Flow pattern, aerodynamic performance, vortex-shedding frequency and turbulence intensity were compared between a single wing-blade and two tandem wing-blades for various Reynolds numbers (Re), gap ratios (g*) and angles of attack (α). The wing-blade profile was NACA 0012 which was fabricated from stainless steel. The effects of α comprised the effect of the angle of attack of the front wing-blade (α 1) and that of the rear wing blade (α 2). Flow behaviors and flow patterns were visualized using the smoke-wire method. The vortex-shedding frequency and turbulence intensity were measured using a hot-wire anemometer. The smoke-streak flow pattern around the single wing-blade was categorized as five characteristic flow patterns, which are attached surface flow, instability wave in wake, vortical wake, and separation from near-leading-edge and bluff-body wake. The smoke-streak flow patterns around the two tandem wing-blades (changing α 1 and g*) were classified as attached flow, separation, turbulent flow and vortex street for α2 = 0°. The flow patterns for α1 = 0° (with varying α2 and g*) were attached flow, vortical wake, bluff-body wake and bi-vortex street. As α 1, α 2 and g* changed, the flow patterns were classified as attached flow, vortical wake, bluff-body wake and turbulent flow. The characteristics of St1, St2, I1 and I2 parameters (measured around the tandem wing-blades) were compared with Sts and Is (detected around the single wing-blade). The aerodynamic performance was measured using a six-force balancer. For α2 ≥30°, the maximum lift coefficient (CL was reached at g* = 0 because of the equivalent flap effect that was caused from the existence of rear wing-blade.


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    Title :

    Flow patterns and characteristics of two tandem wing-blades at low Reynolds numbers


    Contributors:
    San, Kuo C. (author) / Hung, Sheng C. (author) / Yen, Shun C. (author)


    Publication date :

    2014


    Size :

    16 Seiten, Bilder, Tabellen, 18 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English