William Gordon, O. Remus Tutunea-Fatan, Evgueni Bordatchev

Abstract: Recent research has focused on the hydrodynamics of turbulent water flow over surfaces structured with various micro-scale features. Previous studies have demonstrated that streamwise triangular riblets (STR), also known as sawtooth riblets, and other riblet designs can achieve drag reduction, self-cleaning, and fouling-resistant effects. This study aimed to numerically simulate and parametrically analyze the effect of the included angle (α) of STRs on potential drag reduction. The CFD simulations conducted in this study examined the impact of design parameters on turbulent flow hydrodynamics and their influence on drag reduction performance. The analysis considered several included angle values: α = 15°, 30°, and 60°, at multiple flow velocities. Flow conditions, particularly the turbulent structures formed around the riblets, were analyzed in detail and compared with published data. CFD simulations utilized the LES WALE model with a prism and hexahedral mesh. The examination of turbulent flow patterns near riblet tips and valleys revealed characteristics consistent with previously published data for 60° STR. Furthermore, as α decreases, the range of nondimensional riblet spacing (S+) exhibiting drag-reducing effects narrows, while the range of Reynolds numbers increases. The smaller included angle analyzed was associated with maximum drag reduction (~10%) at smaller S+ values. The results of this study are expected to pave the way for developing, optimizing, and controlling advanced hydro- and aerodynamic functional surfaces.

Keywords: Turbulence, drag reduction, microsurfaces, sawtooth riblets, streamwise triangular riblets

Date Published: August 23, 2024
DOI: 10.11159/jffhmt.2024.025

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