THE NEAR-WALL STRUCTURES OF TURBULENT WALL FLOWS

2006 ◽  
pp. 53-70 ◽  
Author(s):  
Javier Jiménez ◽  
Genta Kawahara ◽  
Mark P. Simens ◽  
Juan C. del Álamo
Keyword(s):  
Wall Flows ◽  
Wall Structures ◽  
Turbulent Wall ◽  
Near Wall

Statistical properties of streamline geometry in turbulent wall-flows

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Rina Perven ◽  
Jimmy Philip ◽  
Joseph Klewicki
Keyword(s):  
Statistical Properties ◽  
Wall Flows ◽  
Turbulent Wall

On the near-wall structures and statistics of fluctuating pressure in compressible turbulent channel flows

2020 ◽  
Vol 32 (11) ◽  
pp. 115121 ◽  
Author(s):  
Jiupeng Tang ◽  
Zhiye Zhao ◽  
Zhen-Hua Wan ◽  
Nan-Sheng Liu
Keyword(s):  
Channel Flows ◽  
Fluctuating Pressure ◽  
Turbulent Channel Flows ◽  
Wall Structures ◽  
Near Wall

Law of bounded dissipation and its consequences in turbulent wall flows

2021 ◽  
Vol 933 ◽  
Author(s):  
Xi Chen ◽  
Katepalli R. Sreenivasan
Keyword(s):  
Dissipation Rate ◽  
Scaling Law ◽  
Random Variable ◽  
Energy Dissipation Rate ◽  
Shear Stresses ◽  
Mean Velocity ◽  
Wall Flows ◽  
Maximum Value ◽  
Turbulent Wall ◽  
Promising Perspective

The dominant paradigm in turbulent wall flows is that the mean velocity near the wall, when scaled on wall variables, is independent of the friction Reynolds number $Re_\tau$ . This paradigm faces challenges when applied to fluctuations but has received serious attention only recently. Here, by extending our earlier work (Chen & Sreenivasan, J. Fluid Mech., vol. 908, 2021, p. R3) we present a promising perspective, and support it with data, that fluctuations displaying non-zero wall values, or near-wall peaks, are bounded for large values of $Re_\tau$ , owing to the natural constraint that the dissipation rate is bounded. Specifically, $\varPhi _\infty - \varPhi = C_\varPhi \,Re_\tau ^{-1/4},$ where $\varPhi$ represents the maximum value of any of the following quantities: energy dissipation rate, turbulent diffusion, fluctuations of pressure, streamwise and spanwise velocities, squares of vorticity components, and the wall values of pressure and shear stresses; the subscript $\infty$ denotes the bounded asymptotic value of $\varPhi$ , and the coefficient $C_\varPhi$ depends on $\varPhi$ but not on $Re_\tau$ . Moreover, there exists a scaling law for the maximum value in the wall-normal direction of high-order moments, of the form $\langle \varphi ^{2q}\rangle ^{{1}/{q}}_{max}= \alpha _q-\beta _q\,Re^{-1/4}_\tau$ , where $\varphi$ represents the streamwise or spanwise velocity fluctuation, and $\alpha _q$ and $\beta _q$ are independent of $Re_\tau$ . Excellent agreement with available data is observed. A stochastic process for which the random variable has the form just mentioned, referred to here as the ‘linear $q$ -norm Gaussian’, is proposed to explain the observed linear dependence of $\alpha _q$ on $q$ .

Similarity of undeveloped turbulent near-wall flows

1979 ◽  
Vol 37 (6) ◽  
pp. 1415-1418
Author(s):  
V. A. Gorodtsov
Keyword(s):  
Wall Flows ◽  
Near Wall

Near-Wall Modeling of Plane Turbulent Wall Jets

1997 ◽  
Vol 119 (2) ◽  
pp. 304-313 ◽  
Author(s):  
G. Gerodimos ◽  
R. M. C. So
Keyword(s):  
Boundary Layer ◽  
Outer Region ◽  
Plane Wall ◽  
Equation Modeling ◽  
Wall Jets ◽  
Free Jet ◽  
Turbulent Wall Jets ◽  
Turbulent Wall ◽  
Simple Flows ◽  
Near Wall

In most two-dimensional simple turbulent flows, the location of zero shear usually coincides with that of vanishing mean velocity gradient. However, such is not the case for plane turbulent wall jets. This could be due to the fact that the driving potential is the jet exit momentum, which gives rise to an outer region that resembles a free jet and an inner layer that is similar to a boundary layer. The interaction of a free-jet like flow with a boundary-layer type flow distinguishes the plane wall jet from other simple flows. Consequently, in the past, two-equation turbulence models are seldom able to predict the jet spread correctly. The present study investigates the appropriateness of two-equation modeling; particularly the importance of near-wall modeling and the validity of the equilibrium turbulence assumption. An improved near-wall model and three others are analyzed and their predictions are compared with recent measurements of plane wall jets. The jet spread is calculated correctly by the improved model, which is able to replicate the mixing behavior between the outer jet-like and inner wall layer and is asymptotically consistent. Good agreement with other measured quantities is also obtained. However, other near-wall models tested are also capable of reproducing the Reynolds-number effects of plane wall jets, but their predictions of the jet spread are incorrect.

Evolution and dynamics of shear-layer structures in near-wall turbulence

1991 ◽  
Vol 224 ◽  
pp. 579-599 ◽  
Author(s):  
Arne V. Johansson ◽  
P. Henrik Alfredsson ◽  
John Kim
Keyword(s):  
Turbulent Channel Flow ◽  
Wall Turbulence ◽  
Turbulent Shear ◽  
Spanwise Direction ◽  
Wall Structures ◽  
Layer Structures ◽  
Turbulence Production ◽  
Near Wall Turbulence ◽  
Probe Measurements ◽  
Near Wall

Near-wall flow structures in turbulent shear flows are analysed, with particular emphasis on the study of their space–time evolution and connection to turbulence production. The results are obtained from investigation of a database generated from direct numerical simulation of turbulent channel flow at a Reynolds number of 180 based on half-channel width and friction velocity. New light is shed on problems associated with conditional sampling techniques, together with methods to improve these techniques, for use both in physical and numerical experiments. The results clearly indicate that earlier conceptual models of the processes associated with near-wall turbulence production, based on flow visualization and probe measurements need to be modified. For instance, the development of asymmetry in the spanwise direction seems to be an important element in the evolution of near-wall structures in general, and for shear layers in particular. The inhibition of spanwise motion of the near-wall streaky pattern may be the primary reason for the ability of small longitudinal riblets to reduce turbulent skin friction below the value for a flat surface.

On the nature of the organized structures in turbulent near-wall flows

1997 ◽  
Vol 32 (1) ◽  
pp. 18-23 ◽  
Author(s):  
N. B. Nikitin ◽  
S. I. Chernyshenko
Keyword(s):  
Wall Flows ◽  
Near Wall
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