抄録
The utility of a dielectric barrier discharge (DBD) plasma actuator as a spread controller for a rectangular jet is investigated. The rectangular nozzle (75×10 mm) is used and actuators are placed on the long sides of the nozzle exit. The unsteady actuation of actuators is performed by changing the modulation frequency, the duty ratio and the phase difference. The flow visualization and the velocity measurements are conducted, and it is found that the spread of rectangular jet is controllable by the DBD plasma actuator. In the case that the actuators are operated in the same phase, the jet width depends on the modulation frequency rather than the duty ratio. The jet width becomes larger than that of base case when the dimensionless modulation frequency is less than about 1.36. In the case that the actuators are operated in the opposite phase, the jet width strongly depends on the duty ratio when the dimensionless modulation frequency is less than about 0.682. The largest spread in xy plane appears when the dimensionless modulation frequency is 0.125, the duty ratio is 10 %, and the phase difference is π. Its modulation frequency is nearly equivalent to 1/8 of the natural frequency of base case. In such a case, the alternative vortex grows near the nozzle exit and the jet width in xy plane becomes about three times larger than that of base case. It is also noticed that the smallest spread in xy plane appears when the dimensionless modulation frequency is 1.59, the duty ratio is 30 %. In this case, the definite vortex shedding is suppressed and small scale structure emerged near the nozzle exit, and the jet width in xy plane becomes about 20 % smaller than that of base case.
