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전우평(Woo-Pyung Jeon),김훈도(Hoondo Kim),최해천(Haecheon Choi) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The aerodynamic role of cactus grooves is experimentally investigated in a wind tunnel by measuring drag, surface pressure and near-wall streamwise velocity. The cactus is modeled by mounting spanwise triangular grooves on a circular cylinder. The height of the span wise groove is 7% of outer diameter of the model, which is the biological exterior feature of Saguaro cactus. The Reynolds numbers based on the free-stream velocity and model diameter are 126000~410000. The spanwise grooves reduce the drag by 13% compared to a smooth circular cylinder, and the drag remains almost constant as the Reynolds number increases. The separation point of the flow over the grooved cylinder is fixed at θ=90° regardless of the Reynolds number investigated. The shear-layer instability induced by the local separation bubble increases turbulent production over the grooved surface, which generates strong near-wall momentum and leads to delay of main separation point.