Abstract
This paper deals with the investigation of wake-disturbed boundary layers on a flat-plate model with an elliptic leading edge. The wakes are generated by the transversely moving bars in front of the test model. The main focus of this paper is how the wake passage affects the transitional behavior of the boundary layer under the influence of favorable and adverse pressure gradients. The flow accelerating and decelerating devices simulate the pressure gradients on the suction surface of the turbine rotor or nozzle. A spoked-wheel-type wake generator is used to simulate the unsteady flow field over the suction surface of a turbine rotor or nozzle by changing the direction of the rotation of the wake-generator. Detailed boundary layer measurements are performed by use of hot-wire anemometry, which allows analysis of the raw signals of the velocity, ensemble-averaged velocity, turbulence intensity and time-averaged intermittency factors. It is found that the effect of the calmed region, which is the laminar-like flow occurring immediately behind a turbulent spot, delays the transition in the region between wakes.
