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Buoyancy effect on forced convection in the leaf boundary layer
Author(s) -
KITANO M.,
EGUCHI H.
Publication year - 1990
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1990.tb01987.x
Subject(s) - grashof number , buoyancy , forced convection , airflow , natural convection , boundary layer , combined forced and natural convection , convection , mechanics , reynolds number , thermodynamics , materials science , physics , nusselt number , turbulence
Abstract. Mixed convection (forced convection plus free convection) in the leaf boundary layer was examined by air flow visualization and by evaluation of the boundary layer conductance at different leaf‐air temperature differences ( T L ‐ T A ) under low wind velocities. The visualized air flow was found to become more unstable and buoyant at higher T L ‐ T A . An ascending longitudinal plume was induced along the upper surface, and the air flow along the lower surface ascended after passing the trailing leaf edge. The air flow modified by buoyancy was considered to result in an increase in boundary layer conductance ( G A ) for mixed convection, which became higher with higher T L ‐ T A as compared with the conductance for pure forced convection without buoyancy. This increase in G A appeared larger at larger Grashof number (Gr) and at smaller Reynolds number (Re). The dependences of buoyancy effect on Gr and Re were related to ‘edge‐effects’.