Turbulent drag reduction by traveling wave of flexible wall

Zhao, Hui; Wu, Jing; Luo, Jisheng

doi:10.1016/j.fluiddyn.2003.11.001

Cited by 76 publications

(70 citation statements)

References 26 publications

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“…Recent works have addressed the application of similar traveling-waves techniques. Zhao et al (2004) have pointed out that an array of smart materials and MEMS would render a smart flexible wall the most promising candidate for effective turbu-from the Italian Ministry of University and Research through the grant PRIN 2005 on Large scale structures in wall turbulence.…”

Section: Open Questionsmentioning

confidence: 99%

Streamwise-travelling waves of spanwise wall velocity for turbulent drag reduction

Quadrio

Riccó²,

Viotti³

2009

J. Fluid Mech.

218

252

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Waves of spanwise velocity imposed at the walls of a plane turbulent channel flow are studied by Direct Numerical Simulations. We consider sinusoidal waves of spanwise velocity which vary in time and are modulated in space along the streamwise direction. The phase speed may be null, positive or negative, so that the waves may be either stationary or traveling forward or backward in the direction of the mean flow. Such a forcing includes as particular cases two known techniques for reducing friction drag: the oscillating wall technique (a traveling wave with infinite phase speed) and the recently proposed steady distribution of spanwise velocity (a wave with zero phase speed).The traveling waves alter the friction drag significantly. Waves which slowly travel forward produce a large reduction of drag, that can relaminarize the flow at low values of the Reynolds number. Faster waves yield a totally different outcome, i.e. drag increase. Even faster waves produce a drag reduction effect again. Backward-traveling waves instead lead to drag reduction at any speed.The traveling waves, when they reduce drag, operate in similar fashion to the oscillating wall, with an improved energetic efficiency. Drag increase is observed when the waves travel at a speed comparable with that of the convecting near-wall turbulence structures. A diagram illustrating the different flow behaviors is presented.

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Section: Open Questionsmentioning

confidence: 99%

Streamwise-travelling waves of spanwise wall velocity for turbulent drag reduction

Quadrio

Riccó²,

Viotti³

2009

J. Fluid Mech.

218

252

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“…Important to the focus of the present paper is the work by Zhao et al [22]. They translated the spanwise-travelling wave of body force into a space-time distribution of wall acceleration.…”

Section: Spanwise-travelling Wavesmentioning

confidence: 99%

Drag reduction in turbulent boundary layers by in-plane wall motion

Quadrio

2011

Phil. Trans. R. Soc. A.

142

112

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Drag-reduction techniques capable of reducing the level of turbulent friction through wall-parallel movement of the wall are described, with special emphasis placed on spanwise movement. The discussion is confined to active open-loop control strategies, although feedback control is briefly mentioned with regard to peculiarities of spanwise sensing and/or actuation. Theoretical considerations are first given to explain why spanwise motion is expected to be particularly effective in skin-friction drag reduction. A review of the spanwise oscillating-wall technique is given next, with discussion of recent results and prospects. Last, waves of spanwise velocity are addressed, either spanwise-or streamwise-travelling. The latter include the oscillating wall as a special case. The generalized Stokes layer-i.e. the laminar, transverse oscillating boundary layer that develops under the action of the streamwise-travelling waves-is described, and its importance in determining turbulent drag reduction discussed. Finally, open issues like energetic efficiency and its dependence on Reynolds number are addressed.

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“…Spanwise travelling waves have also been implemented with an out-of-plane motion of a flexible wall. This was first studied numerically by Zhao et al (2004). In their DNS, they observed a skin-friction drag reduction of 30 % when a forcing period of T þ ¼ 50 was used to excite the flexible wall.…”

Section: Transverse Wall Motionsmentioning

confidence: 97%

Turbulent boundary-layer control with plasma spanwise travelling waves

Whalley

Choi

2014

Exp Fluids

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Arrays of dielectric-barrier-discharge plasma actuators have been designed to generate spanwise travelling waves in the turbulent boundary layer for possible skin-friction drag reductions. Particle image velocimetry was used to elucidate the modifications to turbulence structures created by the plasma spanwise travelling waves. It has been observed that the plasma spanwise travelling waves amalgamated streamwise vortices, lifting low-speed fluid from the near-wall region up and around the peripheries of their cores to form wide ribbons of low-speed streamwise velocity within the viscous sublayer.

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Turbulent drag reduction by traveling wave of flexible wall

Cited by 76 publications

References 26 publications

Streamwise-travelling waves of spanwise wall velocity for turbulent drag reduction

Streamwise-travelling waves of spanwise wall velocity for turbulent drag reduction

Drag reduction in turbulent boundary layers by in-plane wall motion

Turbulent boundary-layer control with plasma spanwise travelling waves

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