Abstract
The present study focuses on the numerical simulation of unsteady cavitating flow around a plane-convex hydrofoil with a semi-cylindrical obstacle, which is based on the cavitation-erosion experiment perform at LMH-EPFL using the vortex cavitation generator tunnel. The turbulence model k-ω SST SAS method, which presents advantages in terms of computational consumption and reproduction of the phenomenon, has been applied in OpenFOAM version 4 to reproduce the unsteady behavior of cavitating flow. Additionally, the Zwart-Gerber-Belamri (ZGB) cavitation model has been applied, based on a previous work where this model was implemented in OpenFOAM. The model is based on Rayleigh Plesset equation, which considers small cavities with changes of void fraction for condensation and vaporization and using empirical calibration numbers based on previous research. Regarding the mesh development, the present work explores two configurations of grid mesh containing hexahedra (hex) and split-hexahedra (split-hex) automatically generated from triangulated surface geometries based on previous numerical studies. The aforementioned method aims to optimize computational demand and phenomenon reproducibility. Results show that the unsteady cavitating flows behavior has been reproduced with good accuracy and shows special details which are important for erosion studies in futures works.
Highlights
Hydroelectric power plants are an ecologically and economically method to solve problems related to energy security and energy deficit [1][2]
The present study focuses on the numerical simulation of unsteady cavitating flow around a plane-convex hydrofoil with a semi-cylindrical obstacle, which is based on the cavitationerosion experiment perform at LMH-EPFL using the vortex cavitation generator tunnel
The boundary condition for top and bottom is “slip” whereas for obs1 and w1 “noSlip”. This was based on the “Numerical simulation of cavitation erosion on a NACA0015 hydrofoil based on bubble collapse strength” performed by Hidalgo et al [24]
Summary
Hydroelectric power plants are an ecologically and economically method to solve problems related to energy security and energy deficit [1][2]. The adverse pressure gradient in the posterior area of the cavity is primarily responsible for the generation of the reentrant jet [12] These studies showed the structure of unsteady flow and the evolution of cloud cavitation patterns. It was concluded that the cavitation detachment and the violent collapse of the cavity, when the structures enter the region of highest pressure near the vicinity of the solid surface is the area most affected by vibrations and erosion. In this context, computational fluid dynamics (CFD) is shown as a fundamental tool in the study of cavitation, due to the costs and limitations of the experiments [14]. The results are compared graphically with studies conducted by Hidalgo V. [16] and Escaler X. [11]
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