Scale Model Test of an Isolated Turbofan Nacelle With Riblets

A one-seventh scale model of a high bypass turbofan inlet/nacelle was tested with and without V-groove riblets applied to the external surface. Tests were conducted in the French ONERA S1 transonic atmospheric wind tunnel in Modane. Before the test was finished riblets came off in two places and other problems with the riblet arose. These problems were partially solved by selective use of the drag data. Drag reductions up to 6.4%, depending on flow conditions, were obtained. Locally, reductions up to 8% were attained. In general, the higher drag reductions were attained when shocks were present.