Abstract:The control of the tip vortex, generated by a rectangular NACA 0012 wing, via tip-mounted half-delta wings (HDWs), of different slendernesses Λ, root chords cr, and deflections δ, was investigated experimentally at Re = 2.45 × 105. The results show that regardless of Λ, cr, and δ, the addition of HDWs consistently led to a diffused tip vortex. The degree of diffusion was, however, found to increase with decreasing Λ and cr. HDWs with cr ≤ 50% of the baseline-wing chord c caused a rapid diffusion of vorticity a… Show more
“…9 More recent studies consider both passive and active measures to reduce the strength and persistence of tip vortices. Passive techniques are considered by Lee and Su, 10 Lee and Choi, 11 who show experimentally that a reverse half-delta wing mounted to the tip of a NACA0012 foil resulted in a weaker tip vortex being produced. Active techniques such as the use of flaps have also been considered.…”
The flow over a flat-tipped wing at three Reynolds numbers: Re ¼ 1 Â 10 4 ; Re ¼ 4 Â 10 4 , and Re ¼ 1 Â 10 5 is investigated using direct numerical simulation. A set of grid independent results are obtained which allow for the dynamics of the tip flow, trailing vortices, and their interplay with the boundary layer dynamics to be examined in detail. The results show significant changes across the Reynolds number range. At the lowest Reynolds number, a single trailing vortex forms downstream of the trailing edge, whereas multiple vortices form over the tip at higher Reynolds numbers. The tip geometry is shown to be important with regard to the development of different structures and in the transition of the flow from laminar to turbulent. This is due to unstable shear layers, with turbulent flow becoming entrained in the vortex cores at higher Reynolds numbers. These changing vortex dynamics mean that the value of the minimum vortex core pressure and its location change with Reynolds number. This has important consequences for cavitation inception and scaling for hydrodynamic applications. The influence of the tip flow on the boundary layer is further considered by comparing the flow with that of an infinite-span wing. Analysis of the two cases shows that the tip flow reduces the effective angle of attack, which prevents the flow separation at the leading edge that is responsible for the boundary layer transition for the infinite-span case. This, in turn, changes the character of the trailing edge flow which would have significant consequences on the trailing edge noise.
“…9 More recent studies consider both passive and active measures to reduce the strength and persistence of tip vortices. Passive techniques are considered by Lee and Su, 10 Lee and Choi, 11 who show experimentally that a reverse half-delta wing mounted to the tip of a NACA0012 foil resulted in a weaker tip vortex being produced. Active techniques such as the use of flaps have also been considered.…”
The flow over a flat-tipped wing at three Reynolds numbers: Re ¼ 1 Â 10 4 ; Re ¼ 4 Â 10 4 , and Re ¼ 1 Â 10 5 is investigated using direct numerical simulation. A set of grid independent results are obtained which allow for the dynamics of the tip flow, trailing vortices, and their interplay with the boundary layer dynamics to be examined in detail. The results show significant changes across the Reynolds number range. At the lowest Reynolds number, a single trailing vortex forms downstream of the trailing edge, whereas multiple vortices form over the tip at higher Reynolds numbers. The tip geometry is shown to be important with regard to the development of different structures and in the transition of the flow from laminar to turbulent. This is due to unstable shear layers, with turbulent flow becoming entrained in the vortex cores at higher Reynolds numbers. These changing vortex dynamics mean that the value of the minimum vortex core pressure and its location change with Reynolds number. This has important consequences for cavitation inception and scaling for hydrodynamic applications. The influence of the tip flow on the boundary layer is further considered by comparing the flow with that of an infinite-span wing. Analysis of the two cases shows that the tip flow reduces the effective angle of attack, which prevents the flow separation at the leading edge that is responsible for the boundary layer transition for the infinite-span case. This, in turn, changes the character of the trailing edge flow which would have significant consequences on the trailing edge noise.
