Pressure fluctuation in high-Reynolds-number turbulent boundary layer: results from experiments and DNS

Tsuji, Yoshiyuki; Imayama, Shintaro; Schlatter, Philipp; Alfredsson, P. Henrik; Johansson, A.; Marušić, Ivan; Hutchins, Nicholas; Monty, Jason

doi:10.1080/14685248.2012.734625

Cited by 23 publications

(18 citation statements)

References 29 publications

(65 reference statements)

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“…Mean velocity and Reynolds stresses At x/l = −0.04, there is a narrow 'freestream' region, which is approximately 7 mm and 12 mm wide for Re θ (x 1 ) = 3360 and 5285, respectively, between the top and bottom wall boundary layers. However, following Tsuji et al (2012), due to the proximity between the top and bottom boundary layers, the pressure fluctuations in one might affect those in the other. Such effects are more consistent with channel flows.…”

Section: Results: Mean Flow and Turbulence Statisticsmentioning

confidence: 97%

Effect of mean and fluctuating pressure gradients on boundary layer turbulence

2014

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This study focuses on the effects of mean (favourable) and large-scale fluctuating pressure gradients on boundary layer turbulence. Two-dimensional (2D) particle image velocimetry (PIV) measurements, some of which are time-resolved, have been performed upstream of and within a sink flow for two inlet Reynolds numbers, Re θ (x 1 ) = 3360 and 5285. The corresponding acceleration parameters, K, are 1.3 × 10 −6 and 0.6 × 10 −6 . The time-resolved data at Re θ (x 1 ) = 3360 enables us to calculate the instantaneous pressure distributions by integrating the planar projection of the fluid material acceleration. As expected, all the locally normalized Reynolds stresses in the favourable pressure gradient (FPG) boundary layer are lower than those in the zero pressure gradient (ZPG) domain. However, the un-scaled stresses in the FPG region increase close to the wall and decay in the outer layer, indicating slow diffusion of near-wall turbulence into the outer region. Indeed, newly generated vortical structures remain confined to the near-wall region. An approximate analysis shows that this trend is caused by higher values of the streamwise and wall-normal gradients of mean streamwise velocity, combined with a slightly weaker strength of vortices in the FPG region. In both boundary layers, adverse pressure gradient fluctuations are mostly associated with sweeps, as the fluid approaching the wall decelerates. Conversely, FPG fluctuations are more likely to accompany ejections. In the ZPG boundary layer, loss of momentum near the wall during periods of strong large-scale adverse pressure gradient fluctuations and sweeps causes a phenomenon resembling local 3D flow separation. It is followed by a growing region of ejection. The flow deceleration before separation causes elevated near-wall small-scale turbulence, while high wall-normal momentum transfer occurs in the ejection region underneath the sweeps. In the FPG boundary layer, the instantaneous near-wall large-scale pressure gradient rarely becomes positive, as the pressure gradient fluctuations are weaker than the mean FPG. As a result, the separation-like phenomenon is markedly less pronounced and the sweeps do not show elevated small-scale turbulence and momentum transfer underneath them. In both boundary layers, periods of acceleration accompanying large-scale ejections involve near-wall spanwise contraction, and a high wall-normal momentum flux at all elevations. In the ZPG boundary layer, although some of the ejections are preceded, and presumably initiated, by regions of adverse pressure gradients and sweeps upstream, others are not. Conversely, in the FPG boundary layer, there is no evidence of sweeps or adverse pressure gradients immediately upstream of ejections. Apparently, the mechanisms initiating these ejections are either different from those involving large-scale sweeps or occur far upstream of the peak in FPG fluctuations.

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Section: Results: Mean Flow and Turbulence Statisticsmentioning

confidence: 97%

Effect of mean and fluctuating pressure gradients on boundary layer turbulence

2014

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“…The small spatial scales associated with turbulent flows impose severe sensor size limitations (Schewe 1983;Klewicki, Priyadarshana & Metzger 2008). The presence of significant background noise and structural vibration results in inherently noisy measurements that require careful correction (Tsuji et al 2007(Tsuji et al , 2012. Given these difficulties, our understanding of the wall-pressure field beneath turbulent flows lags behind our understanding of the fluctuating velocity fields.…”

Section: Introductionmentioning

confidence: 99%

On the structure and origin of pressure fluctuations in wall turbulence: predictions based on the resolvent analysis

