An Experimental Investigation of the Effect of Riblets on a Transport Aircraft at Large Angles of Attack

The aerodynamic characteristic and flow structure of a transport aircraft with riblets are investigated by experiments in this work. The experiments of force measurements in a low-speed wind tunnel obtain the aerodynamic performance of the aircraft at a large angle of attack corresponding to the takeoff and climbing. The flow speed in the testing is up to 70m/s, and the angle of attack of the model is up to 20°. The measurements illustrate that the lift coefficient in the ribleted case could increase by 22.47%, and the drag coefficient could be reduced by 38.52%. In addition, a maximum of 79.42% incline in the lift-to-drag ratio is achieved. By the planar laser-induced fluorescence method, the qualitative flow visualizations of the flow field of wings and the wingtip vortex are demonstrated. Riblets weaken the flow separation of the boundary layer on the upper surface of the wing and enhance the flow attachment at a large angle of attack, moreover the size of the wingtip vortex is reduced. This indicates that the riblet surface inhibits the three-dimension effect of the finite wings.