A Calibration of the Preston Tube in Liquid Flow Systems.

Abstract

The justification of Preston tube usage is based on a universal similarity law that relates the velocity profile in fully developed pipe flow to that of a boundary layer associated with external flow. The Preston tube measures these velocities at the wall and when calibrated for flow in a pipe, provides a means of determining the local wall shear stress. This study is intended to extend the validity of this method to other working fluids such as liquids. Four separate size Preston tubes are used in three different experiments. The oil pipe provided a unique fluid in a narrow bore pipe and encompassed Reynolds numbers from just turbulent flow to 11600. Results indicated a calibration for oil that closely matched established air data. In the water tunnel experiment some difficulty was encountered for low speed flow but results above Re = 12800 precisely matched that for air. Each tube tested provided similar data and effectively proved the validity of Preston's method for water.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1979
Accession Number
ADA079876

Entities

People

  • Brian A. Maher

Organizations

  • Air Force Institute of Technology

Tags

Communities of Interest

  • Materials and Manufacturing Processes

DTIC Thesaurus Topics

  • Accuracy
  • Air Force
  • Boundary Layer
  • Channel Flow
  • Flow Separation
  • Fluid Dynamics
  • Layers
  • Measurement
  • Pipe Flow
  • Pressure Measurement
  • Research Facilities
  • Reynolds Number
  • Shear Stresses
  • Test Facilities
  • Turbulent Flow
  • Two Dimensional
  • Water Tunnels

Readers

  • Combustion and Flow Dynamics.
  • Fluid Dynamics.
  • Systems Analysis and Design