Coherent structures in oscillatory boundary layers

Costamagna, Paola; Vittori, Giovanna; Blondeaux, Paolo

doi:10.1017/s0022112002002665

Cited by 101 publications

(137 citation statements)

References 27 publications

(89 reference statements)

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“…Transition to turbulence has been investigated by direct numerical simulations of the Stokes boundary layer by Vittori & Verzicco (1998), Costamagna et al (2003) and Ozdemir et al (2014). Tuzi & Blondeaux (2008) have addressed the intermittent turbulent regime observed in a pulsating pipe.…”

Section: Literature Reviewmentioning

confidence: 99%

Linear and nonlinear dynamics of pulsatile channel flow

Pier

Schmid

2017

J. Fluid Mech.

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The dynamics of small-amplitude perturbations as well as the regime of fully developed nonlinear propagating waves is investigated for pulsatile channel flows. The timeperiodic base flows are known analytically and completely determined by the Reynolds number Re (based on the mean flowrate), the Womersley number Wo (a dimensionless expression of the frequency) and the flowrate waveform. This paper considers pulsatile flows with a single oscillating component and hence only three non-dimensional control parameters are present. Linear stability characteristics are obtained both by Floquet analyses and by linearized direct numerical simulations. In particular, the long-term growth or decay rates and the intracyclic modulation amplitudes are systematically computed. At large frequencies (mainly Wo 14), increasing the amplitude of the oscillating component is found to have a stabilizing effect, while it is destabilizing at lower frequencies; strongest destabilization is found for Wo ≃ 7. Whether stable or unstable, perturbations may undergo large-amplitude intracyclic modulations; these intracyclic modulation amplitudes reach huge values at low pulsation frequencies. For linearly unstable configurations, the resulting saturated fully developed finite-amplitude solutions are computed by direct numerical simulations of the complete Navier-Stokes equations. Essentially two types of nonlinear dynamics have been identified: "cruising" regimes for which nonlinearities are sustained throughout the entire pulsation cycle and which may be interpreted as modulated Tollmien-Schlichting waves, and "ballistic" regimes that are propelled into a nonlinear phase before subsiding again to small amplitudes within every pulsation cycle. Cruising regimes are found to prevail for weak baseflow pulsation amplitudes, while ballistic regimes are selected at larger pulsation amplitudes; at larger pulsation frequencies, however, the ballistic regime may be bypassed due to the stabilizing effect of the base-flow pulsating component. By investigating extended regions of a multi-dimensional parameter space and considering both two-dimensional and threedimensional perturbations, the linear and nonlinear dynamics are systematically explored and characterized.

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Section: Literature Reviewmentioning

confidence: 99%

Linear and nonlinear dynamics of pulsatile channel flow

Pier

Schmid

2017

J. Fluid Mech.

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“…As in Blondeaux and Vittori (1994), Costamagna et al (2003) and Mazzuoli et al (2011), the bottom profile has a small waviness in the 1 * -and 3 * -directions, and the vertical coordinate…”

Section: Numerical Modelmentioning

confidence: 98%

“…The method uses second order finite difference approximations for the spatial derivatives and the fractionstep method for the time derivatives in the Navier-Stokes equation. For a more detailed description of the numerical procedure, see Kim and Moin (1985), Orlandi (1989), Vittori and Verzicco (1998) and Costamagna et al (2003). The test conditions and the properties of the numerical mesh are given in Table 1.…”

Section: Numerical Modelmentioning

confidence: 99%

Role of Vertical Pressure Gradient in Wave Boundary Layers

Jensen

Sumer

Vittori

et al. 2014

Int. Conf. Coastal. Eng.

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The pressure field in an oscillatory boundary layer is obtained by means of direct numerical simulations (DNS). The vertical pressure gradient is treated as any other turbulence quantity and its statistical properties are calculated from the DNS data. Moreover, a criterion involving the vertical pressure gradient is used to detect spots. The large fluctuations of the vertical pressure gradient, which take place in the turbulent flow, have significant implications for sediment transport. Keywords: wave boundary layers, turbulence, vertical pressure gradient, DNS, transition to turbulence INTRODUCTIONWave boundary layers have been studied extensively over the past decades. The studies cover the entire range of flow regimes: laminar, transitional and turbulent regimes. Observations show that, in the transitional regime, turbulence first emerges in isolated areas where the flow "bursts" with violent oscillations . These areas, which are called "turbulent spots", and they grow in time, and once they merge, the flow becomes fully turbulent. Carstensen et al's. (2010) work was later extended to the case of solitary wave boundary layers and wave boundary layers over a rough bed (Carstensen, Sumer and Fredsøe, 2012). Mazzuoli, Vittori and Blondeaux (2011)

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“…Most previous researchers have mainly studied boundary layers under sinusoidal waves [7,8,11,12]. However, in shallow water circumstance of coastal areas, the wave profiles are generally asymmetric due to nonlinearity.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of boundary layer flow under cnoidal waves

Chen

Zhou

et al. 2015

Acta Mech. Sin.

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Water waves in coastal areas are generally nonlinear, exhibiting asymmetric velocity profiles with different amplitudes of crest and trough. The behaviors of the boundary layer under asymmetric waves are of great significance for sediment transport in natural circumstances. While previous studies have mainly focused on linear or symmetric waves, asymmetric wave-induced flows remain unclear, particularly in the flow regime with high Reynolds numbers. Taking cnoidal wave as a typical example of asymmetric waves, we propose to use an infinite immersed plate oscillating cnoidally in its own plane in quiescent water to simulate asymmetric wave boundary layer. A large eddy simulation approach with Smagorinsky subgrid model is adopted to investigate the flow characteristics of the boundary layer. It is verified that the model well reproduces experimental and theoretical results. Then a series of numerical experiments are carried out to study the boundary layer beneath cnoidal waves from laminar to fully developed turbulent regimes at high Reynolds numbers, larger than ever studied before. Results of velocity profile, wall shear stress, friction coefficient, phase lead between velocity and wall shear stress, and the boundary layer thickness are obtained. The dependencies of these boundary layer properties on the asymmetric degree and Reynolds number are discussed in detail.

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Coherent structures in oscillatory boundary layers

Cited by 101 publications

References 27 publications

Linear and nonlinear dynamics of pulsatile channel flow

Linear and nonlinear dynamics of pulsatile channel flow

Role of Vertical Pressure Gradient in Wave Boundary Layers

Large eddy simulation of boundary layer flow under cnoidal waves

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