Turbulence characteristics of the flow downstream of a symmetric, plane sudden expansion

Measured values of the distribution of mean axial velocity, the rms of the corresponding fluctuations and energy spectra are reported in the region downstream of symmetric, plane sudden expansion. The results relate mainly to an expansion ratio of 3 but include results with a ratio of 2. The Reynolds numbers extend to 3865 and encompass a range of initial conditions from laminar to turbulent. The results are consistent with those of related investigations and, in addition, demonstrate the existence of asymmetry of the flow and its relationship to the growth of disturbance in the shear layers even at the comparatively high Reynolds numbers. It is argued that the length of the two regions of recirculation are related to each other and to the wavelength of the disturbance; these lengths are almost constant at high Reynolds numbers and this is explained.