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Lee, Jae Hwa
Flow Physics and Control Lab
Research Interests
  • Turbulent Flow Physics and Control
  • Incompressible and Compressible Flows
  • Fluid-Structure Interaction
  • Multi-Phase Flow with Heat Transfer

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Structure of the turbulent boundary layer over a rod-roughened wall

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Title
Structure of the turbulent boundary layer over a rod-roughened wall
Author
Lee, Jae HwaLee, Seung-HyunKim, KyoungyounSung, Hyung Jin
Keywords
Direct numerical simulation; Roughness sublayer; Surface roughness; Turbulent boundary layer; Turbulent vortical structure
Issue Date
2009-12
Publisher
ELSEVIER SCIENCE INC
Citation
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, v.30, no.6, pp.1087 - 1098
Abstract
Turbulent coherent structures near a rod-roughened wall are scrutinized by analyzing instantaneous flow fields obtained from direct numerical simulations (DNSs) of a turbulent boundary layer (TBL). The roughness elements used are periodically arranged two-dimensional spanwise rods, and the roughness height is k/δ = 0.05 where δ is the boundary layer thickness. The Reynolds number based on the momentum thickness is varied in the range Reθ = 300-1400. The effect of surface roughness is examined by comparing the characteristics of the TBLs over smooth and rough walls. Although introduction of roughness elements onto the smooth wall affects the Reynolds stresses throughout the entire boundary layer when scaled by the friction velocity, the roughness has little effect on the vorticity fluctuations in the outer layer. Pressure-strain tensors of the transport equation for the Reynolds stresses and quadrant analysis disclose that the redistribution of turbulent kinetic energy of the rough wall is similar to that of the smooth wall, and that the roughness has little effect on the relative contributions of ejection and sweep motions in the outer layer. To elucidate the modifications of the near-wall vortical structure induced by surface roughness, we used two-point correlations, joint weighted probability density function, and linear stochastic estimation. Finally, we demonstrate the existence of coherent structures in the instantaneous flow field over the rod-roughened surface.
URI
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DOI
10.1016/j.ijheatfluidflow.2009.08.002
ISSN
0142-727X
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