DTIC ADA223396: Effects of 1 HZ Imposed pdf

DTIC ADA223396: Effects of 1 HZ Imposed

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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

• Creator/s: Defense Technical Information Center
• Date: 12/1/1989
• Year: 1989
• Book Topics/Themes: DTIC Archive, Coumes, Thomas M, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *CHANNEL FLOW, *LAMINAR FLOW, SMOKE, PATTERNS, PHOTOGRAPHS, ASPECT RATIO, REYNOLDS NUMBER, TURBULENT FLOW, THESES

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