Experimental and Computational Study of Turbulent Flows in a Channel With Two Pairs of Turbulence Promoters in Tandem

Liou, Tong‐Miin; Chang, Y.-Y.; Hwang, Donghyun

doi:10.1115/1.2909405

Cited by 68 publications

(16 citation statements)

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“…However at every location in the channel, the 0 / Nu Nu values decrease as Re increases. Liou et al [21] and Liou et al [22] showed a similar trend. Note that due to the evolution of the Dittus-Boelter Nusselt number, increasing with Re number, Nu values increase with the Reynolds number.…”

Section: Nu Nu =supporting

confidence: 63%

Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

Chanteloup

̈lcs

2002

Volume 1: 22nd Computers and Information in Engineering Conference

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A study of flow in two stationary models of two-pass internal coolant passages is presented, which focuses on the heat transfer characteristics in the two-pass coolant channel. Heat transfer measurements were made with a transient technique using thermochromic liquid crystal technique to measure a surface temperature. The technique allows full surface heat transfer coefficient measurements on all the walls. The coolant passage model consisted of two square passages, each having a 20 hydraulic diameter length, separated by a rounded-tip web of 0.2 passage widths, and connected by a sharp 180 deg bend with a rectangular outer wall. Ribs were mounted on the bottom and top walls of both legs, with a staggered arrangement, and at 45 deg to the flow. The rib height and spacing were 0.1 and 1.0 passage heights, respectively. The measurements were obtained for Reynolds numbers of 25000, 50000 and 70000. One geometry is equipped with extraction holes to simulate holes for film cooling. Two series of holes are placed solely in the bottom wall, 4 holes are located in the bend, and 12 in the downstream leg. The global extraction through the holes was set to 30%, 40% and 50% of the inlet massflow. This paper presents new measurements of the heat transfer in the straight legs, and in the bend of the passage. It shows the influence of Reynolds number and extraction on full surface measurements and area averaged results.

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Section: Nu Nu =supporting

confidence: 63%

Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

Chanteloup

̈lcs

2002

Volume 1: 22nd Computers and Information in Engineering Conference

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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 Regionsupporting

confidence: 50%

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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“…It is postulated that signi"cant interaction between the two obstacles can exist only if the #ow reaching the downstream one has not recovered fully its equilibrium condition. For the case of developed turbulent #ow, the typical length of the separated region behind a very thin obstacle is 8}12 times its height h, while recovery may well require an additional length of 10}15h (Bullock et al 1990;Scho"eld & Logan 1990;Liou et al 1990). These lengths can be compared to the experimental bounds obtained for l R /h and l K /h and shown in Table 1.…”

Section: A Model For the Behaviour Of The Systemmentioning

confidence: 98%

Aerodynamically Generated Acoustic Resonance in a Pipe With Annular Flow Restrictors

Stubos

Benocci

Palli

et al. 1999

Journal of Fluids and Structures

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Experimental and Computational Study of Turbulent Flows in a Channel With Two Pairs of Turbulence Promoters in Tandem

Cited by 68 publications

References 0 publications

Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

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

Aerodynamically Generated Acoustic Resonance in a Pipe With Annular Flow Restrictors

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