A Redefined Hydraulic Diameter for Laminar Flow.

Abstract

For laminar, steady flow in ducts, the current definition of hydraulic diameter, Dh, does not accurately depict the non-uniform wall shear stress distribution around the perimeter of non-circular duct shapes. In this investigation, a new hydraulic diameter Dh(1), was empirically determined. It correlated friction factor data for many non-circular shapes to within approximately 2.4 % of the circular duct value. An experiment, using the AFIT oil Flow Rig Set-Up, was run to determine the effect of transition Reynolds number, Re(tr), and hydrodynamic entrance length, L(+), of replacing Dh with Dh(1). Transition Reynolds number and L(+) were determined, based on Dh and Dh(1) for a circular, square, and concentric annular duct. Transition Reynolds numbers, based on Dh, for the square and concentric annular ducts were approximately 12.5% lower than the circular duct Re(tr). The Re(tr), based on Dh(1), did not correlate well for the concentric annulus, but did correlate for the square duct. Keywords: Hydrodynamic length. (Theses)

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1986
Accession Number
ADA179511

Entities

People

  • Bruce J. Sutherland

Organizations

  • Air Force Institute of Technology

Tags

DTIC Thesaurus Topics

  • Air Force
  • Boundary Layer
  • Databases
  • Engineering
  • Experimental Data
  • Fluid Dynamics
  • Fluid Flow
  • Fluid Mechanics
  • Heat Transfer
  • Incompressible Flow
  • Laminar Flow
  • Measurement
  • Mechanical Engineering
  • Mechanics
  • Reynolds Number
  • Shear Stresses
  • Steady Flow

Readers

  • Fluid Mechanics and Fluid Dynamics.
  • Mechanical Engineering/Mechanics of Materials.