The turbulent behavior of a turbulent combined-convection boundary layer along a vertical heated plate in air has been experimentally investigated by using a particle image velocimetory (PINT). The reliability of turbulence measurements with a PIV for low-speed turbulent boundary layer flow in air is confirmed by comparison between fluctuating velocities measured with a PIV and a hot wire in the natural-convection boundary layer. Turbulence quantities measured in the combined-convection

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... layer show that the intensity of velocity fluctuation, especially in the outer layer, decreases with a slight aiding freestream. For the instantaneous velocity vectors, large-scale fluid motions moving from the maximum mean velocity location to the edge of the boundary layer are intermittently observed in the outer layer, and such fluid motions mainly generate turbulent energy of the boundary layer.