Electrodiffusion diagnostics of wall shear stresses in impinging jets

Алексеенко, С. В.; Маркович, Д. М.

doi:10.1007/bf00252087

Cited by 32 publications

(30 citation statements)

References 9 publications

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“…Kataoka & Mizushina (1974), Kataoka et al (1982), and Alekseenko & Markovich (1994) used electrochemical probes and shear stress was calculated from the diffusion current. Bradshaw & Love used a flat Preston tube of height 0.38 mm, and Beltaos & Rajaratnam used a standard Preston tube with an outside diameter of 1.2 mm.…”

Section: ) ( ); Compared With Impingement-region Model (--) and Wall-mentioning

confidence: 99%

The wall shear stress produced by the normal impingement of a jet on a flat surface

2000

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A method for the theoretical determination of the wall shear stress under impinging jets of various configurations is presented. Axisymmetric and two-dimensional incompressible jets of a wide range of Reynolds numbers and jet heights are considered. Theoretical predictions from this approach are compared with available wall shear stress measurements. These data are critically evaluated based on the method of measurement and its applicability to the boundary layer under consideration. It was found that impingement-region wall shear stress measurements using the electrochemical method in submerged impinging liquid jets provide the greatest accuracy of any indirect method. A unique wall shear stress measurement technique, based on observing the removal of monosized spheres from well-characterized surfaces, was used to confirm the impinging jet analysis presented for gas jets. The technique was also used to determine an empirical relation describing the rise in wall shear stress due to compressibility effects in impinging high-velocity jets.

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Section: ) ( ); Compared With Impingement-region Model (--) and Wall-mentioning

confidence: 99%

The wall shear stress produced by the normal impingement of a jet on a flat surface

2000

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“…In the convergent jet, the maximum γmax occurred around r/De = 0.68, which falls in the range 0.6De -0.74De reported in the literature [33,38,39] for the case of a round impinging jet with a nozzle-to-wall distance H < 4 De. As for the lobed jets, the maximum value was observed in the CO/P nozzle jet at r/De = 0.58 and r/De = 0.53 in the MP and mP, respectively, and at r/De = 0.19 in both the MP and mP in the CO/H nozzle jet.…”

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confidence: 66%

“…For a high Reynolds number (Re = 41 600) and a nozzle-to-wall distance of H < 4D, two peaks were found in γ (or in wall shear stress τ = µ .γ ) distribution [38]. As for the Nu -distribution [20,23,26,35], the first peak in γ -distribution appeared at a distance from the stagnation point ranging from r = 0.56D to r = 0.74D, while the second peak was located at r = 1.9D [38,40] . The fact that peak-locations in γ -distribution closely match with those of Nu -distribution suggests that the wall shear stress and the local heat/mass transfer are closely linked.…”

Section: Introductionmentioning

confidence: 99%

“…The distribution of Nusselt numbers (Nu) generated by impinging jets has been characterized in numerous studies, but only a few investigations were devoted to the analysis of the corresponding wall shear rate (γ ) distribution [33,35,38,39]. Available data of Nu and γ were compared and revealed similarities in their distribution, on the number of peaks and their radial location.…”

Section: Introductionmentioning

confidence: 99%

“…For the same exit bulk-velocity Wb, the maximum wall shear rates in the CO/P and CO/H nozzle jets were almost two and three times higher, respectively, than that of the reference CONV nozzle jet. As the transfer mechanisms between the jet and the target wall are closely linked to the level of local skin-friction [38], the CO/H nozzle jet would appear to be an excellent candidate for passive strategies to enhance local heat and mass transfer in industrial applications.…”

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Impinging cross-shaped submerged jet on a flat plate: a comparison of plane and hemispherical orifice nozzles

et al. 2015

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To cite this version:Kodjovi Sodjavi, Brice Montagné, Pierre Bragança, Amina Meslem, Florin Bode, et al.. Impinging cross-shaped submerged jet on a flat plate: a comparison of plane and hemispherical orifice nozzles. Meccanica, Springer Verlag, 2015, pp.1-21. 10 AbstractIt is well known that the transfer of heat, mass and momentum to a wall by an impinging jet is partially linked to the way in which jet generation is realized. The organization of the vortices at the jet exit depends on the upstream conditions and on the geometry of the nozzle. Particle Image Velocimetry (PIV) and electrodiffusion techniques were used to investigate the characteristics of different impinging jets and the resulting wall shear rates and mass transfer. Two Cross-Shaped orifice jets, one produced by a plane orifice nozzle (i.e. a Cross-Shaped Orifice made on a flat Plate, CO/P) and the second by a hemispherical orifice nozzle (i.e. a Cross-Shaped Orifice made on a Hemisphere, CO/H), were compared to a reference round jet produced by a convergent nozzle. The distance between the jet exit and the target wall was equal to two nozzle equivalent diameters (De), based on the free orifice area. The Reynolds number, based on De and on the exit bulk-velocity, was 5620 for each flow. PIV measurements give an overall view of the flow characteristics in their free and wall regions. The switching-over phenomena observed in the CO/P nozzle case, and already described in the literature with similar nozzles, did not occur in the jet from the CO/H nozzle. Electrodiffusion measurements showed differences in the shape and level of radial distribution of the wall shear rates and mass transfer. One of the most important observations is the large difference in wall shear stress between the three jets. For the same exit bulk-velocity, the maximum wall shear rate in the CO/P and CO/H nozzle jets was almost two and three times higher, respectively, than that of the reference convergent jet. This higher wall shear rate is accompanied

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Estimation of agitator flow shear rate

Graham

Mehidi

2006

AIChE Journal

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Electrodiffusion diagnostics of wall shear stresses in impinging jets

Cited by 32 publications

References 9 publications

The wall shear stress produced by the normal impingement of a jet on a flat surface

The wall shear stress produced by the normal impingement of a jet on a flat surface

Impinging cross-shaped submerged jet on a flat plate: a comparison of plane and hemispherical orifice nozzles

Estimation of agitator flow shear rate

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