Effects of 1 HZ Imposed Bulk Flow Unsteadiness on Laminar/Turbulent Transition in a Straight Channel

Abstract

Laminar/turbulent transition is studied in a straight channel with 1 Hz imposed bulk flow unsteadiness for Reynolds numbers of 1103 to 2715 and Strouhal numbers of 0.06045 to 0.02455. 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 evidence by smoke swirls and ribbon like patterns, turbulent and fully turbulent flow. Fluctuating intensity magnitudes relatives to velocities from imposed unsteadiness are determined from phase-averaged velocity traces. Of particular interest is whether the imposed unsteadiness advances or delays transition events. With the conditions that were investigated, transition events begin to occur at lower Reynolds numbers extend over a wider range of Reynolds numbers compared to flows with no imposed unsteadiness. Keywords: Imposed bulk flow unsteadiness, Laminar turbulent transition, Vortex, Turbulent spots, Theses.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1989
Accession Number
ADA223396

Entities

People

  • Thomas M. Coumes

Organizations

  • Naval Postgraduate School

Tags

Communities of Interest

  • Air Platforms
  • Materials and Manufacturing Processes
  • Sensors

DTIC Thesaurus Topics

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

Fields of Study

  • Physics

Readers

  • Fluid Mechanics and Fluid Dynamics.