Abstract
Turbulence structures in a natural-convection boundary layer in air above an isothermally heated round plate is experimentally investigated by using two-dimensional velocity vector measurements with PIV, the accuracy of which is verified through the comparison with a hot-wire measurement. Special attention is paid to the developing process of the boundary layer with flow convergence along a heated surface. The development of boundary layer causes the velocity gradients in the horizontal direction, and increases in upward velocity and the velocity fluctuations in the vicinity of the surface. This leads to the multi-layer structures of the boundary layer: the turbulence structures in the lower layer significantly differ from those in the upper layer; in the upper layer, thermal plume becomes dominant.
