Abstract
It is possible to control the spread of a plane jet passively by the vortices from a two-dimensional cylinder installed in the nozzle contraction. In this passive control method, two remarkable conditions to enhance the jet diffusion were found. One is the harmonic excitation and another one is the inharmonic excitation where the two distinctive spectral peaks at frequencies f1, f2 and low frequency f3. It is also known that the jet exhibits flapping motion at the low frequency f3. In this study, in order to compare the controlling effect of the jet diffusion by the wake from a small circular cylinder installed in the nozzle. As the results, the jet spread was found to be enhanced only by flapping motion of the jet in multiple control conditions in which diameter and location of the cylinder differed. However, the Strouhal frequency of the vortex in the cylinder wake in these enhancing conditions to was almost equal, and it became a value which was similar to the Strouhal frequency St_H≒0.45 of shear-layer mode.
