The sound produced when jets issued from a circular nozzle collide with a downstream ring coaxial with the jet is called a ring tone. The ring tone is investigated through experiments and direct sound computations. The inner diameters of the circular nozzle exit and the ring are both 30 mm. In the experiments, the frequency spectra of the ring tone are measured for various impingement lengths of 20-40 mm and jet velocities of 5-15 m/s. Measured data exhibit typical properties of self-sustained oscillations such as linear rise in peak frequency as the rise of the jet speed, multiple series of peaks, and mode jumps. In the computations, points discretely representing volumetric vortical regions are divided into locally connected groups of points that are separated from each other. This clustering enables the extraction of volumetric vortical regions in three-dimensional flow fields based on attributes defined on each point and tracking vortex structures selectively. By identifying strong vortex structures, the onset of self-sustained feedback oscillations in the ring tone is clarified from the view point of the throttling mechanism originally proposed for the hole tone, i.e., the coupling between the mass flow through the ring, vortex impingement, and global pressure fluctuation.
|International Journal of Computational Methods and Experimental Measurements
|Number of pages
|Published - Mar 2023
- aeroacoustics, direct sound computation, hole tone, ring tone, wind tunnel