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Aerodynamic Performance And Shedding Characteristics On A Swept-Back Wing, Shun-Chang Yen
Aerodynamic Performance And Shedding Characteristics On A Swept-Back Wing, Shun-Chang Yen
Journal of Marine Science and Technology
A NACA 0012 finite swept-back wing with a sweep-back angle of 15° was utilized to investigate the effects of angle of attack (α) and the chord Reynolds number (Rec) on the vortex shedding and aerodynamic coefficients. A hot-wire anemometer was applied to measure the vortex-shedding frequency. The projected Strouhal number (Std) at various angles of attack was determined and discussed. The relationship between Std and α is regressed as: Std = -0.0008 α + 0.209, for 22° < α < 90°. Four characteristic surface-flow patterns: separation bubble, leading-edge bubble, bubble burst, and turbulent separation were classified by changing α and Re. The behavior of surface-flow structures significantly affects the lift, drag, and moment coefficients. The lift coefficient (CL) increases with α in the separation bubble and leading-edge bubble regimes. The maximum increase rate of CL with respect to α (d(CL)/dα) is 1.52 π/rad. Occurring in the leadingedge bubble regime. However, the maximum increase rate of drag coefficient (CD) with respect to α (d(CD)/dα) is 0.49 π/rad. Occurring in the bubble-burst regime. The steep-drop of moment coefficient at stall in the unswept-wings is not observed in the swept-back wings.
Frequency Selection Of Wake Flow Behind A Naca 0012 Wing, Han-Wen Lee, Rong-Fung Huang
Frequency Selection Of Wake Flow Behind A Naca 0012 Wing, Han-Wen Lee, Rong-Fung Huang
Journal of Marine Science and Technology
The oscillating flow modes, frequency selection, and response of periodic frequency to change of characteristic flow modes behind a NACA 0012 wing model are studied experimentally. The functional relationships of the dominant mechanisms in limiting ranges of Reynolds number are justified analytically. The oscillating instabilities in wake region possess four characteristic modes: laminar, subcritical, transitional, and supercritical. In viscous effect dominated regime of laminar mode, Strouhal number is inversely proportional to Reynolds number. In inertial effect or pressure gradient dominated regime of supercritical mode, Strouhal remains constant. In regime between limiting cases, Strouhal number increases nonlinearly with Reynolds number and …