LDA measurements in a turbulent boundary layer over a d-type rough wall

Djenidi, L.; Antonia, R. A.; Anselmet, Fabien

doi:10.1007/bf00195431

Cited by 34 publications

(20 citation statements)

References 20 publications

(17 reference statements)

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“…Djenidi et al 1994Djenidi et al , 1999. In both situations, irregular ejections of cavity fluid take place and the process appears to be sequential from upstream to downstream (Table 2).…”

Section: Discussionmentioning

confidence: 99%

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Air–water flows down stepped chutes: turbulence and flow structure observations

Chanson

Toombes

2002

International Journal of Multiphase Flow

207

179

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: Interactions between turbulent waters and atmosphere may lead to strong air-water mixing.This experimental study is focused on the flow down a staircase channel characterised by very strong flow aeration and turbulence. Interfacial aeration is characterised by strong air-water mixing extending down to the invert. The size of entrained bubbles and droplets extends over several orders of magnitude, and a significant number of bubble/droplet clusters was observed. Velocity and turbulence intensity measurements suggest high levels of turbulence across the entire air-water flow. The increase in turbulence levels, compared to single-phase flow situations, is proportional to the number of entrained particles.

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“…Djenidi et al 1994Djenidi et al , 1999. In both situations, irregular ejections of cavity fluid take place and the process appears to be sequential from upstream to downstream (Table 2).…”

Section: Discussionmentioning

confidence: 99%

“…Page 25 Djenidi et al (1994) 0. δ * : displacement thickness; δ M : momentum thickness; ∆t : ejection duration. .…”

Section: List Of Symbolsmentioning

confidence: 99%

Air–water flows down stepped chutes: turbulence and flow structure observations

Chanson

Toombes

2002

International Journal of Multiphase Flow

207

179

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“…The recirculation motion within the step cavities is three dimensional (MATOS et al 2000, MATOS 2001, GONZALEZ and CHANSON 2008. Some random cavity ejections between the step cavity and the main stream skimming Other studies detailed the momentum exchange and cavity ejection processes (DJENIDI et al 1994,1999, TANTIRIGE et al 1994). …”

Section: Air-water Flow Properties In Step Cavity Presentationmentioning

confidence: 99%

Air–water flow properties in step cavity down a stepped chute

Felder

Chanson

2011

International Journal of Multiphase Flow

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For the last three decades, the research into skimming flows down stepped chutes was driven by needs for better design guidelines. The skimming flow is characterised by some momentum transfer from the main stream to the recirculation zones in the shear layer developing downstream of each step edge. In the present study some physical modelling was conducted in a relatively large facility and detailed air-water flow measurements were conducted at several locations along a triangular cavity. The data implied some self-similarity of the main flow properties in the upper flow region, at step edges as well as at all locations along the step cavity. In the developing shear layer and cavity region (i.e. y/h < 0.3), the air-water flow properties presented some specific features highlighting the development of the mixing layer downstream of the step edge and the strong interactions between cavity recirculation and mainstream skimming flows. Both void fraction and bubble count rate data showed a local maximum in the developing shear layer, although the local maximum void fraction was always located below the local maximum bubble count rate. The velocity profiles had the same shape as the classical monophase flow data. The air-water flow properties highlighted some intense turbulence in the mixing layer that would be associated with large shear stresses and bubbleturbulence interactions.

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“…The structures generated in this manner had length scales proportional to the roughness height "k" and were found to blend into the outer flow farther away from the roughness. Subsequent flow visualization studies of individual grooves by Liou et al (1990) and Djenidi et al (1994) provide additional evidence supporting these observations. The rough-wall study of Grass (1971) in a free-surface channel flow using hydrogen bubbles clearly identified the differences of near-wall ejection and inrush (sweep) events between smooth and rough walls (sand and rounded pebbles).…”

Section: Roughness Effects In the Near-wall Regionmentioning

confidence: 63%

Studies of Real Roughness Effects for Improved Modeling and Control of Practical Wall-Bounded Turbulent Flows

Christensen¹,

Wu²

2008

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The public reporting burden for this collection of information is estimated to average 1 hour per response. including the time for reviewing instructions, sea"hing existing data soUrces, gathering and maintaining the data needed, and completing and reviewving the collection of infomation. Send comments regaliong this burden estimate or any otiler aspect of tts collection of information. including suggestions for reducing fhe burden, to the Department of Defense, Executive Service Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law. no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a curently valid OMB control number. PLEASE DO NOT RETURN YOUR A F R L S R SUPPLEMENTARY NOTES ABSTRACTThe present effort investigates the effects of practical roughness replicated from a turbine blade damaged by deposition of foreign material. statistical and structural characteristics of wall turbulence. Two-dimensional particle image velocimetry (PIV) measurements are performed in the streamwise-wall-normal plane of turbulent boundary layers at momentum Reynolds numbers of 8000 and 13000. The surface conditions include a smooth wall and two highly-irregular rough walls. These rough surfaces have the same roughness topography but differ in spatial scaling. The validity of Townsend's wall similarity hypothesis in the presence of practical roughness is assessed and the impact of this roughness on the spatial structure of the flow is investigated. In addition, stereoscopic PIV measurements are made in streamwise-spanwise planes of smooth-and rough-wall turbulent boundary layers both within and at the outer edge of the roughness sublayer. This data is used to explore the impact of dominant topographical features on the near-wall flow as well as the influence of practical roughness on the spatial organization of the flow.Understanding such effects provides a stepping stone toward efficient modeling and control of practical flows in the presence of roughness. SUBJECT TERMS

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LDA measurements in a turbulent boundary layer over a d-type rough wall

Cited by 34 publications

References 20 publications

Air–water flows down stepped chutes: turbulence and flow structure observations

Air–water flows down stepped chutes: turbulence and flow structure observations

Air–water flow properties in step cavity down a stepped chute

Studies of Real Roughness Effects for Improved Modeling and Control of Practical Wall-Bounded Turbulent Flows

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