Experimental investigations of the vortex flow on delta wings at high incidence

Stahl, W. H.; Mahmood, M. Ansar; Asghar, Asad

doi:10.2514/3.11023

Cited by 52 publications

(37 citation statements)

References 6 publications

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“…The asymmetry observed by Bird 15 may be due to such slight changes in the separation position on the round leading edge of his experimental models. This agrees with the experimental results of Lim et al 32 on flat-plate wing of ogive-shaped planform with sharp/rounded tip and edges, which showed that the leading-edge geometry played a crucial role in developing the vortex asymmetry rather than the apex geometry as suggested by Stahl et al 12 Figure 12 plots the eigenvalues of the asymmetric vortex system versus the right separation angle 0 . The right vortex is stable when 0 is between 89.2°and 92.7°and unstable otherwise.…”

Section: Elliptic Conessupporting

confidence: 89%

“…These findings agreed with the known experimental observations by Stahl, 8 Ng,9 and Asghar et al 10 of the stabilizing effect of fins of sufficient heights in their experiments. At the same time, the findings also clarified the conflict between the experimental observations by Shanks 11 and Stahl et al 12 Shanks 11 reported asymmetric vortices in his flat-plate delta wing, whereas Stahl et al 12 observed none until vortex breakdown in their tests. It was found that Shanks' model 11 differed from that by Stahl et al 12 in that Shanks' model had a short center spline which, according to the analysis in Ref.…”

Section: Introductionsupporting

confidence: 70%

“…Using tuft-grid surveys at low speeds, Bird 15 observed appearance of asymmetric vortex flow over a slender flatplate delta wing model with a rounded leading edge and a semi-apex angle ϭ3.5°when ␣у15°, which disagrees with the observations by Stahl et al, 12 who used wing models with sharp leading edges. Bird 15 did not provide details of his wing profile or measurement of separation angles.…”

Section: Elliptic Conesmentioning

confidence: 70%

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Stability of symmetric and asymmetric vortex pairs over slender conical wings and bodies

2004

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Theoretical analyses are presented for the stability of symmetric and asymmetric vortex pairs over slender conical wings and bodies under small perturbations in an inviscid incompressible flow at high angles of attack and sideslip. The three-dimensional problem of a pair of vortices over slender conical wings and bodies is reduced to a problem in two dimensions by using the conical flow assumption and classical slender-body theory. The stability of symmetric and asymmetric vortex pairs over flat-plate delta wings, slender circular cones, and elliptic cones of various thickness ratios are examined. Results are compared with available experimental data.

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Section: Elliptic Conessupporting

confidence: 89%

Section: Introductionsupporting

confidence: 70%

Section: Elliptic Conesmentioning

confidence: 70%

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Stability of symmetric and asymmetric vortex pairs over slender conical wings and bodies

2004

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“…Figure 7 demonstrates that the vortex core pressure P c is always lower for the case with jets than that for the case without jets. From vortex theory, the lower a vortex core pressure and the greater a vortex core axial velocity are, the more stable the vortex is [25][26][27][28]. It can be concluded that the trailing-edge jets tend to stabilize the leading-edge primary vortices.…”

Section: Resultsmentioning

confidence: 99%

Numerical simulation of flow over delta wing with trailing‐edge jet at high angle of attack

Zhang

Tang

2004

Numerical Meth Engineering

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SUMMARYThe incompressible Reynolds-averaged Navier-Stokes equations, together with a modified mixing length algebraic turbulence model, are solved to simulate the flow over a delta wing with trailing-edge jets at high angles of attack. An artificial compressibility method and a Beam-Warming implicit approximate factorization scheme are employed to discretize the equations. The computed results indicate that trailing-edge jets tend to not only decrease the pressure but also increase the velocity at the cores of the streamwise primary vortices. This moves the vortex breakdown locations aft and stabilizes the vortical flow. As a result, the jets lead to a decreased pressure on the upper wing surface and an increased pressure on the lower wing surface, thereby increasing the overall lift. Computations further show that as the exit area of the trailing-edge jets is enlarged, or, as the jets are deflected downward, the above-mentioned effects become more pronounced.

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“…Polhamus 30 reported that initially symmetric leading-edge vortices over slender delta wings became asymmetric at high angles of attack before vortex breakdown. However, Stahl et al 31 indicated no strong asymmetry was observed before vortex breakdown in their experiments. Though several theories on the mechanism of vortex breakdown were proposed, there is still some uncertainty with regard to the interpretation of this phenomenon, as indicated in the review by Escudier.…”

Section: Introductionmentioning

confidence: 95%

A combined experimental and analytical investigation of the vortex stability over sharp-edged slender bodies

2007

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A combined experimental and analytical investigation is conducted to assess the stability of the symmetric vortex pair over three different sharp-edged slender bodies at high angles of attack. The analysis is based on a previously developed eigenvalue stability method. Corresponding experimental studies involving flow visualization in the water tunnel, force and pressure measurement in the wind tunnel are carried out. The angles of attack tested range from 15°to 40°. Overall, the experiments confirm the stability behaviors as determined from the analysis. The analytical solutions indicate that an absolute type of instability is the mechanism for the breakdown of symmetry of the vortex flow over slender conical bodies at high angles of attack. Both the experiments and the analysis reveal that a sharp-edged slender body with a smaller volume on the leeward side and a bigger volume on the windward side increases the overall stability of the symmetric vortex pair. A shape with extended sharp edges in the outboard direction on its sides further enhances the stability of the vortex pair. The analytical method can be a useful tool for exploring shapes that favor stability or instability.

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Experimental investigations of the vortex flow on delta wings at high incidence

Cited by 52 publications

References 6 publications

Stability of symmetric and asymmetric vortex pairs over slender conical wings and bodies

Stability of symmetric and asymmetric vortex pairs over slender conical wings and bodies

Numerical simulation of flow over delta wing with trailing‐edge jet at high angle of attack

A combined experimental and analytical investigation of the vortex stability over sharp-edged slender bodies

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