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 downstream of the element, where is the local boundary-layer thickness. A preliminary analysis serves first to characterize the effect of the isolated element height across height adjustments for rectangular cross-section elements. A selection of three triangular element heights is subsequently investigated in detail, undergoing the following: 1) with , longitudinal vortices are found to remain quasi steady and with eventual disturbance attenuation; 2) with , the wake starts exhibiting strong fluctuations as it approaches critical conditions; and 3) with , 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.
Wake Instability Behind Low-Profile “Convergent Riblet” Vortex Generators in Incompressible Laminar Flow
AIAA Journal ; 56 , 8 ; 3008-3023
2018-05-31
16 pages
Article (Journal)
Electronic Resource
English
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