Measurements and visualisations of synthetic jets

Crook, Andrew; Wood, N. J.

doi:10.2514/6.2001-145

Cited by 59 publications

(55 citation statements)

References 5 publications

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“…al. (1999), Crook & Wood (2001), Cater & Soria (2002), and also made similar observations on 3-D flow structures and instabilities for synthetic jets issued through a circular orifice.…”

Section: I1 Synthetic Jets In Quiescent Conditionssupporting

confidence: 54%

Fundamental Experimental and Numerical Investigation of Active Control of 3-D Flows

Amitary¹,

Jansen²

2011

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A complementary experimental and numerical investigation was performed to study the 3-D flow structures and interactions of finite-span synthetic jets in a cross-flow at a chord-based Reynolds number range from 50,000 to 400,000 and angles of attack between 0 0 to 20 0 . A range of momentum coefficients was considered corresponding to six different blowing ratios in the range of 0.2 to 1.2 with an increment of 0.2 (where, the blowing ratio is defined based on the averaged outstroke jet velocity to the free-stream velocity). Experiments were conducted on two finite wings (unswept and 30 0 swept-back configurations) with a cross-sectional profile of NACA 4421, where both 2-D and stereoscopic PIV data were collected at various spanwise locations along the wing. In complement to the experiments, 3-D numerical simulations were performed, where the numerical setup not only matched the physical parameters (e.g., free-stream, blowing ratio, etc.) but also the physical dimensions (e.g., orientation and location of jet, flow control cavity including slot and chamber, etc.). Note that the numerical simulations only address one topic, which is the interaction of a single synthetic jet with a cross-flow over the unswept wing configuration, whereas the experiments included three sets of data: (1) a single finite span synthetic jet interacting with a finite unswept wing, (2) a single finite span synthetic jet interacting with a finite sweptback wing, and (3) multiple finite span synthetic jets interacting with a finite unswept wing.I.

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“…al. (1999), Crook & Wood (2001), Cater & Soria (2002), and also made similar observations on 3-D flow structures and instabilities for synthetic jets issued through a circular orifice.…”

Section: I1 Synthetic Jets In Quiescent Conditionssupporting

confidence: 54%

Fundamental Experimental and Numerical Investigation of Active Control of 3-D Flows

Amitary¹,

Jansen²

2011

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“…Synthetic jet actuators (SJA) provide a novel means of applying flow control and their potential application for the effective delay of boundary layer separation on aircraft has been the focus of intense research in recent years (Smith and Glezer, 1998;Crook and Wood, 2001;Gilarranz and Rediniotis, 2001;Glezer and Amitay, 2002). One of the reasons for this is due to their unique ability to impart additional momentum on a fluid region from which it was originally synthesised without a net mass addition, therefore requiring no bleed air supply and complex piping.…”

Section: Introductionmentioning

confidence: 99%

“…1) with a local boundary layer produces streamwise vortical structures, which are capable of delaying flow separation by entraining faster moving fluid from the freestream to the near wall region. Crook and Wood (2001) Subsequent dye visualisation by Zhong et al (2005) has shown that the interaction between a synthetic jet and a boundary layer is complex, varying from hairpin vortices that remain near to the wall to tilted vortex rings that penetrate the boundary layer as the jet-to-freestream velocity ratio increases. It has been hypothesised that the hairpin vortices may have been responsible for the formation of the streamwise vortex pair that interacted with the separation line on the circular cylinder, however further evidence is still to be sought.…”

Section: Introductionmentioning

confidence: 99%

The near wall effect of synthetic jets in a boundary layer

Jabbal

Zhong

2008

International Journal of Heat and Fluid Flow

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An experimental investigation to analyse the qualitative near wall effect of synthetic jets in a laminar boundary layer has been undertaken for the purpose of identifying the types of vortical structures likely to have delayed separation on a 2D circular cylinder model described in this paper. In the first instance, dye visualisation of the synthetic jet was facilitated in conjunction with a stereoscopic imaging system to provide a unique quasi three-dimensional identification of the vortical structures. Secondly, the impact of synthetic jet structures along the wall was analysed using a thermochromic liquid crystal-based convective heat transfer sensing system in which, liquid crystals change colour in response to the thermal footprints of a passing flow structure. Of the different vortical structures produced as a result of varying actuator operating and freestream conditions, the footprints of hairpin vortices and stretched vortex rings revealed a marked similarity with the oil flow pattern of a vortex pair interacting with the separation line on the cylinder hence suggesting that either of these structures was responsible in delaying separation. Conditions were established for the formation of the different synthetic jet structures in non-dimensional parameter space.

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“…Fig. 17 presents the mean and standard deviation of CP distributions on the airfoil upper surface according to the angle of attack at Re# = 6.67×10 5 and 1.0×10 6 . Though C P was measured by the interval of α = 1º, a couple of meaningful flow characteristics are displayed.…”

Section: Verification Of Separation Control Capability 431 Synthetimentioning

confidence: 99%

“…chers and engineers produced experimental results in jet characteristics and jet vortex ok and Wood examined the behavior of synthetic jets under a quiescent condition, a d a boundary layer [6]. The quiescent condition means flow condition without d the cross-flow condition is flow under freestream.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Computational Study on Separation Control Performance of Synthetic Jets with Circular Exit

Kim¹,

Lee²,

Jun-Hee³

et al. 2016

International Journal of Aeronautical and Space Sciences

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This paper presents experimental and computational investigations of synthetic jets with a circular exit for improving flow control performance. First, the flow feature and vortex structure of a multiple serial circular exit were numerically analyzed from the view point of flow control effect under a cross flow condition. In order to improve separation control performance, experimental and numerical studies were conducted according to several key parameters, such as hole diameter, hole gap, the number of hole, jet array, and phase difference. Experiments were carried out in a quiescent condition and a forced separated flow condition using piezoelectrically driven synthetic jets. Jet characteristics were compared by measuring velocity profiles and pressure distributions. The interaction of synthetic jets with a freestream was examined by analyzing vortical structure characteristics. For separation control performance, separated flow over an airfoil at high angles of attack was employed and the flow control performance of the proposed synthetic jet was verified by measuring aerodynamic coefficient. The circular exit with a suitable hole parameter provides stable and persistent jet vortices that do beneficially affect separation control. This demonstrates the flow control performance of circular exit array could be remarkably improved by applying a set of suitable hole parameters.

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Measurements and visualisations of synthetic jets

Cited by 59 publications

References 5 publications

Fundamental Experimental and Numerical Investigation of Active Control of 3-D Flows

Fundamental Experimental and Numerical Investigation of Active Control of 3-D Flows

The near wall effect of synthetic jets in a boundary layer

Experimental and Computational Study on Separation Control Performance of Synthetic Jets with Circular Exit

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