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

Abstract

Large Eddy Simulation and theoretical investigations of the transient cavitating vortical flow structure around a NACA66 hydrofoil, International Journal of Multiphase Flow (2014), doi: http://dx.Abstract: Compared to non-cavitating flow, cavitating flow is much complex owing to the numerical difficulties caused by cavity generation and collapse. In this paper, the cavitating flow around a NACA66 hydrofoil is studied numerically with particular emphasis on understanding the cavitation structures and the shedding dynamics. Large Eddy Simulation (LES) was coupled with a homogeneous cavitation model to calculate the pressure, velocity, vapor volume fraction and vorticity around the hydrofoil. The predicted cavitation shedding dynamics behavior, including the cavity growth, break-off and collapse downstream, agrees fairly well with experiment. Some fundamental issues such as the transition of a cavitating flow structure from 2D to 3D associated with cavitation-vortex interaction are discussed using the vorticity transport equation for variable density flow. A simplified one-dimensional model for the present configuration is adopted and calibrated against the LES results to better clarify the physical mechanism for the cavitation induced pressure fluctuations. The results verify the relationship between pressure fluctuations and the cavity shedding process (e.g. the variations of the flow rate and cavity volume) and demonstrate that the cavity volume acceleration is the main source of the pressure fluctuations around the cavitating hydrofoil. This research provides a better understanding of the mechanism driving the cavitation excited pressure pulsations, which will facilitate development of engineering designs to control these vibrations.

Investigation of Cavitation Models for Steady and Unsteady Cavitating Flow Simulation

“…Therefore, a systematic research on this topic is necessary. Recently, Large Eddy Simulation (LES) has been studied for unsteady cavitation simulations by a few researchers [35][36][37]. Some promising results have been obtained for some geometrically simplified cases.…”

Experimental and numerical investigation on cloud cavitating flow around an axisymmetric projectile near the wall with emphasis on the analysis of local cavity shedding

“…Their numerical results were in good agreement with the experiment, and presented various cavitation details and mechanisms. Moreover, some favorable results have also been published (Dittakavi et al, 2010;Huang et al, 2014;Ji et al, 2013Ji et al, , 2015Roohi et al, 2013;Wang and Ostoja-Starzewski, 2007;Wang et al, 2016aWang et al, , 2016b. Besides, some new approaches are developed to simulate the cavitating flow and get favorable results (Ma et al, 2010;Ma et al, 2017).…”

Numerical Analysis of the Turbulent Flow Structure Induced by the Cavitation Shedding using LES

“…Existing cavitation models compute the overall behavior of cavitating flows which implies that the major goal of a cavitation model should be to predict the onset, growth, and collapse of bubbles in cavitating flows. (Ji et al 2014) (Zhao, Wang, and Huang 2016a). Depending on the operating conditions many types of cavitation can be observed on a cavitating hydrofoil: bubble, sheet, cloud and vortex cavitation.…”

“…Their focus was to generate sheet cavities that are three-dimensional in character similar to ones that occur on ship propellers. Based on experimental observation (Ji et al 2014). They domenstrates that the shedding is periodic, constant in its shedding frequency, and always includes the same macro structural collapse (Foeth et al 2006).…”

“…Originally proposed by (Smagorinsky 1963) and refined by many researchers, the large eddy simulation (LES) approach give better predictions of larger-scale turbulent eddies for modeling the cavitating flow. (Dittakavi, Chunekar, and Frankel 2010);(Yu, X., Huang; C., Du, T.; Liao, L.; Wu, X.; Zheng, Z.; Wang 2014); (Ji et al 2014); (Ji et al 2013(Ji et al , 2014; ; ; (Amromin et al 2006); (Zhao, Wang, and Huang 2016b). …”