Effects of 1 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel
Coumes, Thomas M.
Ligrani, Phillip M.
Subramanian, Chelakara S.
MetadataShow full item record
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 12.7 cm height, 50.8 cm width and 4.27 cm in length. Observations, videos and photographs of smoke patterns show different subcritical transition events including Tollmien-Schlicting waves, vortex-array type motion evidenced by smoke swirls and ribbon like patterns, turbulent spots and fully turbulent flow. Fluctuating intensity magnitudes relative to velocities from imposed unsteadiness are determined form 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 and extend over a wider range of Reynolds numbers compared to flows with no imposed unsteadiness.
Approved for public release; distribution is unlimited
Showing items related by title, author, creator and subject.
Ekaterinaris, J.A.; Platzer, M.F. (ASME, 1996-04);Unsteady, separated, high Reynolds number flow over an airfoil undergoing oscillatory motion is investigated numerically. The compressible form of the Reynolds-averaged governing equations is solved using a high-order, ...
Flow visualization studies in (1) a curved rectangular channel with 40 to 1 aspect ratio and (2) a straight channel with imposed bulk flow unsteadiness. Longest, Jerry Mark (Monterey, California. Naval Postgraduate School, 1989-06);Flow visualization results are presented which were obtained in a curved channel with mild curvature and 40 to 1 aspect ratio. Inside channel dimensions are 1.27 cm x 50.80 cm. For Dean numbers from 60 to 200 and angular ...
Effects of 2 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel. Greco, Francis J. (Monterey, California. Naval Postgraduate School, 1989);Laminar turbulent transition is studied in a straight channel with 2 Hz imposed bulk flow unsteadiness for Reynolds umbers of 1 100 to 3800 and Strouhal numbers of 0.121 to 0.035. Channel aspect ratio is 40 to 1 with 1.27 ...