A fundamental limit on the balance of power in a transpiration-controlled channel flow

Bewley, Thomas

doi:10.1017/s0022112008004886

Cited by 55 publications

(43 citation statements)

References 6 publications

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“…The absolute maximum of drag reduction for A + = 12 is found to be R = 0.48, which is not far from relaminarization. (At this value of Re, about one-quarter of the friction drag is the laminar contribution, which has been demonstrated by Bewley [25] to be the true minimum one can reach. At lower Re, waves at A + = 12 have been found to relaminarize the flow.…”

Section: Streamwise-travelling Wavesmentioning

confidence: 57%

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

Quadrio

2011

Phil. Trans. R. Soc. A.

143

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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Section: Streamwise-travelling Wavesmentioning

confidence: 57%

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

Quadrio

2011

Phil. Trans. R. Soc. A.

143

112

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“…Bewley [33] extended his earlier analysis of channel flow subject to blowing and suction at the wall and modified the above-mentioned conjecture. He showed that energetically (that is, considering the total power, accounting for both the power saved and the additional power for control input, for a given mass flux) the best one can do is to maintain a laminar flow.…”

Section: Limitation Of Control Performancementioning

confidence: 92%

Physics and control of wall turbulence for drag reduction

Kim

2011

Phil. Trans. R. Soc. A.

120

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Turbulence physics responsible for high skin-friction drag in turbulent boundary layers is first reviewed. A self-sustaining process of near-wall turbulence structures is then discussed from the perspective of controlling this process for the purpose of skin-friction drag reduction. After recognizing that key parts of this self-sustaining process are linear, a linear systems approach to boundary-layer control is discussed. It is shown that singular-value decomposition analysis of the linear system allows us to examine different approaches to boundary-layer control without carrying out the expensive nonlinear simulations. Results from the linear analysis are consistent with those observed in full nonlinear simulations, thus demonstrating the validity of the linear analysis. Finally, fundamental performance limit expected of optimal control input is discussed.

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“…A theoretical limit of the active friction drag reduction control, i.e. the relationship between drag reduction effect and input power, for control of a plane channel (Bewley, 2009) and of arbitrary ducts was discussed ). The existence of such a limit for the external flows, however, is still unclear.…”

Section: Introductionmentioning

confidence: 99%