Turbulent natural and mixed convection along a vertical plate

摘要

Measurements of turbulent boundary-layer air fow in natural and mixed convection adjacent to an isotermal vertical flat plate are reported. Laser-Doppler velocimeter and cold wire anemometer were used, respectivley, to measure simultaneously the mean turbulent velocity and temperature distributions and their turbulent fluctuations. The velocity and temperature distributions were measured for a temperature difference, DELTA T, of 30 deg C between the heated wall and the free stream air at a fixed location x chemical bounds 3 m (with a corresponding Grashof number Gr_x chemical bounds 8.55x10~(10)), and for a range of free stream velocities o m/s =< U_( infinity ) =< 0.41 m/s. The effect of small free stream velocity on the turbulent natural convection is examined. These results reveal that the introduction of saml free stream velocity on tubulent natural convection flow suppresses turbulence and decreases the heat transfer rate from the heated wall.