LARGE EDDY SIMULATION OF WAVE-ENDUCED SEPARATION AROUND A SLENDER SURFACE-PIERCING BODY

Turbulent flows affected by free-surface have been studied in various engineering fields including naval architecture, ocean engineering, and civil engineering. Flow features of free-surface, i.e., free-surface wave, kinematic and dynamic boundary conditions, and anisotropic turbulence structure, interact with turbulent boundary layer to result in three-dimensional (3D) flow separation and wave breaking. Thanks to the recent progress in numerical methods and computational resources, analyses of turbulent flows affected by free-surface have been realized. The present study aims to examine wave-induced separation in turbulent flow around a surface-piercing body using large eddy simulation (LES). SNUFOAM, a CFD software based on an open source CFD toolkit, was used to analyze the turbulent flow field with free-surface and investigate local flow structures. The volume of fluid method with dynamic interface compression (Lee et al., 2015) was used to ensure sharp interface between air and water. The computational results were compared with the experiments in same condition first, and flow physics were investigated with the LES results. The test model is a free-surface-piercing body. The cross section is the waterplane of the Wigley hull, which is an intersection of two symmetric parabolic curves. The aspect ratio of the cross section is 1/10, to have slender cross section and prevent flow separation in two-dimensional flow. The test condition was chosen to include Froude number conditions where the wave breaking and flow separation were reported by experiments (Seo et al., 2016). By the LES analyses, interaction between the free-surface and turbulent boundary layer was identified. In the study, LES by SNUFOAM was validated and used to investigate local turbulence structure of the free-surface induced separation. Wave profile and local flow velocity were compared with experimental results and other fluid dynamic properties were also examined by the LES analysis.