the characteristics of cryogenic cavitation are quite different from those of water due to thermal effects and strong variations in fluid properties. The present paper reviews recent progress made toward performing experimental measurements and developing modeling strategies to thoroughly investigate cryogenic cavitation. The thermodynamic properties of cryogenic fluids are first analyzed, and different scaling laws for thermal effects estimation are then introduced. As far as cryogenic cavitation experimental research is concerned, the progress made in the cavitation visualization and cavity dynamics and the synchronous measurements of the multi-physical field are mainly introduced. As for the study on numerical simulation of cryogenic cavitation, the commonly used cavitation models and turbulence models are, respectively, classified and presented, and the modifications and improvements of the cavitation model and turbulence model for thermal effect modeling of cryogenic cavitation are examined. Then, several advances of critical issues in cryogenic fluid cavitation research are reviewed, including the influences of thermal effects, unsteady shedding mechanisms, cavitation–vortex interactions, and cavitation-induced vibration/noise. This review offers a clear vision of the state-of-the-art from both experimental and numerical modeling viewpoints, highlights the critical study developments and identifies the research gaps in the literature, and gives an outlook for further research on cryogenic cavitation.

Investigation on cavitation features in cryogenic liquids is of great importance to rocket engine design due to their complicated physics. This paper experimentally investigates the characteristics of unsteady liquid nitrogen (LN₂) cavitating flow through a transparent venturi tube with image processing techniques. The numerical simulations based on the computational fluid dynamic approach are also performed to help explain the mechanisms. A pressure ratio (P_r) associated with the inlet and the outlet subcooling is found to have a linear relationship with the cavitation number. The nondimensional thermal effect parameter derived from the single bubble dynamics is used to quantify thermal effect intensity. The cavity length derived from standard derivation results has an inversely linear relation with P_r, and there exists an inflection point of the pressure ratio (P_rc) below which the cavity length growth rate is relatively larger. The effects of the bulk temperature on the magnitude of P_rc are numerically investigated, which reveals that P_rc increases as the liquid temperature increases. The oscillating frequencies of the sheet and cloud cavitating flow are also analyzed according to two Strouhal numbers based on cavity length (St_c) and venturi throat diameter (St_d), respectively. For cloud cavitation, St_c lies in between 0.30 and 0.40 for all P_r values, while for sheet cavitation, it decreases to 0.04–0.08. Besides, in the cloud cavitation region, St_d increases linearly with P_r but has a weak relation with $\sum \cdot \sqrt{C/u_{th}^3}$ . It is also found that with increased values of $\sum \cdot \sqrt{C/u_{th}^3}$ , the transition point of P_r from sheet cavitation to cloud cavitation is delayed.

In this paper, the Large Eddy Simulation (LES) combined with the Schnerr–Sauer cavitation model and the permeable Ffowcs Williams–Hawkings (FW-H_pds) acoustic analogy approach are introduced to study the unsteady cavitation behaviors and the radiated noise characteristics of the transient liquid nitrogen (LN₂) cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil. Satisfactory agreement is obtained between the numerical predictions and experimental measurements. The cavitation noise is predicted based on the sound radiation theory for spherical bubbles and compared with the sound pressure levels of non-cavitating flow from the FW-H_pds equation. It is found that the cavity volume acceleration is directly responsible for driving the generation of cavitation noise, and the sound pressure caused by the development of LN₂ cavitation is shown to vary with the periodic pulsing cavity volume evolution, indicating a strong link between cavity evolutions and radiated noises. The transient cavitation structures of the sheet and cloud cavitation are well captured, and the evolution features of the cavities and vortex structures are analyzed in detail. The collapse of the detached small cloud cavity downstream is the main mechanism for generating intense acoustic impulses for both sheet and cloud cavitation. While the strong interaction between the re-entrant jet and the main flow results in violent pressure fluctuations, and thus produces instantaneous extreme dipole noise, which accounts for another distinctive mechanism to induce intense acoustic impulses for cloud cavitation, the presented study provides a deep understanding of the nature of cavitation-dominated noise for cryogenic cavitating flow.

Poppet valves are basic components of many manufacturing operations and industrial processes. The valve plug will withstand unbalanced pressure during the

An investigation into the shedding mechanism of cloud cavitation is of great importance to understand the cavitation dynamics for cryogenic liquids. In this study, the dynamic processes of liquid nitrogen cavitating flows in a convergent–divergent (C–D) square nozzle under various operating conditions are experimentally investigated. Simultaneous measurements of cavity dynamics and the velocity variations in the cavitation region are implemented by introducing a high-speed camera and laser Doppler velocimetry (LDV). Several cavitation numbers are realized by changing the inflow velocity and thus the throat velocity. The specific shedding characteristics as well as the mechanism of the re-entrant jet and condensation shock are qualitatively analyzed for each case by examining high-speed photographs. In addition, a three-dimensional numerical model based on the large Eddy simulation (LES) is employed to further explore the re-entrant jet/condensation shock-dominated cavity shedding dynamics. The numerical results are in good agreement with the experimental results by comparing the temporal cavitation regime distributions and the velocity variations at the same positions. The velocity of the re-entrant jet at the end of the cavity is about −4 to −5 m/s and decreases along the upstream direction. The re-entrant jet and the condensation shock are found to be the dominant mechanism for the shedding of cloud cavitation when σ = 0.497 and σ = 0.386, respectively. The shedding mechanism revealed by the combined experimental and numerical studies offers a deeper understanding of the unsteady shedding of cloud cavitation for cryogenic fluids.