Figure 1.
Low-speed streaks (from Kline et al. 1967). Flow is from top to bottom.
Figure 2.
Instantaneous velocity profiles (from Grass 1971).
Figure 3.
Suggested horseshoe vortex model of wall-bounded turbulence (from Theodorsen 1952).
Figure 4.
Boundary layer structure at Re? = 7500 (adapted from Head and Bandyopadhyay 1981). Flow is from right to left.
Figure 5.
Inclined features being convected past light plane at, (a) 45° upstream, and (b) 45° downstream, (from Head and Bandyopadhyay 1981).
Figure 6.
Views with transverse light plane at 45° upstream and downstream. From top: Re? = 600, Re? = 1700 and Re? = 9400, (adapted from Head and Bandyopadhyay).
Figure 7.
Geometry of horseshoe/hairpin vortices (from Robinson after Head and Bandyopadhyay 1981).
Figure 8.
Dual view of a dye-marked single hairpin vortex, (from Haidari and Smith 1994).
Figure 9.
Iso-surfaces of the second invariant of the velocity gradient tensor (from Wu and Moin 2009). The iso-surfaces are coloured based on local values of U with higher U represented by red
Figure 10.
Isosurface of the discriminant of the velocity gradient tensor from the simulation of Jimenez et al. 2010. The flow is from left to right, and the wall-parallel dimensions of the box are approximately 18 × 9 times the boundary-layer thickness at the centre of the box, spanning Re? = 1420 - 1900. The isosurface is coloured by the distance to the wall, from y/d ˜ 0.3 - 0.4 for the deepest blue, to y ˜ d for the brightest red.
Figure 11.
Structure of an average model of vortex line near the wall (from Willmarth and Tu 1967).
Figure 12.
Generation of ring vortices by instability in actual shear layer (from Black 1968).
Figure 13.
Intermittency explained by random variation in strength of consecutive vortex systems (from Black 1968).
Figure 14.
Conceptual model of the turbulence near the wall during a "cyclic? process (from Hinze 1979)
Figure 15.
Illustration of the breakdown and formation of hairpin vortices during a streakbursting process. Low-speed streak regions indicated by shading (from Smith 1984). Flow is from left to right.
Figure 16.
Parent vortex showing where new streamwise and spanwise offspring are likely to arise, (from Bernard and Wallace 2002). Flow is in positive x direction.
Figure 17.
Conceptual model of quasi-streamwise vortex structure; A is the parent of B, which is the parent of C, (from Miyake et al. 1997).
Figure 18.
?-vortex configuration (from Perry and Chong 1982).
Figure 19.
Schematic of carpet of vorticity being wrapped into eddy, (from Perry and Chong 1982).
Figure 20.
Conceptual scenario of nested packets of hairpins aligned coherently in the streamwise direction (from Adrian et al. 2000).
Figure 21.
Instantaneous velocity realizations in turbulent channel fl ow at Ret = 547, with a constant convection velocity removed, (from Christensen and Adrian 2000). Flow is from left to right.
Figure 22.
Linear stochastic estimations of the conditionally average velocity fi eld in channel fl ow at Ret = 547, (from Christensen and Adrian 2001). Flow is from left to right.
Figure 23.
Direction fi eld from linear stochastic estimation of velocity based on positive signed swirl (swirl consistent with mean vorticity) at Zref / d = 0.19. (from Hambleton et al. 2006). The vertical plane is shown in (a), with the condition point marked with a cross, and the horizontal plane is shown in (b). Note that y and z are used for spanwise and wall-normal coordinates respectively (the opposite convention to this review). Flow is from left to right.
Figure 24.
The hairpin vortex packet produced by the simulations of Zhou et al. 1999. Flow is in positive x direction.
Figure 25.
The hairpin vortex packet produced by the simulations of Adrian and Liu et al. (2002) that include 5% noise, taken from Adrian 2007. Flow is in positive x direction.
Figure 26.
Visualisation of a hairpin vortex packet with high- and low-speed structures (from Dennis and Nickels 2011). Black iso-surface: |?ci|iso| = 0.18|?ci|max. Blue iso-surface: uiso = 0.1U. Red iso-surface: uiso = 0.1U. Flow is in positive x direction.
Figure 27.
Conditionally averaged swirling fields given spanwise swirl showing the variation in average vortex with distance from the wall (from Dennis and Nickels 2011a). Condition is for ?ciz > 0.18?ciz,max, iso-surfaces shown are for ?ci,iso = 0.08?ci,max
Figure 28.
Three-dimensional plot of the average velocity fi eld conditioned to the tall attached clusters (taken from del Alamo et al. 2006). The black mesh is an isosurface of the p.d.f. of the vortex positions and contains 57% of the data. The blue volume surrounding the cluster is the isosurface u+ = 0.3. The red volume downstream of the cluster is the isosurface u+ = 0.1. The green volumes indicate the vortices (based on the discriminant criterion). Flow is in positive rx direction.
Figure 29.
Smoke visualization of the wall-region (0 < x / d = < 0.01, 0 < y / d < 0.015) of the atmospheric boundary layer at Re? = 9 × 106 (from Hommema and Adrian 2003). Flow is from left to right.
Figure 30.
(a) Example rake signal at z / d = 0.15, for Re¿ = 14380, and (b) PIV snapshot (from Hutchins & Marusic 2007a.) Note that y and z are used for spanwise and wall-normal coordinates respectively (the opposite convention to this review). Flow is from left to right
Figure 31.
Top-down view of very large-scale motion draped with vortices (Dennis and Nickels 2011a). Black iso-surface: |?ciz|iso = 0.18 |?ci|max. Blue iso-surface: uiso = - 0.1U. Red iso-surface: uiso = 0.1U. Flow is from left to right.
Figure 32.
The two most energetic POD modes displaying roll-cell-like behaviour. The right iso-surfaces indicate the swirling patterns of u (at one-half of maximum magnitude), while the left plots display the colour u fl uctuation and in-plane velocity vectors (Baltzer et al. 2013). Flow is in positive x direction.
Figure 33.
Model prediction of the swirl fi eld (50% of maximum) and streamwise velocity (±50% of maximum) arising for a particular mode combination (from Sharma and McKeon 2013). Isosurfaces of swirl are black and isosurfaces of streamwise velocity fl uctuation are red and blue for high and low momentum, respectively. Flow is in positive x direction.
