Numerical study of the effects of trailing-edge bluntness on highly turbulent hydro-foil flows

Flow-induced noise from fully submerged lifting bodies experiencing turbulent trailing edge flows continues to pose undesirable effects for many marine propulsion systems and control surfaces.This noises arises from unsteady oscillatory flow has been shown to be highly dependent on trailing edge geometry, which can also lead to unacceptable structural vibrations. This paper presents a numerical study of the influence of trailing edge geometry on the immediate wake structure and vortex shedding characteristics, which leads to the generation of flow induced tonal noise. In this study a NACA0015 airfoil is modified at the trailing-edge by vertically cutting at various locations along the axis and thereby changing Reh, where h is the height of the blunt trailing edge, while keeping the chord-length based Re fixed at 3.49× 106. The computed bluntness parameter for the onset of vortex shedding is found to agree well with published data. Also increasing the trailing edge height has a tendency to reduce the frequency of shedding. The wake formation length variations with Reh resemble that of a circular cylinder. The Strouhal number is shown to be sensitive to the changes of the near wake structure.