Separation control with elliptical air-jet vortex generators

Experiments in Fluids, vol. 64

Abstract

Abstract The flow organisation of air-jet vortex generators (AJVGs) of elliptical cross sections and their control effectiveness on a $$24^{\circ }$$ 24∘ -compression-ramp-induced shock-wave/boundary-layer interaction was analysed on the basis of experiments at $$M_{\infty } = 2.52$$ M∞=2.52 and $$Re_{\theta _c} = 8225$$ Reθc=8225 . We investigated a circular orifice and two elliptical orifices of aspect ratios 0.5 and 2; all characterised by the same hydraulic diameter. Measurements of separation lengths from oil-flow visualisation and PIV reveal that elliptical AJVGs achieve a $$25\%$$ 25% reduction in total separation length, which constitutes a strong improvement over the $$17\%$$ 17% reduction achieved with the commonly used circular AJVGs. The jet-induced structures from elliptical AJVGs penetrate on average $$25\%$$ 25% farther into the boundary layer. However, the lateral spread is limited to a maximum value equal to the inter-jet spacing in the control array, which highlights the onset of jet/jet interactions between adjacent jets in the array. A consequence of these interactions is better flow entrainment for the elliptical cases, as observed in the mean boundary-layer velocity profiles and an improved turbulent mixing (indicated by an increase in Reynolds-shear-stress magnitude).

Authors 2

1. Deepak Prem Ramaswamy corresponding Aachen Institute of Aerodynamics Chair of Fluid Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Aerodynamics and Chair of Fluid Mechanics, RWTH Aachen University, Aachen, Germany

2. Anne-Marie Schreyer Aachen Institute of Aerodynamics Chair of Fluid Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Aerodynamics and Chair of Fluid Mechanics, RWTH Aachen University, Aachen, Germany