A dynamical and visual study on the oscillatory turbulent boundary layer

Experimental studies of the purely oscillatory turbulent boundary layer were first conducted by Jonsson (1963). Hayashi et al. (1980) conducted detailed measurements regarding turbulent characteristics, taking into account the visualization of the transition to turbulence. The present investigation is concerned with a number of questions which have not been sufficiently clarified in previous studies. Experiments were conducted in a large water tunnel of the Lundgren-Sorensen type. The apparatus employed forms a U-shaped tube with a horizontal tunnel. By means of a piston the water is made to oscillate in the U-shaped tube. Attention is given to turbulent shear stress profiles, time variations of turbulent shear stress, and aspects of flow visualization and observation. It is found that two mechanisms are responsible for the generation of turbulence in purely oscillatory boundary layers. After the generation of large-scale eddies turbulence in the boundary layer decreases rapidly.