Vane-type vortex generators have proven to be well suited for passive aerodynamic control through their substantial increase in near-wall momentum. As a structurally strong variance for durable use in low-speed airfoil and turbine applications, this study looks experimentally into the low-profile triangular convergent riblet element (consisting of two short convergent vanes of triangular cross sections with 30 deg half-intervane angles) in incompressible laminar flow. The flow organization and instability within the wake of isolated vortex generators are thus investigated using hot-wire measurements over a length of 80 δ k downstream of the element, where δ k is the local boundary-layer thickness. A preliminary analysis serves first to characterize the effect of the isolated element height k across Δ ( k / δ k ) = 0.03 height adjustments for rectangular cross-section elements. A selection of three triangular element heights is subsequently investigated in detail, undergoing the following: 1) with k / δ k = 0.16 , longitudinal vortices are found to remain quasi steady and with eventual disturbance attenuation; 2) with k / δ k = 0.24 , the wake starts exhibiting strong fluctuations as it approaches critical conditions; and 3) with k / δ k = 0.48 , transition to turbulence takes place close behind the element. The switch from a varicose to a sinuous wake instability for low-profile (near-critical) configurations places the transition onset within the region of strong lateral shear.


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    Title :

    Wake Instability Behind Low-Profile “Convergent Riblet” Vortex Generators in Incompressible Laminar Flow


    Contributors:

    Published in:

    AIAA Journal ; 56 , 8 ; 3008-3023


    Publication date :

    2018-05-31


    Size :

    16 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English





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