The laminar-turbulent transition of a mixing layer induced by oscillating flat plates at an exit of a two-dimensional nozzle was experimentally investigated. The mixing layer was formed between the jet which issued from the nozzle and the surrounding quiescent fluid. The plates oscillated vertically in relation to the mean flow. The disturbance was introduced by oscillating the plates at two vibrational modes. The one is due to symmetrical oscillating plates with respect to the nozzle center line, and the another is due to antisymmetrical oscillating plates with respect to the nozzle center line. The oscillation frequency was two orders of magnitude smaller than the fundamental frequency of the velocity fluctuation. The mixing layer was more expanded due to the disturbance introduced by the oscillating plates. The growth of turbulence was promoted due to the plate oscillation. The difference of oscillating motion did not affect the mixing layer downstream. The velocity fluctuation in the antisymmetrical oscillating mode was larger than that in the symmetrical oscillating mode.
