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Experiments were performed in the highly turbulent and disturbed flow over a bluff plate with a long splitter plate in its plane of symmetry. The flow separates at the sharp bevelled edge of the bluff plate, forms a free shear layer on top of the reverse-flow region which is bounded on its other side by the splitter plate, and reattaches on the splitter plate over a narrow region curved in spanwise direction. Downstream of reattachment the shear flow adjusts slowly to the wall boundary conditions.Measurements of mean velocity, Reynolds-shear-stress and Reynolds-normal-stress distributions were carried out by hot-wire and pulsed-wire anemometry. The latter technique was used in those regions of the flow where reverse flow occurred or where the flow was highly turbulent. Spectra and integral lengthscales were measured to investigate the state and structure of the flow. The large-eddy structure in the inner region of the flow had lengthscales in the two cross-stream directions which were approximately equal, indicating a fast break-up of spanwise structures just downstream from separation.Mean and fluctuating quantities showed a self-similar behaviour in a short region upstream of reattachment and ‘profile similarity’ in the separated shear layer and along the splitter plate downstream from reattachment. Probability-density distributions of skin friction were measured and used to calculate mean and fluctuating values. No flapping of the reattaching shear layer could be observed. Pulsed-wire measurements revealed that the logarithmic law of the wall does not hold either in the reverse-flow region or in a region about half the length of the bubble downstream from reattachment.

The first in a new series of European research conferences in mechanics was held in Berlin on 5 and 6 April 1965. The subject was the Coanda effect, or boundary layers and jets on highly curved walls. Participation was restricted to about 40 people, invited on the basis of their active interest in the subject. These Colloquia are intended to have an informal, workshop-like, character, and formal papers are not normally available, nor will any full proceedings be published. The first author was the chairman of the Colloquium. The following account of the scientific developments of the Colloquium has been prepared to make them widely available. The references quoted give further details of the work discussed at the Colloquium and of related previous work.

This survey covers recent developments and applications of four skin-friction measurement techniques (oil-film interferometry, wall hot wire, surface fence and wall pulsed wire). Comparisons of the techniques with each other and with other methods are presented. Applications in attached and separated fully turbulent boundary layers and in highly accelerated laminar-like flows will be shown to demonstrate the application range and the limits of the various techniques.

The following is an investigation into the effects of small changes in the static pressure distribution on the development of an axisymmetric, incompressible, turbulent boundary layer with incipient separation. The pressure distribution was closely controlled to study three cases, in which the skin friction was either approximately zero, slightly negative, or slightly positive along a fixed length. Mean flow and turbulence structure in air were measured using pulsed-wire and hot-wire anemometry.These measurements show characteristic properties of steady turbulent boundary layers both on the verge of separation and with a long, shallow separation bubble. There is an asymptotic velocity defect law near separation. A linear relationship between χW, the wall value of the reverse-flow parameter, and the form parameter H12 suggests the importance of χW in characterizing the boundary layer. The occurrence of the first reverse-flow events coincides with the vanishing of the logarithmic law, the asymptotic mean velocity profile, and a sudden drop in the values of the skewness SW and the flatness FW of the skin friction. This implies that the presence of instantaneous reverse flow is associated with a complete change in the nature of the near-wall flow, well upstream of mean separation. As the three cases were investigated in a single test section under closely controlled conditions with the same experimental techniques, this data set is well suited to a sensitivity study. It is possible to show the effect of small changes in the upstream pressure gradient on the separation region and to distinguish the effect of mean reverse flow from that of the adverse pressure gradient. This effect of the reverse flow is displayed most clearly in a plateau in $\overline{u^{\prime 2}}$ near the wall and in unusual behaviour of the skewness and the flatness profiles over the inner half of the boundary layer.