Turbulence Control by Passive Means

In the last decades, a lot of effort has been directed towards manipulation of turbulent boundary layers by passive devices such as external manipulators (thin flat plates or aerofoil section devices embedded in the outer layer) and/or internal manipulators (small streamwise grooves acting directly on the inner region) for the purpose of reducing viscous drag. The former are commonly referred to as LEI3U s or BLADEs and the laHer riblets or grooves. Though the details of the mechanisms are not firmly understood, world-wide experimenta.! data are available and consistent enough in order to assert the potential of such devices for turbulent drag reduction. It should be noted that following on from recent and successful flight tests, the concept of using grooved surfaces is rather close to finding industrial applications. During the last few years, in Europe, there has been considerable interest in lookillg at the behaviour of such passi,'e turbulence manipulators. A lot of intense research, concerning both experimental and theoretical studies. has been carried out in some European research centres. For the last fi'e years. informal gatherings. called ,.\ 'orking Pi\l'ty i\Ieetings" , have been set up, once a year; the aim of these meetings is not only to bring together European researchers acti,'e in the field of turbulent drag reduction by passi"e means and to hear about recent de'c!opments but also to o u t1 ine sui tit ble directions for future research or collaborative programmes.

Texte du rabat

Proceedings of the 4th European Drag Reduction Meeting

Résumé
Proceedings of the 4th European Drag Reduction Meeting

Contenu
External Manipulators (LEBUs).- Balance of turbulent kinetic energy downstream a single flat, plate manipulator : comparisons between detailed experiments and modelling..- Manipulation and modelling of turbulent pipe flow : some parametric studies of single and tandem ring devices..- Large eddy simulation of manipulated boundary layer and channel flows..- The importance of LEBU device shape for turbulent drag reduction..- Internal Manipulators (Riblets).- Boundary layer flow visualisation patterns on a riblet surface..- Simultaneous flow visualisation and LDA studies over longitudinal micro-grooved surfaces..- Effects of longitudinal pressure gradients on turbulent drag reduction with riblets..- Synthesis of experimental riblet studies in transonic conditions..- Effect of riblets on either fully developed boundary layers or internal flows in laminar regime..- Internal and External Manipulators.- Turbulent boundary layer over a ribleted surface with tandem manipulators using surface drag balances..- List of referees.