Large eddy simulation of a sheet/cloud cavitation on a NACA0015 hydrofoil

Abstract

A single fluid model of sheet/cloud cavitation is developed and applied to a NACA0015 hydrofoil. First, a cavity formation model is set up, based on a three-dimensional (3D) non-cavitation model of Navier-Stokes equations with a large eddy simulation (LES) scheme for weakly compressible flows. A fifth-order polynomial curve is adopted to describe the relationship between density coefficient ratio and pressure coefficient when cavitation occurs. The Navier-Stokes equations including cavitation bubble clusters are solved using the finite-volume approach with time-marching scheme, and MacCormack's explicit-corrector scheme is adopted. Simulations are carried out in a 3D field acting on a hydrofoil NACA0015 at angles of attack 4°, 8°and 20°, with cavitation numbers r = 1.0, 1.5 and 2.0, Re = 10 6 , and a 360 · 63 · 29 meshing system. We study time-dependent sheet/cloud cavitation structures, caused by the interaction of viscous objects, such as vortices, and cavitation bubbles. At small angles of attack (4°), the sheet cavity is relatively stable just by oscillating in size at the accumulation stage; at 8°it has a tendency to break away from the upper foil section, with the cloud cavitation structure becoming apparent; at 20°, the flow separates fully from the leading edge of the hydrofoil, and the vortex cavitation occurs. Comparisons with other studies, carried out mainly in the context of flow patterns on which prior experiments and simulations were done, demonstrate the power of our model. Overall, it can snapshot the collapse of cloud cavitation, and allow a study of flow patterns and their instabilities, such as ''crescent-shaped regions.'' Ó

Feasibility study into a computational approach for marine propeller noise and cavitation modelling

“…This, in turn, implies that the input data to the acoustic analogy becomes corrupted, making its predictions incorrect. Studies involving compressible flow simulations, such as those by Wang & Ostoja-Starzewski (2007) and Seo et al (2008), have reported that far more physical results may be obtained if the incompressible assumption is not invoked. However, undertaking compressible simulations of marine problems is still an uncommon practice and, reportedly, may be associated with significantly increased computational costs (Wikstrom 2006, Godderidge et al 2009, Budich et al 2015, Fujiyama 2015.…”

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).…”

Effect of mesh resolution on large eddy simulation of cloud cavitating flow around a three dimensional twisted hydrofoil

“…LES with the WALE SGS stress model was adopted to calculate the cavitation shedding and horse-shoe structures by Ji et al [22][23][24] and Huang et al [25]. A single fluid model of sheet/cloud cavitation was developed and applied to a NACA0015 hydrofoil by Wang [26]. The physical mechanism for the cavitation induced pressure fluctuations around a NACA66 hydrofoil was analyzed by Ji et al [27].…”