Contribution to the study of three dimensional separation in turbulent incompressible flow

Experiments carried out to achieve a better understanding of the separation phenomenon in three dimensional flow are described. These experiments involved the use of models. In the first model is an ellipsoid cylinder of revolution consisting of half an ellipsoid with a cylindrical extension. Pressure taps at the wall allow the precise description of wall flow for a wide velocity range (from 10 to 90 m per second) and variable angle of attack (from 0 to 40 deg). Oil flow patterns allow detection of separation and transition lines. Based on these data and the work of Legendre a discussion about topology is presented. The second model studied is an oblate ellipsoid cylinder. Its front part is half an oblate ellipsoid. The rear part is a cylindrical extension. On this model and for the following conditions V sub 0 = 50 m per second and alpha = 30 deg external flow was probed with a five-hole probe and a three dimensional laser Doppler velocimeter. Mean and turbulent values in external flow have been characterized with details leeside in the beginning and developing vortex region. Pressure, velocity and rotational fields have permitted to materialize vortex structure. This analysis is completed by a careful examination of turbulent data.