Friction measurement in zero and adverse pressure gradient boundary layer using oil droplet interferometric method

The oil droplet interferometric technique has been used to investigate the skin friction distribution along a zero and adverse pressure gradient boundary layer developing in the Laboratoire de M,canique de Lille wind tunnel. This experimental task was a part of the WALLTURB project, funded by the European Community, in order to bring significant progress in the understanding of near wall turbulence in boundary layers. Skin friction values close to 0.01 Pa have been measured with this optical method. A comparison with the results obtained with hot-wire anemometry and macro-PIV demonstrates the great potential of the oil droplet technique.