Influence of Geometry on a Feedback-Free Fluidic Oscillator with Nonoutlet Facing Jets

In this paper, the effects of geometry constraints on the transient behavior of two impinging gas jets in 2D are being discussed. Limited in one dimension, the studied geometry consists of a rectangular area that at one side converges linearly toward a nozzle, which opens the geometry to ambient conditions. On both sides of the rectangle, jets are positioned in mirror symmetry opposite of each other. In the compressible flow field vortices are formed, which dependent on the angle of the jets and the geometrical confinements display stable or oscillatory behavior. Using high- speed schlieren photography, it is shown that the frequency of the oscillations is highly dependent on the geometry parameters. Furthermore, the method of extracting the oscillation frequency from schlieren images is discussed. Additionally, a numerical study of the flow field in 2D is presented. Employing a k - omega-SST URANS model, vortex formation and oscillations can be replicated. The dependency of the oscillation frequency on the geometry is shown to be in agreement between experiment and simulation. The absolute values of the oscillation frequency in the experiments are proportional to the numerical simulation and on average larger by a multiplication factor, which is in agreement with comparable studies.