Turbulent kinetic energy balance in the wake of a self-propelled body

An experimental study of the turbulent wake of a self-propelled body in a wind tunnel is reported. A significant difference is formed between the turbulent kinetic energy balance in a wake with drag and in the wake of a self-propelled body: the production term is very small in comparison with the other terms of the turbulent kinetic energy balance, and this result seems to be typical of self-propulsion. The axial evolution of the wake radius and turbulent kinetic energy profiles are described. Sufficiently far downstream from the body, a self-similar profile is found. Particular attention is devoted to the turbulent kinetic energy balance; all the terms in the energy balance are evaluated experimentally.List of Symbols D diameter of the body - L axial length scale - l radial length scale - R radius of the body - r radial coordinate - r^* radius of the wake - U mean axial velocity scale - Û defect velocity - U_e freestream velocity - u fluctuating velocity scale - x axial coordinate - dissipation rate - = r/r^* radial relative direction - azimuthal coordinate - kinematic viscosity - density