Effects of 2HZ Imposed Bulk Flow Unsteadiness on Laminar/Turbulent Transition in a Straight Channel

Abstract

Laminar/turbulent transition is studied in a straight channel with 2 Hz imposed bulk flow unsteadiness for Reynolds numbers of 1100 to 3800 and Strouhal numbers of 0.121 to 0.035. Channel aspect ratio is 40 to 1 with 1.27 cm height, 50.8 cm width and 4.27 m length. Observations, videos, and photographs of smoke patterns show different subcritical transition events including Tollmien-Schlichting waves, vortex-array type motion evidenced by smoke swirls, ribbon-like patterns, turbulent spots, and fully turbulent flow. Fluctuating intensity magnitudes relative to velocities from imposed unsteadiness are determined from phase-averaged velocity traces. With 2 Hz unsteadiness, transition events begin to occur at lower Reynolds numbers and extend over a wider range of Reynolds numbers compared to flows with no imposed unsteadiness.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1989
Accession Number
ADA223028

Entities

People

  • Francis J. Greco

Organizations

  • Naval Postgraduate School

Tags

Communities of Interest

  • Air Platforms
  • Materials and Manufacturing Processes
  • Sensors

DTIC Thesaurus Topics

  • Acquisition
  • Boundary Layer
  • Computational Fluid Dynamics
  • Data Acquisition
  • Flow Visualization
  • Fluid Dynamics
  • Fluid Flow
  • Fluid Mechanics
  • Hydrodynamics
  • Measurement
  • Mechanical Engineering
  • Mechanics
  • Personal Computers
  • Photographs
  • Reynolds Number
  • Turbulent Flow
  • Turbulent Mixing

Fields of Study

  • Physics

Readers

  • Fluid Mechanics and Fluid Dynamics.