Study of transition phenomena in a straight channel with 40 to 1 aspect ration with and without imposed pulsations Part two: Reynolds number surveys
Smith, Bradley Joseph
Ligrani, Phillip M.
Subramanian, Chelakara S.
MetadataShow full item record
A channel with rectangular cross-section, 40 to 1 aspect ratio (height is0.0127 m) and 4.27 m test section length (336 channel lengths) is used to study the effects of imposed pulsations on laminar, transitional, and turbulent flow phenomena. Periodic velocity variations are produced in the test section using a single rotating vane located in the flow downstream of the test section. Survey data for Y/d of 0.50, 0.85, and 0.90 show how normalized average velocity and turbulence intensity data vary with Reynolds number for Reynolds numbers from 1100 to 3400 at Stokes numbers of 4.08 and 5.79 and Strouhal numbers from 0.033 to 0.121. These conditions are produced from pulsations imposed at 1 Hz and 2 Hz to show how transition develops both with and without imposed pulsations. Intermittency variations increase from near zero to one as Reynolds number changes from 1450- to 2100 for Y/d = 0.90, 0.85, and 0.50. Time-averaged magnitudes of the internalized longitudinal turbulence intensity increase significantly as RE changes from 1450 to 3100 at Y/d - 0.90. A maxima is reached near Re 2400. Afterwards these data show a decrease and level off in the turbulent region. At Y/d - 0.85, the same trend in normalized longitudinal turbulence intensity appears with a maxima appearing near re = 2300. For the enter of the channel (Y/d = 0.50), the maxima appears near Re = 2000. The normalized longitudinal turbulence intensity level in the turbulent region increase with Y/d. Of particular interest are conditions where the normalized longitudinal turbulence intensity is greater near the center of the channel than near the walls. This occurs for Reynolds numbers of 1500 to 2500. Spectra show evidence of intermittency and drastic increases in fluctuating energy starting at Re =1500 and continuing to Re = 1700.
Approved for public release; distribution is unlimited
Showing items related by title, author, creator and subject.
Transition phenomena in a straight channel with a 40 to 1 aspect ratio with and without imposed pulsations, part I: near-wall and central region profiles Morrow, Darrell S. (Monterey, California. Naval Postgraduate School, 1991-03);A channel with a rectangular cross-section, 40 to 1 aspect ratio (height is 0.01237 m), and 4.27 m test section (336 channel height) is used to study the effects of imposed pulsations on transitional flow phenomena. ...
Effects of 1, 2, 3 and 4 Hz imposed bulk flow oscillations on transition in a straight channel with 40 to 1 aspect ratio Koth, Howard Edwin (Monterey, California: Naval Postgraduate School, 1990-06);A channel with 40 to 1 aspect ratio and rectangular cross-section is used to study the effects of imposed oscillations on transition from laminar to turbulent flow. Oscillations are imposed using a single rotating vane ...
Effects of 1 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel Coumes, Thomas M. (Monterey, California. Naval Postgraduate School, 1989-12);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 ...