ON LARGE COHERENT STRUCTURES IN TWO-DIMENSIONAL TURBULENT WAKES.

A systematic study of turbulent, small-deficit, planar wakes behind various wake generators was carried out to investigate the structure and the universality of their self-preserving states. The results indicate that the normalized characteristic velocity and length scales depend on the initial conditions while the shape of the normalized mean velocity profile is independent of initial conditions or the nature of the wake generator. The normalized distributions of the longitudinal turbulence intensity, however, are dependent on the initial conditions. Linear, inviscid stability theory in which the divergence of the mean flow was taken into account predicts quite well the amplification and the transverse distributions of amplitudes and phases of externally imposed sinuous waves on a turbulent wake generated by a flat plate.