Flow Control of Tip/Edge Vortices

Abstract

Location, strength and structure of tip and edge vortices shed from wings and bodies can be manipulated by using flow control techniques. Flow physics of these approaches involve flow separation from the edge, roll-up into the vortex, wing flow regime, vortex instabilities, vortex-vortex interactions, and vortex-turbulence interactions. Actuators include continuous and unsteady blowing and suction, bleed, and control surfaces, which add momentum, vorticity and turbulence into the vortices. It is noted that actuation may have effects on more than one aspect of the flow phenomena. A comparative review of the control of delta wing vortices, tip vortices, and afterbody vortices is presented. The delay of vortex breakdown and the promotion of flow reattachment require different considerations for slender and nonslender delta wings, and may not be possible at all. Tip vortices can be controlled to increase the effective span, to generate rolling moment, to attenuate wing-rock, and to attenuate vortex-wing interactions. While there are different approaches for each application, opportunities for future research on turbulence ingestion, bleed, and excitation of vortex instabilities exist. Recent research also indicates that active and passive flow control can be used to manipulate the afterbody vortices in order to reduce the drag.

On the formation of three-dimensional separated flows over wings under tip effects

“…Over the years, more detailed investigations have been carried out to reveal the formation, evolution and instability mechanisms of the tip vortices (McCormick, Sherrier & Tangler 1968;Crow 1970;Francis & Kennedy 1979;Katz & Galdo 1989;Green & Acosta 1991;Devenport et al 1996;Birch et al 2004;Duraisamy 2005;Giuni 2013;Edstrand et al 2016Edstrand et al , 2018a. Based on the insights from these studies, various control techniques to alleviate the tip vortices have also been developed to reduce the induced drag and wake vortex hazards (Gursul et al 2007;Greenblatt 2012;Edstrand et al 2018b;Gursul & Wang 2018).…”

Review of self-induced roll oscillations and its attenuation for low-aspect-ratio wings

“…Similar to the vibrating wire, an unsteady forcing technique using periodic jet impulses, namely the ''synthetic jet'', was employed as an effective actuators 71 in active flow control applications for delaying stall and increasing lift, [72][73][74][75][76][77][78][79] thrust enhancement, 80 and tip vortex control. 81,82 The outcomes indicated that such an unsteady forcing technique using periodic jet impulses could energize shear layer instabilities and result in reattachment over the suction surface of the wing. Hence, the local flow excitation technique of using a synthetic jet was adopted at close to the leading edge of an AR ¼ 2 flat-plate wing in order to attenuate the self-induced roll oscillations (Figure 19).…”

Pulsed Blowing Interacting with a Leading-Edge Vortex

“…However, sustaining the leading-edge vortices is desired for aerodynamic performance increase of swept wing configurations (e.g., delta wings). In [1], the authors identified three vortex types based on their applications: tip vortices, leading-edge vortices, and wake vortices, and discussed relevant vortical flow phenomena (edge separation, vortex roll-up, vortex instabilities, and vortex interactions) and corresponding control parameters (swirl angle, pressure distribution, location of disturbance injection, frequency). Control methods targeting the manipulation of each flow feature discussed were assessed in the paper mentioned.…”

“…Control methods targeting the manipulation of each flow feature discussed were assessed in the paper mentioned. Irrespective of the actuator type (fluidic, moving-surface, or plasma actuator), the control mechanism either adds or removes vorticity, momentum, or turbulence [1].…”