2025
Yin, Tingyun; Pavesi, Giorgio
Compressibility characteristics of transient sheet/cloud cavitation – a numerical survey Journal Article
In: International Communications in Heat and Mass Transfer, vol. 162, 2025, ISSN: 07351933.
Abstract | Links | BibTeX | Tags: Cavitation, Condensation Shock, Energy conversion, Shock Wave
@article{Yin2025d,
title = {Compressibility characteristics of transient sheet/cloud cavitation – a numerical survey},
author = {Tingyun Yin and Giorgio Pavesi},
doi = {10.1016/j.icheatmasstransfer.2024.108560},
issn = {07351933},
year = {2025},
date = {2025-01-01},
urldate = {2025-01-01},
journal = {International Communications in Heat and Mass Transfer},
volume = {162},
publisher = {Elsevier Ltd},
abstract = {In this study, the transient compressible sheet/cloud cavitation around the stationary blade is investigated using a Computational Fluid Dynamics (CFD) method. The instantaneous characteristics of the cavity, such as the destabilization of the sheet cavity, the transformation of the sheet topology into the cloud topology, and the process of shrinking and collapsing of the cloud cavity, are reasonably replicated. The examination of the sheet cavity reveals that the disturbance moving upwards within the cavity is a condensation shock. This shock adheres to the classical Rankine–Hugoniot jump conditions and travels at a hypersonic speed. Once the condensation shock reaches the point where the cavity separates, the sheet cavity unlocks from the surface and transitions into a cloud cavity. The cloud cavity undergoes a reduction in size as it is carried downstream and collapses in the zone of high pressure. Investigations of a small cloud cavity reveal that its collapse results in the release of immense pressure, reaching several million Pascals. Furthermore, the relationship among potential energy, kinetic energy, and pressure wave energy during the collapse of the cavity is exposed, contributing to a more comprehensive comprehension of this intricate phenomenon.},
keywords = {Cavitation, Condensation Shock, Energy conversion, Shock Wave},
pubstate = {published},
tppubtype = {article}
}
In this study, the transient compressible sheet/cloud cavitation around the stationary blade is investigated using a Computational Fluid Dynamics (CFD) method. The instantaneous characteristics of the cavity, such as the destabilization of the sheet cavity, the transformation of the sheet topology into the cloud topology, and the process of shrinking and collapsing of the cloud cavity, are reasonably replicated. The examination of the sheet cavity reveals that the disturbance moving upwards within the cavity is a condensation shock. This shock adheres to the classical Rankine–Hugoniot jump conditions and travels at a hypersonic speed. Once the condensation shock reaches the point where the cavity separates, the sheet cavity unlocks from the surface and transitions into a cloud cavity. The cloud cavity undergoes a reduction in size as it is carried downstream and collapses in the zone of high pressure. Investigations of a small cloud cavity reveal that its collapse results in the release of immense pressure, reaching several million Pascals. Furthermore, the relationship among potential energy, kinetic energy, and pressure wave energy during the collapse of the cavity is exposed, contributing to a more comprehensive comprehension of this intricate phenomenon.
2024
Zhang, Xiaowen; Tang, Fangping; Pavesi, Giorgio; Hu, Chongyang; Song, Xijie
Influence of gate cutoff effect on flow mode conversion and energy dissipation during power-off of prototype tubular pump system Journal Article
In: Energy, vol. 308, 2024, ISSN: 18736785.
Abstract | Links | BibTeX | Tags: Cut-off effect, Energy conversion, Flow mode, Large pump systems, Power-off process, Transient deviations
@article{Zhang2024b,
title = {Influence of gate cutoff effect on flow mode conversion and energy dissipation during power-off of prototype tubular pump system},
author = {Xiaowen Zhang and Fangping Tang and Giorgio Pavesi and Chongyang Hu and Xijie Song},
doi = {10.1016/j.energy.2024.132957},
issn = {18736785},
year = {2024},
date = {2024-01-01},
journal = {Energy},
volume = {308},
publisher = {Elsevier Ltd},
abstract = {Understanding the cutoff effect of gates is essential for enhancing the overall quality of the pump system's power-off process, minimizing energy losses, and reducing potential risks associated with hydraulic transients. In this study, both numerical simulations and experimental investigations were conducted on the power-off process of a tubular pump system, considering scenarios with and without gate functionality. The simulations utilized a dynamic mesh method to model gate movement, incorporated the torque balance equation to determine the real-time impeller speed, and applied the 3D-VOF method for free surface modeling in reservoirs. Power-off experiments were performed on a model pump system and a prototype pump system to validate the numerical simulation results. To elucidate the mechanism of the gate's cutoff effect, flow modes during the power-off process were categorized based on the four-quadrant static test results of the pump, revealing the deviations between transient and static characteristics. By comparing the transient flow structures of the pump system under different gate operating states, specific energy dissipation behaviors during gate cutoff were analyzed. The research findings enhance the understanding of hydraulic transients, which is essential for developing more sustainable and resilient energy systems.},
keywords = {Cut-off effect, Energy conversion, Flow mode, Large pump systems, Power-off process, Transient deviations},
pubstate = {published},
tppubtype = {article}
}
Understanding the cutoff effect of gates is essential for enhancing the overall quality of the pump system's power-off process, minimizing energy losses, and reducing potential risks associated with hydraulic transients. In this study, both numerical simulations and experimental investigations were conducted on the power-off process of a tubular pump system, considering scenarios with and without gate functionality. The simulations utilized a dynamic mesh method to model gate movement, incorporated the torque balance equation to determine the real-time impeller speed, and applied the 3D-VOF method for free surface modeling in reservoirs. Power-off experiments were performed on a model pump system and a prototype pump system to validate the numerical simulation results. To elucidate the mechanism of the gate's cutoff effect, flow modes during the power-off process were categorized based on the four-quadrant static test results of the pump, revealing the deviations between transient and static characteristics. By comparing the transient flow structures of the pump system under different gate operating states, specific energy dissipation behaviors during gate cutoff were analyzed. The research findings enhance the understanding of hydraulic transients, which is essential for developing more sustainable and resilient energy systems.
