Recent Developments in Turbulence Management

The subjects covered in this volume include riblets, LEBUs (Large Eddy Break-Up devices), surface roughness, compliant surfaces and polymer additives. Riblets seem to be one of the most extensively studied devices in the past years. Reflecting this situation in the European Community, there are six papers on riblets covering their practical applications to aircraft and to a model ship, near-wall coherent structure of boundary layer and effects of flow three-dimensionality. Possibility of heat-transfer enhancement with riblets and potential use in the laminar flow are also investigated. An analytical model is developed for the boundary-layer with a LEBU device. Physical mechanisms of turbulent skin-friction reduction with LEBUs are reviewed in the light of some recent studies. The d-type roughness is investigated in conjunction with riblets for drag reduction. A correlation method of roughness parameters with the drag penalties is also presented. Two papers are devoted to further theoretical development of compliant surfaces in transition delay. Probably one of the most exciting recent developments in turbulence management is the use of compliant surfaces in the turbulent boundary layer. There are two papers describing some theoretical experimental work carried out on this subject in the U.S.S.R. Some further studies on the effects of polymer additives are also presented. The volume concludes with an edited record of the lively panel discussions which provided a useful forum to exchange views, plans for future research, collaborative work and industrial applications of drag reduction techniques.