An experimental study of transition to turbulence in vertical mixed convection flows

Journal Article · Tue Jan 31 23:00:00 EST 1989 · Journal of Heat Transfer (Transcations of the ASME (American Society of Mechanical Engineers), Series C); (United States)

DOI:https://doi.org/10.1115/1.3250631· OSTI ID:5341077

Krishnamurthy, R ^[1]; Gebhart, B ^[2]

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1. Catholic Univ. of America, Washington, D.C. (USA)
2. Univ. of Pennsylvania, Philadelphia (USA)

Results are reported from an experimental study of a mixed convection flow, that is combined forced and natural convection, undergoing transition to turbulence, adjacent to a vertical, uniform-heat-flux surface. Small and aiding forced convection effects were studied. The measurements, in air, were made at pressure levels ranging from 4.4 bars to 8 bars, at flux levels q in the range 14-1,300 W/m{sup 3}. The imposed free-stream velocities U{sub {infinity}} were around 5 cm/s. One objective was to determine any quantitative parameters that would predict the bounds of the transition region. Another was to measure disturbance growth characteristics during transition. Results show that, at a given U{sub {infinity}} the beginning of transition is not correlated by the local Grashof number Gr{sub x}* alone. An additional dependence on both the downstream location and pressure level was found. Thermal and velocity transitions were found to begin when the mixed convection parameter {epsilon}{sub M} reached a value of 0.18. Transition was found to be complete when the nondimensional convected energy in the boundary region {beta}q x/5k, reached a value of 7.10. These experimental results confirm the prediction of linear stability analysis, that aiding mixed convection stabilizes the flow, compared to pure natural convection flow. The data also support a physical explanation of these mechanisms.

• OSTI ID: 5341077
• Journal Information: Journal of Heat Transfer (Transcations of the ASME (American Society of Mechanical Engineers), Series C); (United States), Journal Name: Journal of Heat Transfer (Transcations of the ASME (American Society of Mechanical Engineers), Series C); (United States) Vol. 111:1; ISSN 0022-1481; ISSN JHTRA
• Country of Publication: United States
• Language: English

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