2014

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We generate predictions for the fluctuating pressure field in turbulent pipe flow by reformulating the resolvent analysis of McKeon and Sharma (J. Fluid Mech., vol. 658, 2010, pp. 336-382) in terms of the so-called primitive variables. Under this analysis, the nonlinear convective terms in the Fourier-transformed Navier-Stokes equations (NSE) are treated as a forcing that is mapped to a velocity and pressure response by the resolvent of the linearized Navier-Stokes operator. At each wavenumber-frequency combination, the turbulent velocity and pressure field are represented by the most-amplified (rank-1) response modes, identified via a singular value decomposition of the resolvent. We show that these rank-1 response modes reconcile many of the key relationships among the velocity field, coherent structure (i.e. hairpin vortices), and the high-amplitude wall-pressure events observed in previous experiments and direct numerical simulations (DNS). A Green's function representation shows that the pressure fields obtained under this analysis correspond primarily to the fast pressure contribution arising from the linear interaction between the mean shear and the turbulent wall-normal velocity. Recovering the slow pressure requires an explicit treatment of the nonlinear interactions between the Fourier response modes. By considering the velocity and pressure fields associated with the triadically consistent mode combination studied by Sharma and McKeon (J. Fluid Mech., vol. 728, 2013, pp. 196-238), we identify the possibility of an apparent amplitude modulation effect in the pressure field, similar to that observed for the streamwise velocity field. However, unlike the streamwise velocity, for which the large scales of the flow are in phase with the envelope of the small-scale activity close to the wall, we expect there to be a π/2 phase difference between the large-scale wall-pressure and the envelope of the small-scale activity. Finally, we generate spectral predictions based on a rank-1 model assuming broadband forcing across all wavenumber-frequency combinations. Despite the significant simplifying assumptions, this approach reproduces trends observed in previous DNS for the wavenumber spectra of velocity and pressure, and for the scale-dependence of wall-pressure propagation speed.

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“…The detailed study of canonical incompressible wall-bounded flows, viz flat-plate zeropressure-gradient (ZPG) boundary-layer and internal fully developed (streamwise-invariant in the mean) flows (plane channel and pipe), has substantially advanced our understanding of wall turbulence (Smits, McKeon & Marusic 2011), although there is still debate on the differences in behaviour with increasing Reynolds number between boundary-layers and internal flows (Monty, Hutchins, Ng, Marusic & Chong 2009), especially concerning the scaling of the streamwise-velocity fluctuation u 2 near-wall peak (Hultmark, Bailey & Smits 2010) and of wall-pressure variance p 2 w (Tsuji, Imayama, Schlatter, Alfredsson, Johansson, Hutchins & Monty 2012). In regard with incompressible DNS studies, Schlatter &Örlü (2010) show that boundary-layer results are sensitive to inflow and boundary conditions used by different authors, contrary to fully developed internal flows which apply unambiguous streamwise-periodicity conditions.…”

Section: Introductionmentioning

confidence: 99%

Pressure, density, temperature and entropy fluctuations in compressible turbulent plane channel flow

Gerolymos

Vallet

2014

J. Fluid Mech.

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We investigate the fluctuations of thermodynamic state-variables in compressible aerodynamic wall-turbulence, using results of direct numerical simulation (DNS) of compressible turbulent plane channel flow. The basic transport equations governing the behaviour of thermodynamic variables (density, pressure, temperature and entropy) are reviewed and used to derive the exact transport equations for the variances and fluxes (transport by the fluctuating velocity field) of the thermodynamic fluctuations. The scaling with Reynolds and Mach number of compressible turbulent plane channel flow is discussed. Correlation coefficients and higher-order statistics of the thermodynamic fluctuations are examined. Finally, detailed budgets of the transport equations for the variances and fluxes of the thermodynamic variables from a well-resolved DNS are analysed. Implications of these results both to the understanding of the thermodynamic interactions in compressible wall-turbulence and to possible improvements in statistical modelling are assessed. Finally, the required extension of existing DNS data to fully characterise this canonical flow is discussed.

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Pressure fluctuation in high-Reynolds-number turbulent boundary layer: results from experiments and DNS

Cited by 23 publications

References 29 publications

Effect of mean and fluctuating pressure gradients on boundary layer turbulence

Effect of mean and fluctuating pressure gradients on boundary layer turbulence

On the structure and origin of pressure fluctuations in wall turbulence: predictions based on the resolvent analysis

Pressure, density, temperature and entropy fluctuations in compressible turbulent plane channel flow

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