Measurements of the Turbulent Transport of Heat and Momentum in Convexly Curved Boundary Layers: Effects of Curvature, Recovery and Free-Stream Turbulence

Kim, J.; Simon, Terrence W.

doi:10.1115/1.3262171

Cited by 12 publications

(5 citation statements)

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“…Bend ows have been extensively studied experimentally (Al- Rafai et al, 1990;Cheng and Farokhi, 1992; Kim and Simon, 1988), and numerically (Jayanti et al, 1990;R utten et al, 2001;Van de Vosse et al, 1989;Wang and Shirazi, 2001;Bergstrom et al, 1998). It is well known that the ow in bends is a ected by the wall curvature, which acts on the main features of the resulting ow, like mean velocity proÿles, wall pressure and turbulent characteristics (Sudo et al, 1998;Cheng and Farokhi, 1992).…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of bend and torus flows, part I : effect of swirl motion on flow structure in U-bend

Pruvost

Legrand

Legentilhomme

2004

Chemical Engineering Science

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As a preliminary study to ow modeling in torus reactors, simulations are carried out in well-known standard geometries, namely 90 • and 180 • bends. For the latter, two ow conÿgurations are considered, with and without initial swirl motion so as to approach torus reactor conditions. E ciency of the commercial CFD code FLUENT is investigated by comparing predicted results with experimental measurements available in the literature for both bended conÿgurations. Di erent turbulent models and near-wall considerations are considered, including k -and high Reynolds-stresses models, with the standard wall-function approach as well as the two-layer zonal model and low-Re k -models.After validation of the numerical strategy, a parametric study is made to better understand the interactions between Dean vortices, involved by the bend curvature, and the main rotating motion generated by the swirl motion. Simulations are achieved for various values of the initial swirl intensity applied at the bend entry. Numerical simulations show di erent ow structures, resulting from the progressive Dean vortices perturbations with the increase of swirl intensity. ?

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Section: Introductionmentioning

confidence: 99%

Numerical investigation of bend and torus flows, part I : effect of swirl motion on flow structure in U-bend

Pruvost

Legrand

Legentilhomme

2004

Chemical Engineering Science

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“…In You et al [1986], recovery data was also measured for the weak-to-intermediate curvatures (0.01-0.05). The effects of curvature and recovery on the turbulent transport quantities were reported by Kim and Simon [1987] using mild strength of curvature (/R 0.03).…”

Section: Figurementioning

confidence: 99%

Convex Curvature Effect on the WakeIncluding Recovery from the Curvature

You

1995

International Journal of Rotating Machinery

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Streamwise convex-curvature effect including recovery process is discussed. Previous studies have demonstrated that even mild streamwise curvature has a marked effect on turbulence structure, heat transfer and skin friction coefficient. This effect is further investigated in the present study with Coles wake law. Coles previously reported that flows in or near equilibrium have a constant wake parameter depending on the strength of streamwise pressure gradient. Turbulent boundary layers on the curved and following recovery wall may not be in or near equilibrium and the wake parameter may depend upon the strength of curvature, /R. Different streamwise curvature strength, ranging 0.01-0.1, is tested to confirm the validity of the wake law. The ratio of wake parameter between the curved and flat wall is found to be proportional to that of skin friction coefficient for the flows in both convexly curved and recovery sections. This relationship describes the deviation of wake behavior from the flat-plate turbulent boundary layer due to convex curvature.

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“…Turbulent heat fluxes are measured using a specially designed and manufactured triple-wire probe (Kim and Simon, 1988). The probe supports two constant-temperature, 2.5 Itm diameter wires in an X-configuration for measuring the U -and Vcomponents of the flow.…”

Section: Test Facility and Instrumentationmentioning

confidence: 99%

Turbulent Transport Measurements in a Heated Boundary Layer: Combined Effects of Free-Stream Turbulence and Removal of Concave Curvature

Kestoras

Simon

1995

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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Turbulence measurements for both momentum and heat transport are taken in a boundary layer over a flat, recovery wall downstream of a concave wall (R=0.97m). The boundary layer appears turbulent from the beginning of the concave wall and grows over the test wall with negligible streamwise acceleration. The strength of curvature at the bend exit, δ99.5/R, is 0.04. The free-stream turbulence intensity is ∼8% at the beginning of the curve and is nearly uniform at ∼4.5% throughout the recovery wall. Comparisons are made with data taken in an earlier study, in the same test facility, but with a low free-stream turbulence intensity (−0.6%). Results show that on the recovery wall, elevated free-stream turbulence intensity enhances turbulent transport quantities such as -uv¯ and vt¯ in most of the outer part of the boundary layer, but near-wall values of vt¯ remain unaffected. This is in contrast to near-wall vt¯ values within the curve which decrease when free-stream turbulence is increased. At the bend exit, decreases of -uv¯ and vt¯ due to removal of curvature become more profound when free-stream turbulence intensity is elevated, compared to low-TI behavior. Measurements in the core of the flow indicate that the high levels of cross transport of momentum over the upstream concave wall cease when curvature is removed. Other results show that turbulent Prandtl numbers over the recovery wall are reduced to −0.9 when free-stream turbulence intensity is elevated, consistent with the rise in Stanton numbers over the recovery wall.

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Measurements of the Turbulent Transport of Heat and Momentum in Convexly Curved Boundary Layers: Effects of Curvature, Recovery and Free-Stream Turbulence

Cited by 12 publications

References 0 publications

Numerical investigation of bend and torus flows, part I : effect of swirl motion on flow structure in U-bend

Numerical investigation of bend and torus flows, part I : effect of swirl motion on flow structure in U-bend

Convex Curvature Effect on the WakeIncluding Recovery from the Curvature

Turbulent Transport Measurements in a Heated Boundary Layer: Combined Effects of Free-Stream Turbulence and Removal of Concave Curvature

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