The Flow Structure Produced by Pulsed-jet Vortex Generators in a Turbulent Boundary Layer in an Adverse Pressure Gradient

Kostas, J.; Foucaut, Jean-Marc; Stanislas, Michel

doi:10.1007/s10494-007-9069-3

Cited by 22 publications

(15 citation statements)

References 25 publications

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“…Hence, the structures produced at the highest pulse frequency could be considered quasi-steady. This has recently been observed in PIV measurements of the same flow by Kostas et al [17]. A plot of the intensity of the wall shear stress fluctuations (τ /τ ) as a function of duty cycle for each configuration and pulse actuation frequency is shown in Fig.…”

Section: Fluctuating Shear Stresssupporting

confidence: 74%

“…It is important to note that this result is based upon the measurement of the mean wall shear stress far downstream of the actuators. The development of structures and subsequent effect on other flow quantities close to the actuators has been shown to be different for pulsed and continuous jets, especially during the transient phases of the pulse cycle [17].…”

Section: Mass Flow Dependencementioning

confidence: 99%

“…Pulsing not only offers the possibility of saving mass flow (which would most likely be obtained from the compressor stages of the engines) but also exploits the pulsing which has been shown to create an enhanced vortex generation mechanism and leads to elevated turbulent stresses over continuous jets [17]. Varying the duty cycle (at a fixed VR) varied the mass flow rate with the direct consequence of a variation of wall shear stress gain.…”

Section: Practical Implicationsmentioning

confidence: 99%

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The effects of pulse frequency and duty cycle on the skin friction downstream of pulsed jet vortex generators in an adverse pressure gradient turbulent boundary layer

Kostas

Foucaut

Stanislas

2009

Aerospace Science and Technology

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Section: Fluctuating Shear Stresssupporting

confidence: 74%

Section: Mass Flow Dependencementioning

confidence: 99%

Section: Practical Implicationsmentioning

confidence: 99%

See 1 more Smart Citation

The effects of pulse frequency and duty cycle on the skin friction downstream of pulsed jet vortex generators in an adverse pressure gradient turbulent boundary layer

Kostas

Foucaut

Stanislas

2009

Aerospace Science and Technology

Self Cite

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“…The passive control methods delay the flow separation in the retreating region through the blade geometrical modification and are always in operation, regardless of need or performance penalty. Passive control devices such as Pulse Vortex Generator Jets (PVGJs) [15][16][17], Direct Synthetic Jet (DSJ) [18,19], Rod Vortex Generator (RVG) [20] and Vortex Trap Concept [21][22][23]were designed to generate vortices to reduce flow separation of the retreating blade at a high angle of attack. On the other hand, the second method controls flow by adding energy or momentum to the flow in a regulated manner.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic prediction of helicopter rotor in forward flight using blade element theory

Yaakub¹,

Wahab²,

Abdullah³

et al. 2017

J. MECH. ENG. SCI.

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In this study, the helicopter blade in forward-flight condition was investigated. The blade element theory (BET) was used throughout this analysis to investigate the angle of attack variations at the blade cross sections, lift distribution along the blade and effects of increasing helicopter speed. Prouty's helicopter data was used to validate the analysis results. In this analysis, the helicopter blade was divided into 50 equally spaced elements and the azimuth ψ was set at 7.2° for each movement of the blade. The helicopter speed of 80 m/s was considered. The analysis revealed that the computation results were in good agreement with Prouty's diagram. Furthermore, it was also evident that in the case of a helicopter in forward-flight condition, the blade at retreating side was generally at low angle of attack and experienced low lift, in contrast to the blade at advancing side. The increment of the helicopter speed affected the lift distribution along the blade. The reverse flow area was widened two times from that given by the original Prouty's diagram. In addition, it was proven that each helicopter has its own speed limit called velocity never exceed (VNE). It was also shown that BET is important in conducting the analysis to modify the helicopter blade design for the aerodynamic characteristics' improvement as well as stability and general performance enhancement for the helicopter.

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“…In the last few decades VGs have been widely researched and new concepts of non-solid VGs-such as synthetic jets or pulsed jets (Lin 2002;Wiltse and Glezer 1993;Amitay et al 1998;McManus et al 1994;Kostas et al 2007)-have been proposed. It has been demonstrated that active VGs provide similar benefits as passive VGs, but with a major added advantage: when they are not functional, there is no increment in the parasitic drag (Paul et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Improvement of Wind Turbine Blade Performance by Means of Rod Vortex Generators

et al. 2016

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Wind turbines are complex energy conversion fluid-flow machines which entail coupled aero-mechanical issues. From an aero-acoustical point of view, wind turbine blades present two main problems: first, a reduced aerodynamic performance due to flow separation, and second, the level of noise emissions. Flow separation appears on the blade as a result of high angles of attack causing a decrease in the aerodynamic efficiency. In this chapter, the application of rod vortex generators (RVGs) to control and decrease the flow separation-by the creation of streamwise vorticity on the blade-is presented. The NREL Phase VI wind turbine rotor and the S809 airfoil are used as reference cases. The validation of NREL Phase VI model rotor against experimental data is found to be satisfactory. A study into the effects of RVGs' chordwise location and spanwise distance is presented for selected cases and a range of inflow conditions. It is shown that the proposed RVGs lead to an improvement of the aerodynamic performance, and can be successfully applied by the wind energy industry. IntroductionThe wind energy sector has experienced rapid growth in the last few decades. The developments in the materials science, engineering and allied fields have ushered in turbines of increasing sizes; turbines with rotor diameters of up to 160 m (Vestas V164 8 MW) have been developed, and the current trend of increasing sizes is expected to continue in the future (Bak et al. 2012).The increasing sizes of wind turbines pose new challenges for engineers. One particular challenge is that large rotor dimensions result in non-uniform inflow conditions along the blade span-which leads to increased flow separation even after the application of traditional flow control approaches. As a consequence of

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The Flow Structure Produced by Pulsed-jet Vortex Generators in a Turbulent Boundary Layer in an Adverse Pressure Gradient

Cited by 22 publications

References 25 publications

The effects of pulse frequency and duty cycle on the skin friction downstream of pulsed jet vortex generators in an adverse pressure gradient turbulent boundary layer

The effects of pulse frequency and duty cycle on the skin friction downstream of pulsed jet vortex generators in an adverse pressure gradient turbulent boundary layer

Aerodynamic prediction of helicopter rotor in forward flight using blade element theory

Improvement of Wind Turbine Blade Performance by Means of Rod Vortex Generators

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