“…Note that the RDW vortex of the slender wing became singular and attained axisymmetry at x /c = 1.5 (see Figure 8(h)), which is similar to the wingtip vortex developed in the near field behind an NACA 0012 wing. 12 The variation of the critical RDW50 vortex flow parameters with x /c at α = 10° is summarized in Figure 9(a) to (e) (denoted by the ◊ symbols). Figure 8.Representative iso-ζc/u ∞ contours of the RDW vortex at selected x /c for α = 10°.…”
Section: Resultsmentioning
confidence: 99%
“…The RDWs has also been employed in the control of the wingtip vortex generated by a rectangular NACA 0012 wing at Re = 3.45 × 10 5 by Lee and Choi. 12 Lee and Choi found that, regardless of its root chord and sweep angle, the tip-mounted reverse half-delta wings always caused a rapid diffusion and breakdown of the wingtip vortex. The vortex produced by the small-chord half-delta wing interacted with the vortex from the regular NACA 0012 wing, causing both vortices to break down, which gave the benefit of reduced lift-induced drag.…”
The vortex flow and lift force generated by a 50°-sweep non-slender reverse delta wing were investigated via particle image velocimetry, together with flow visualization and force balance measurement, at Re = 11,000. The non-slender reverse delta wing produced a delayed stall but a lower lift compared to its delta wing counterpart. The stalling mechanism was also found to be triggered by the disruption of the multiple spanwise vortex filaments developed over the upper wing surface. The vortex flowfield was, however, characterized by the co-existence of reverse delta wing vortices and multiple shear-layer vortices. The outboard location of the reverse delta wing vortex further implies that the lift force is mainly generated by the wing lower surface while the upper surface acts as a wake generator. The spatial progression of the flow parameters of the vortex generated by the non-slender reverse delta wing as a function of α was also discussed.
“…In this section, the span-dominated ground effect on the wingtip vortices and the lift-induced drag generated by a (2012)). More recently, an alternative wingtip vortex control was proposed by Lee and Choi (2015) by using a tip-mounted small-chord half-delta wings (HDW) of different slenderness Λ, root chords c r , and deflections. Lee and Choi (2015) reported that, regardless of Λ and c r , the addition of a small HDW to the tip of a rectangular semi-wing at Re = 2.45 × 10 5 triggered the breakdown of the tip vortex, producing a greatly diffused and circulation flow-like tip vortex (Figure 5B) as compared to its baseline-wing Frontiers in Aerospace Engineering frontiersin.org counterpart (Figure 5A).…”
Section: Ogementioning
confidence: 99%
“…More recently, an alternative wingtip vortex control was proposed by Lee and Choi (2015) by using a tip-mounted small-chord half-delta wings (HDW) of different slenderness Λ, root chords c r , and deflections. Lee and Choi (2015) reported that, regardless of Λ and c r , the addition of a small HDW to the tip of a rectangular semi-wing at Re = 2.45 × 10 5 triggered the breakdown of the tip vortex, producing a greatly diffused and circulation flow-like tip vortex (Figure 5B) as compared to its baseline-wing Frontiers in Aerospace Engineering frontiersin.org counterpart (Figure 5A). The streamwise vorticity ζ = zw/zy − zv/zz was calculated from the vw-crossflow measurements by using a central differencing scheme to evaluate the derivatives.…”
The ground effect-induced large lift increase and lift-induced drag reduction have long been recognized and utilized in the design and construction of wing-in-ground effect (WIG) craft. Various wing planforms have been employed in WIG craft. In this study, the experimental investigations of rectangular wings and delta wings of reverse and regular configurations at low Reynolds numbers are reviewed. For rectangular wings, both chord-dominated and span-dominated ground effects on the aerodynamics, tip vortex, and lift-induced drag are reviewed. For reverse delta wings, in addition to the experimental measurements of the aerodynamics and tip vortex flow at different ground distances, passive flow control utilizing Gurney flap, cropping, and anhedral are reviewed. The impact of ground effect on delta wings is also discussed. Suggestions for future investigations applicable to each wing planform in-ground effect are provided.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
