The Effects of Longitudinal Roughness Elements Upon the Turbulent Boundary Layer,

Abstract

Velocity profiles and bursting statistics were measured in the presence of cylindrical longitudinal roughness elements (LREs) and compared to similar work by Johansen and Smith. An algorithm was devised to detect low speed streaks (LSS) from the hot-wire rake data, allowing an estimation of the LREs ability to reduce spatial randomeness of the sublayer structure. The velocity profiles agree with Johansen and Smith's result that the effects of the LREs are felt only for y(+) < or = 15. The analysis of the bursting statistics and LSS algorithm output shows that the flow relaxes back to a flat plate boundary layer between the LREs. A crude first approximation is that the LREs simply impose the no-slip boundary condition at an elevation equivalent to their diameter. While the LREs might serve as a nucleation site for the LSS, spatial randomness of the structure is effected only very close to the LREs.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 1988
Accession Number
ADA189285

Entities

People

  • J. B. Roon
  • R. F. Blackwelder

Organizations

  • University of Southern California

Tags

Communities of Interest

  • Materials and Manufacturing Processes
  • Sensors

DTIC Thesaurus Topics

  • Algorithms
  • Boundaries
  • Boundary Layer
  • Detectors
  • Diameters
  • Elements
  • Elevation
  • Engineering
  • Flow
  • Flow Visualization
  • Frequency
  • Hot Wire
  • Hydrogen
  • Layers
  • Leading Edges
  • Mechanical Engineering
  • Turbulent Boundary Layer

Readers

  • Fluid Dynamics.
  • Fluid Mechanics and Fluid Dynamics.