Article
Turbulent flow around a rotating stepped cylinder
Department of Mechanical Engineering, Inha University, Incheon, Incheon, South Korea
Physics of Fluids (Impact Factor: 2.03). 04/2002; 14(4). DOI: 10.1063/1.1455625 Source: OAI
ABSTRACT
Direct numerical simulation (DNS) of turbulent flow around a rotating cylinder with two backwardfacing steps axisymmetrically mounted in the circumferential direction was performed and compared with DNS of plane backwardfacing step flow (PBSF) of Le [J. Fluid Mech. 330, 349 (1997)]. The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. It turned out that the current flow shows flow structures quite similar to those of PBSF downstream of the step, even though configurations of the two flows are totally different from one another. The stepped cylinder appears to be a costeffective tool in the generation of flow structures similar to those of PBSF. (C) 2002 American Institute of Physics.
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 "The ratios among the roughness height ℎ, the roughness interval í µí¼, and the reattachment length í µí°¿ re are also shown. on a turbulent TaylorCouette flow (TCF) with regular roughness elements (other than DNS for stepped cylinder [13] [14]). As is well known, TCF occurs when fluid is contained between two concentric independently rotating cylinders and often provokes Taylor vortices due to Coriolis instability when the inner cylinder rotates at relatively high speed [15] [16]. "
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Article: Patch and Whole of Surface MassTransfer Rate Measurements on a Stepped Rotating Cylinder Electrode
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ABSTRACT: A recently developed whole of surface electroplating technique was used to obtain masstransfer rates in the separated flow region of a stepped rotating cylinder electrode. These data are compared with previously reported masstransfer rates obtained with a patch electrode. It was found that the two methods yield different results, where at lower Reynolds numbers, the masstransfer rate enhancement was noticeably higher for the whole of the surface electrode than for the patch electrode. The location of the peak mass transfer behind the step, as measured with a patch electrode, was reported to be independent of the Reynolds number in previous studies, whereas the whole of the surface electrode shows a definite Reynolds number dependence. Large eddy simulation results for the recirculating region behind a step are used in this work to show that this difference in behavior is related to the existence of a much thinner fluid layer at the wall for which the velocity is a linear junction of distance from the wall. Consequently, the diffusion layer no longer lies well within a laminar sublayer. It is concluded that the patch electrode responds to the wall shear stress for smooth wall flow as well as for the disturbed flow region behind the step. When the whole of the surface is electroactive, the response is to mass transfer even when this is not a sole function of wall shear stress. The results demonstrate that the choice of the masstransfer measurement technique in corrosion studies can have a significant effect on the results obtained from empirical data.