Separation control with elliptical air-jet vortex generators

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 $$Re_{\theta _c} = 8225$$ R e θ c = 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).

Enhancing Flow Separation Control Using Hybrid Passive and Active Actuators in a Matrix Configuration

“…Reducing flow separation and recirculation in this simplified model holds significant implications for industrial flow applications. The potential of passive devices such as vortex generators [41][42][43] and active devices such as microjet actuators [44][45][46][47][48][49] to the effective ramp separation control have been successfully demonstrated in the state-ofthe-art experiments and numerical simulations. The current research adopts a smooth backward-facing ramp profile initially proposed in [40].…”