Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators

Godard, Gilles; Stanislas, Michel

doi:10.1016/j.ast.2005.11.007

Cited by 285 publications

(192 citation statements)

References 13 publications

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“…There are also other analogies between the leading edge patterns and the counter-rotating vortex generators. For example, both of them produce streamwise vortices which increase in size further downstream (Godard and Stanislas 2006).…”

Section: Effect Of the Holes On The Vortex Structure And Flow Stabilitymentioning

confidence: 99%

“…Additionally, the heat transfer rate may also increase due to the mixing enhanced by the streamwise counter-rotating vortices particularly near the wall zone (Webb and Kim 2005). Vortex generators (VGs) are frequently utilized to generate streamwise vortices by making discontinuity and shear forces in the flow (Lin et al 1991;Godard and Stanislas 2006). Many studies have examined and optimized the VGs in term of shape, size, orientation and configuration.…”

Section: Introductionmentioning

confidence: 99%

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Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

Hasheminejad

Mitsudharmadi

Winoto

et al. 2016

J Vis

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A series of flow visualizations were conducted to qualitatively study the development of streamwise counter-rotating vortices over a flat plate induced by triangular patterns at the leading edge of a flat plate. The experiments were carried out for a Reynolds number based on the pattern wavelength (λ) of 3080. The results depict the onset, development and breakdown of the vortical structures within the flat plate boundary layer. Moreover, the effect of one spanwise array of holes with diameter of 0.2λ (=3 mm) was examined. This investigation was done on two different flat plates with holes placed at the location x/λ=2 downstream of the troughs and peaks. The presence of holes after troughs does not show any significant effect on the vortical structures. However, the plate with holes after peaks noticeably delays the vortex breakdown. In this case, the "mushroom-like" vortices move away from the wall and propagate downstream with stable vortical structures. The vortex growth is halted further downstream but start to tilt aside.

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Section: Effect Of the Holes On The Vortex Structure And Flow Stabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

Hasheminejad

Mitsudharmadi

Winoto

et al. 2016

J Vis

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“…Pearcey (1961) observed that for common-flow up configurations, the vortices initially move closer together and then lift away from the wall. This can cause the vortex pairs to lift outside of the boundary layer region, so that they are no longer effective at re-energising the boundary layer fluid, although the amount of lifting depends somewhat on the external pressure gradient (Godard and Stanislas 2006a). In common-flow down configurations, the vortices initially move laterally apart whilst remaining close to the surface until the vortices from one pair begin to interact with the vortices from adjacent pairs.…”

Section: Introductionmentioning

confidence: 99%

Dielectric-barrier-discharge vortex generators: characterisation and optimisation for flow separation control

Jukes

Choi

2011

Exp Fluids

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We investigated the use of dielectric-barrierdischarge plasma actuators as vortex generators for flow separation control applications. Plasma actuators were placed at a yaw angle to the oncoming flow, so that they produced a spanwise wall jet. Through interaction with the oncoming boundary layer, this created a streamwise longitudinal vortex. In this experimental investigation, the effect of yaw angle, actuator length and plasma-induced velocity ratio was studied. Particular attention was given to the vortex formation mechanism and its development downstream. The DBD plasma actuators were then applied in the form of co-rotating and counter-rotating vortex arrays to control flow separation over a trailing-edge ramp. It was found that the vortex generators were successful in reducing the separation region, even at plasma-to-freestream velocity ratios of less than 10%.

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“…Many studies have presented (nominal) guidelines for optimizing the effect of forced mixing for these passive devices for varying geometries and flow conditions (see e.g. Schubauer & Spangenberg 1960;Pearcey 1961;Godard & Stanislas 2006). Further, a review on low-profile vortex generators was written by Lin (2002).…”

Section: Introductionmentioning

confidence: 99%

“…However, the development of stereoscopic particle image velocimetry (SPIV) allows non-intrusive instantaneous measurement realizations of the flow in a plane and is the predominating measurement technique for these investigations today (see e.g. Godard & Stanislas 2006;Velte, Hansen & Cavar 2008). SPIV measurements in spanwise planes downstream of a single rectangular vortex generator on a flat plate have been conducted and investigated.…”

Section: Introductionmentioning

confidence: 99%

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

2009

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Embedded vortices in turbulent wall-bounded flow over a flat plate, generated by a passive rectangular vane-type vortex generator with variable angle β to the incoming flow in a low-Reynolds-number flow (Re = 2600 based on the inlet grid mesh size L = 0.039 m and free stream velocity U ∞ = 1.0 m s −1 ), have been studied with respect to helical symmetry. The studies were carried out in a low-speed closed-circuit wind tunnel utilizing stereoscopic particle image velocimetry (SPIV). The vortices have been shown to possess helical symmetry, allowing the flow to be described in a simple fashion. Iso-contour maps of axial vorticity revealed a dominant primary vortex and a weaker secondary one for 20 • 6 β 6 40 • . For angles outside this range, the helical symmetry was impaired due to the emergence of additional flow effects. A model describing the flow has been utilized, showing strong concurrence with the measurements, even though the model is decoupled from external flow processes that could perturb the helical symmetry. The pitch, the vortex core size, the circulation and the advection velocity of the vortex all vary linearly with the device angle β. This is important for flow control, since one thereby can determine the axial velocity induced by the helical vortex as well as the swirl redistributing the axial velocity component for a given device angle β. This also simplifies theoretical studies, e.g. to understand and predict the stability of the vortex and to model the flow numerically.

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Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators

Cited by 285 publications

References 13 publications

Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

Dielectric-barrier-discharge vortex generators: characterisation and optimisation for flow separation control

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

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