Sustained sub-laminar drag in a fully developed channel flow

Min, Taegee; Kang, Sung Ha; Speyer, Jason L.; Kim, John

doi:10.1017/s0022112006000206

Cited by 132 publications

(177 citation statements)

References 10 publications

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“…Bechert et al 1997;Xu, Rempfer & Lumley 2003;Fukagata et al 2008;Choi et al 2012), open-loop active control (transverse wall oscillations, upstream-travelling waves of blowing and suction, streamwise waves of spanwise velocity at the wall (see e.g. Quadrio & Ricco 2004;Min et al 2006;Quadrio, Ricco & Viotti 2009;Moarref & Jovanovic 2012)), as well as feedback flow control.…”

Section: Introductionmentioning

confidence: 99%

Opposition control within the resolvent analysis framework

2014

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as an example. Under this formulation, the velocity field for turbulent pipe flow is decomposed into a series of highly amplified (rank-1) response modes, identified from a gain analysis of the Fourier-transformed NavierStokes equations. These rank-1 velocity responses represent propagating structures of given streamwise/spanwise wavelength and temporal frequency, whose wall-normal footprint depends on the phase speed of the mode. Opposition control, introduced via the boundary condition on wall-normal velocity, affects the amplification characteristics (and wall-normal structure) of these response modes; a decrease in gain indicates mode suppression, which leads to a decrease in the drag contribution from that mode. With basic assumptions, this rank-1 model reproduces trends observed in previous direct numerical simulation and large eddy simulation, without requiring high-performance computing facilities. Further, a wavenumber-frequency breakdown of control explains the deterioration of opposition control performance with increasing sensor elevation and Reynolds number. It is shown that slower-moving modes localized near the wall (i.e. attached modes) are suppressed by opposition control. Faster-moving detached modes, which are more energetic at higher Reynolds number and more likely to be detected by sensors far from the wall, are further amplified. These faster-moving modes require a phase lag between sensor and actuator velocity for suppression. Thus, the effectiveness of opposition control is determined by a trade-off between the modes detected by the sensor. However, it may be possible to develop control strategies optimized for individual modes. A brief exploration of such mode-optimized control suggests the potential for significant performance improvement.

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Section: Introductionmentioning

confidence: 99%

Opposition control within the resolvent analysis framework

2014

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“…Hence, in practice most flows are turbulent at sufficiently large Re. While the stability of laminar flow has been studied in great detail, little attention has been paid to the susceptibility of turbulence, the general assumption being that once turbulence is established it is stable.Many turbulence control strategies have been put forward to reduce the drag encountered in shear flows [7][8][9][10][11][12][13][14][15][16][17] . Recent strategies employ feedback mechanisms to actively counter selected velocity components or vortices.…”

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confidence: 99%

Destabilizing turbulence in pipe flow

et al. 2018

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Turbulence is the major cause of friction losses in transport processes and it is responsible for a drastic drag increase in flows over bounding surfaces. While much effort is invested into developing ways to control and reduce turbulence intensities [1][2][3] , so far no methods exist to altogether eliminate turbulence if velocities are sufficiently large. We demonstrate for pipe flow that appropriate distortions to the velocity profile lead to a complete collapse of turbulence and subsequently friction losses are reduced by as much as 90%. Counterintuitively, the return to laminar motion is accomplished by initially increasing turbulence intensities or by transiently amplifying wall shear. Since neither the Reynolds number nor the shear stresses decrease (the latter often increase), these measures are not indicative of turbulence collapse. Instead, an amplification mechanism 4,5 measuring the interaction between eddies and the mean shear is found to set a threshold below which turbulence is suppressed beyond recovery.Flows through pipes and hydraulic networks are generally turbulent and the friction losses encountered in these flows are responsible for approximately 10% of the global electric energy consumption. Here turbulence causes a severe drag increase and consequently much larger forces are needed to maintain desired flow rates. In pipes, both laminar and turbulent states are stable (the former is believed to be linearly stable for all Reynolds number (Re) values; the latter is stable if Re > 2, 040 (ref. 6 )), but with increasing speed the laminar state becomes more and more susceptible to small disturbances. Hence, in practice most flows are turbulent at sufficiently large Re. While the stability of laminar flow has been studied in great detail, little attention has been paid to the susceptibility of turbulence, the general assumption being that once turbulence is established it is stable.Many turbulence control strategies have been put forward to reduce the drag encountered in shear flows [7][8][9][10][11][12][13][14][15][16][17] . Recent strategies employ feedback mechanisms to actively counter selected velocity components or vortices. Such methods usually require knowledge of the full turbulent velocity field. In computer simulations 7,8 , it could be demonstrated that under these ideal conditions, flows at a low Re number can even be relaminarized. In experiments, the required detailed manipulation of the time-dependent velocity field is, however, currently impossible to achieve. Other studies employ passive (for example, riblets) or active (oscillations or excitation of travelling waves) methods to interfere with the near-wall turbulence creation. Typically here drag reduction of 10 to 40% has been reported, but often the control cost is substantially higher than the gain, or a net gain can be achieved only in a narrow Re number regime.Instead of attempting to control or counter certain components of the complex fluctuating flow fields, we will show in the following that by appropriately dist...

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“…Apart from these attempts using feedback control, Higashi et al (2011) reported that such a dissimilar control effect can also be attained by an open-loop control, i.e., a traveling wave-like blowing and suction (Min et al, 2006;Lieu et al, 2010;Mamori et al, 2014), when the boundary conditions for velocity and temperature are dissimilar (i.e., the constant temperature difference condition). They performed a laminar analysis and DNS of a turbulent channel flow and concluded that the similarity is broken by the phase difference between the velocity and the temperature due to a viscous phase shift in the region near the walls.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer in fully developed turbulent channel flow with streamwise traveling wave-like wall deformation

Uchino¹,

Mamori

Fukagata³

2017

JTST

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The dissimilarity between the momentum and heat transfer due to streamwise traveling wave-like wall deformation in turbulent channel flows is investigated through direct numerical simulations. The flow rate is kept constant, and the bulk Reynolds number is Re b = 5600. A constant temperature difference condition is imposed on the channel walls. The parametric study shows that the heat transfer is enhanced when the wave travels in the upstream direction. The maximum analogy factor is found to be 1.13, i.e., 13% enhancement of heat transfer under a given pressure gradient, when the wall deformation amplitude is large and the wall deformation period is short. An analysis using the identity equations for the drag and the heat transfer with a three component decomposition reveals that the random component plays an important role in the enhancement of the heat transfer.

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Sustained sub-laminar drag in a fully developed channel flow

Cited by 132 publications

References 10 publications

Opposition control within the resolvent analysis framework

Opposition control within the resolvent analysis framework

Destabilizing turbulence in pipe flow

Heat transfer in fully developed turbulent channel flow with streamwise traveling wave-like wall deformation

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