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Influence of riblet shapes on the occurrence of Kelvin–Helmholtz rollers
Journal of Fluid Mechanics, 2021 We investigate turbulent flow over streamwise-aligned riblets (grooves) of various shapes and sizes. Small riblets with spacings of typically less than $20$ viscous units are known to reduce skin-friction drag compared to a smooth wall, but larger ...
S. Endrikat +4 more
semanticscholar +1 more source
Effect of Riblets Geometry on Drag Reduction [PDF]
Engineering and Technology Journal, 2010 The effect of longitudinal riblet surface models (U, V and semi-Circular and U with fillet corner riblets) on the performance of unsymmetrical airfoil (NACA23015) which has been investigated numerically and experimentally. Numerical investigation involve
Nibras M. Mahdi, Ikhlase M. Fayed
doaj +1 more source
Drag reduction within radial turbine rotor passages using riblets [PDF]
, 2018 In this paper, reducing the friction losses in a radial inflow turbine rotor surface by adding engineered features (riblets) is explored. Initially, computational fluid dynamics analysis was used to study the operating mechanism of riblets and to test ...
Khader, M. A., Sayma, A. I.
core +1 more source
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2011 The interaction of the overlying turbulent flow with riblets, and its impact on their drag reduction properties are analysed. In the so-called viscous regime of vanishing riblet spacing, the drag reduction is proportional to the riblet size, but for larger riblets the proportionality breaks down, and the drag reduction eventually becomes ...
García Mayoral, Ricardo +1 more
openaire +3 more sources
Riblet-generated flow mechanisms that lead to local breaking of Reynolds analogy
Journal of Fluid Mechanics, 2022 We investigate the Reynolds analogy over riblets, namely the analogy between the fractional increase in Stanton number $C_h$ and the fractional increase in the skin-friction coefficient $C_f$, relative to a smooth surface.
A. Rouhi +7 more
semanticscholar +1 more source
Direct numerical simulation of turbulent flow above zigzag riblets
AIP Advances, 2018 We investigate the drag-reducing performance of a zigzag riblet inspired by the “Miura fold” and its influence on the streamwise vortices above a wall-bounded turbulent flow through direct numerical simulations of channel flows. The employed channel wall
Kie Okabayashi +3 more
doaj +1 more source
International Journal of Thermofluids, 2022 In this paper the flow characteristics and velocity fields over the vertical axis wind turbines DU 06 W 200 airfoil developed by Delft University of Technology and some other innovative designs are examined by computational fluid dynamics (CFD ...
Omid Ali Zargar +6 more
doaj +1 more source
Direct numerical simulation for modification of sinusoidal riblets
Journal of Fluid Science and Technology, 2016 This paper proposes a new riblet configuration. A traditional sinusoidal riblet was modified with the aim of reducing pressure drag. The height of the side wall in the newly configured riblet is lowered toward the node of the sinusoidal curve to reduce ...
Kie OKABAYASHI
doaj +1 more source
Turbulent structure effects due to ordered surface roughness
Alexandria Engineering Journal, 2020 The effects of ordered surface feature in the form of converging-diverging riblets are investigated experimentally on an airfoil. Riblet sheets are applied onto the surface of NACA 0026 airfoil at a yaw angle of α=0°,±10°, Riblet height of h = 1 mm, and ...
Zambri Harun +3 more
doaj +1 more source
A Multisection Broadband Impedance Transforming Branch-Line Hybrid [PDF]
, 1995 Measurements and design equations for a two section impedance transforming hybrid suitable for MMIC applications and a new method of synthesis for multisection branch-line hybrids are reported.
Danshin, T., Kumar, S., Tannous, C.
core +2 more sources