The study on the structure of turbulent flow behind a hemisphere on the bed seems to offer a fundamental information on the energy loss in a boulder-bed stream or the flow characteristics around the river constructions such as the foot protection block.
In this paper, the mean-velocity distribution and turbulence characteristics behind a hemisphere on the bed are studied in detail. The equation of mean-velocity distribution is obtained in the connection between axisymmetric wake and logarithmic law, and the values are compared with those which are observed. The turbulent structure can be explained on the basis of examination on the distributions of Reynolds stress and turbulent kinetic energy, and the energy balance.