Velocity scales in the near-wall layer beneath reattaching turbulent separated and boundary layer flows

Hancock, P. E.

doi:10.1016/j.euromechflu.2004.10.003

Cited by 3 publications

(3 citation statements)

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“…The vertical velocity v could not be measured below y = 5 mm. Velocity gradient effects are only significant near the surface, when u τ y/ν is 10 or less (Hancock 2005), and are not relevant to the results presented here.…”

Section: Flow Rig and Measurements Techniquesmentioning

confidence: 68%

“…Based on the height s of the wires above the surface (nominally 0.05 mm) the non-dimensional height of the wires su τ /ν did not exceed 0.7. As discussed by Hancock (2005Hancock ( , 2007, the viscous sublayer for the fluctuations is not linear, even at this small distance. Nevertheless, the error in τ will not have exceeded 10 %, at most.…”

Section: Flow Rig and Measurements Techniquesmentioning

confidence: 81%

“…Further analysis of the near-wall layer, and in particular the Reynolds stresses and higher order moments, is given by Hancock (2005Hancock ( , 2007. Those papers explore the idea that each Reynolds stress has its own velocity scale.…”

Section: Introductionmentioning

confidence: 99%

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Moderately three-dimensional separated and reattaching turbulent flow

Hardman

Hancock

2010

J. Fluid Mech.

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A fully three-dimensional turbulent separated flow was set up such that it had a systematic link to two-dimensional flow, as a way of investigating the more complicated nature of this flow type. The central region of the flow was fully three-dimensional, but was bounded on its sides by regions of ‘spanwise invariance’ in which the flow was invariant in the lateral direction, or very nearly so. A special case of spanwise invariance, which is statistically two-dimensional, is one in which the streamlines are also coplanar, or at least nominally so in numerous experimental studies. Another aspect of the present arrangement is that the side regions should ideally provide well-defined boundary conditions. The separation was formed downstream of a doubly swept normal flat plate, forming a ‘v’-shaped separation line, mounted on the front of a splitter plate, mounted in the centre of the wind tunnel working section. The predominantly inward flow to the central region implies a negative lateral strain rate (∂W/∂z), but all nine strain rates are non-zero. Measurements were made using pulsed-wire anemometry techniques for mean velocities, Reynolds stresses and wall shear stress. Even though the sweep angle is mild at ±10°, the effect is to increase the bubble height by over 50% in its centre to create a ‘bulge’, symmetrical about the centreline. The degree of three-dimensionality is described as moderate in that the peak inflow velocity from the side regions is less than 0.2 of the free-stream velocity, but comparable with the peak in the reverse-flow velocity. A larger sweep angle would give a larger inflow velocity. A separate study (Cao & Hancock, Eur. J. Mech. B/Fluids, vol. 23, 2004, p. 519) has shown that the bulge persists very far downstream, so that accurate physical modelling of the separated region is likely to be important in modelling the flow well downstream. An intermediate region exists between the invariant side region and the bulge, where all the stress levels are reduced, as would be expected from the effects of streamline convergence. Although overall there is a flow inward to the centre (streamline convergence), part of the overlying shear layer is subjected to diverging flow and an intensification of Reynolds stresses near the centre of the bulge.

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Section: Flow Rig and Measurements Techniquesmentioning

confidence: 68%

Section: Flow Rig and Measurements Techniquesmentioning

confidence: 81%