Drag reduction in a turbulent boundary layer on a flexible sheet undergoing a spanwise traveling wave motion

Itoh, Motoyuki; Tamano, Shinji; Yokota, Kazuhiko; Taniguchi, Shinya

doi:10.1080/14685240600647064

Cited by 50 publications

(69 citation statements)

References 38 publications

(41 reference statements)

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“…The dash-dotted line indicates the points of maximum DI at given κ x , occurring lence control. Itoh et al (2006) have succeeded in studying experimentally the spanwisetraveling wave concept in a turbulent boundary layer through a flexible sheet.…”

Section: Discussionmentioning

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: Discussionmentioning

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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“…That is, the surface moves in the wall-normal direction to form a spanwise traveling sinusoidal wave. In an experimental investigation of a flat plate boundary layer at a Reynolds number based on the momentum thickness of Re ≈ 1,000 Itoh et al [12] determined a friction drag reduction by the transversal sinusoidal wall oscillation to be about 7.5% at a spanwise excitation wavelength of λ + ≈ 3,270 wall units and a wave amplitude of y + ≈ 20 wall units.…”

Section: Introductionmentioning

confidence: 99%

Friction Drag Variation via Spanwise Transversal Surface Waves

Klumpp

Meinke

Schröder

2011

Flow Turbulence Combust

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The introduction of spanwise velocity is a promising technique to effect the near-wall turbulent flow field to influence friction drag. However, the essential physical mechanism which significantly reduces friction drag has not been understood, yet. It is the objective of this numerical study to improve the fundamental knowledge on the drag reduction mechanism. The investigation is based on spanwise traveling transversal surface waves which are applied to modify the near-wall flow field and to influence friction drag. Two actuation configurations are analyzed in detail. Compared with an unactuated flat plate boundary layer simulation the first wave setup, which represents a low frequency wave at an amplitude larger than the viscous sublayer, leads to a reduced wall-shear stress resulting in friction drag reduction of up to 9%. The second wave setup, which possesses a higher frequency and an amplitude in the range of the viscous sublayer, yields an increase of friction drag of about 8%. Unlike previous investigations which focus on excitation setups to lower friction drag, the comparison of the two wave setups in this study allows to identify the effects which on the one hand, lead to drag reduction and on the other hand, result in drag increase. That is, due to the pronounced differences the major effects determining the friction distribution are more evident. The two key features for drag reduction are the damping of the wall-normal vorticity fluctuations above the entire surface and the decrease of turbulence production. Furthermore, the effect of rearranging streamwise vorticity, which has been stated to be responsible for drag reduction, is found to occur at increasing and decreasing drag, i.e., it is not the effect that lowers the friction drag.

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“…[15][16][17] These studies in turn have lead to a new class of methods for achieving drag reduction through wall imposed traveling waves. 2,18 Another study using KL decomposition examined the energy transfer path from the applied pressure gradient to the flow through triad interaction of structures, 19,20 explaining the dynamical interaction between the KL modes. In the realm of control, KL methods have been used to produce drag reduction in a turbulent channel flow by phase randomization of the structures 21 and to understand the effect of drag reduction by controlled wall normal suction and blowing.…”

Section: Introductionmentioning

confidence: 99%

The effect of spanwise wall oscillation on turbulent pipe flow structures resulting in drag reduction

2007

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The results of a comparative analysis based upon a Karhunen–Loève expansion of turbulent pipe flow and drag reduced turbulent pipe flow by spanwise wall oscillation are presented. The turbulent flow is generated by a direct numerical simulation at a Reynolds number Reτ=150. The spanwise wall oscillation is imposed as a velocity boundary condition with an amplitude of A+=20 and a period of T+=50. The wall oscillation results in a 27% mean velocity increase when the flow is driven by a constant pressure gradient. The peaks of the Reynolds stress and root-mean-squared velocities shift away from the wall and the Karhunen–Loève dimension of the turbulent attractor is reduced from 2763 to 1080. The coherent vorticity structures are pushed away from the wall into higher speed flow, causing an increase of their advection speed of 34% as determined by a normal speed locus. This increase in advection speed gives the propagating waves less time to interact with the roll modes. This leads to less energy transfer and a shorter lifespan of the propagating structures, and thus less Reynolds stress production which results in drag reduction.

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Drag reduction in a turbulent boundary layer on a flexible sheet undergoing a spanwise traveling wave motion

Cited by 50 publications

References 38 publications

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

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

Friction Drag Variation via Spanwise Transversal Surface Waves

The effect of spanwise wall oscillation on turbulent pipe flow structures resulting in drag reduction

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