Large Eddy Simulation and theoretical investigations of the transient cavitating vortical flow structure around a NACA66 hydrofoil

This paper mainly summarizes the recent progresses for the cavitation study in the hydraulic machinery including turbo-pumps, hydro turbines, etc.. Especially, the newly developed numerical methods for simulating cavitating turbulent flows and the achievements with regard to the complicated flow features revealed by using advanced optical techniques as well as cavitation simulation are introduced so as to make a better understanding of the cavitating flow mechanism for hydraulic machinery. Since cavitation instabilities are also vital issue and rather harmful for the operation safety of hydro machines, we present the 1-D analysis method, which is identified to be very useful for engineering applications regarding the cavitating flows in inducers, turbine draft tubes, etc. Though both cavitation and hydraulic machinery are extensively discussed in literatures, one should be aware that a few problems still remains and are open for solution, such as the comprehensive understanding of cavitating turbulent flows especially inside hydro turbines, the unneglectable discrepancies between the numerical and experimental data, etc.. To further promote the study of cavitation in hydraulic machinery, some advanced topics such as a Density-Based solver suitable for highly compressible cavitating turbulent flows, a virtual cavitation tunnel, etc. are addressed for the future works.

A review of cavitation in hydraulic machinery

Numerical simulation of three dimensional cavitation shedding dynamics with special emphasis on cavitation–vortex interaction

Numerical analysis of unsteady cavitating turbulent flow and shedding horse-shoe vortex structure around a twisted hydrofoil

Large Eddy Simulation of the Tip-leakage Cavitating flow with an insight on how cavitation influences vorticity and turbulence

Large Eddy Simulation of turbulent vortex-cavitation interactions in transient sheet/cloud cavitating flows

The objective of this paper is to apply combined experimental and computational modeling to investigate unsteady sheet/cloud cavitating flows. In the numerical simulations, a filter-based density corrected model (FBDCM) is introduced to regulate the turbulent eddy viscosity in both the cavitation regions on the foil and in the wake, which is shown to be critical in accurately capturing the unsteady cavity shedding process, and the corresponding velocity and vorticity dynamics. In the experiments, high-speed video and particle image velocimetry (PIV) technique are used to measure the flow velocity and vorticity fields, as well as cavitation patterns. Results are presented for a Clark-Y hydrofoil fixed at an angle of attack of a ¼8deg at a moderate Reynolds number, Re ¼7 � 10 5 , for both subcavitating and sheet/cloud cavitating conditions. The results show that for the unsteady sheet/cloud cavitating case, the formation, breakup, shedding, and collapse of the sheet/cloud cavity lead to substantial increase in turbulent velocity fluctuations in the cavitating region around the foil and in the wake, and significantly modified the wake patterns. The turbulent boundary layer thickness is found to be much thicker, and the turbulent intensities are much higher in the sheet/cloud cavitating case. Compared to the wetted case, the wake region becomes much broader and is directed toward the suction side instead of the pressure side for the sheet/cloud cavitation case. The periodic formation, breakup, shedding, and collapse of the sheet/cloud cavities, and the associated baroclinic and viscoclinic torques, are shown to be important mechanisms for vorticity production and modification. [DOI: 10.1115/1.4023650]

Combined Experimental and Computational Investigation of Unsteady Structure of Sheet/Cloud Cavitation

Experimental and numerical investigation of hydroelastic response of a flexible hydrofoil in cavitating flow

Comparisons of spark-charge bubble dynamics near the elastic and rigid boundaries.

Numerical study of cavitating flows in a wide range of water temperatures with special emphasis on two typical cavitation dynamics

Guoyu Wang

Papers

Large Eddy Simulation of turbulent vortex-cavitation interactions in transient sheet/cloud cavitating flows

Combined Experimental and Computational Investigation of Unsteady Structure of Sheet/Cloud Cavitation

Experimental and numerical investigation of hydroelastic response of a flexible hydrofoil in cavitating flow

Comparisons of spark-charge bubble dynamics near the elastic and rigid boundaries.

Numerical study of cavitating flows in a wide range of water temperatures with special emphasis on two typical cavitation dynamics