Experimental characterization and modeling of cavitation in radial flow between two overlying plates with varying gaps
In the present study, we focus on characterizing and modelling cavitation physics in radial flow within a thin layer between two stationary plates. This geometry is relevant to aviation fuel pumps, where cavitation often leads to premature and unexpected material degradation and failure. In this geometry, the pressurized liquid flowing through a cylindrical feed nozzle is forced to turn ninety degrees and then move radially between two flat plates. The transition from axial to purely radial flow near the orifice results in extreme radial dilatation. If nuclei are present, this will lead to their rupture and the formation of cavitation bubbles. These bubbles form a cavitating cloud in the form of a disk surrounding the central inlet feed port, with a distinct boundary between the bubble cloud and liquid observed at the radial location of bubble collapse.
In our experimental effort, we quantified and compared cavitating disk behaviour for distilled water and dodecane (used as a surrogate for aviation fuel) across various gaps between the plates, ranging from 0.025 mm to 0.5 mm, and inlet-outlet pressure ratios in the range 4–11. By employing high-speed imaging alongside high-frequency and radial pressure measurements, we captured both the time-averaged and unsteady features of the disk-shaped cavitation cloud, specifically investigating the location of its abrupt radial collapse and the oscillatory behaviour of the cavity disk perimeter. In the seminar, a detailed discussion on the differences in radial cavitation behaviour between distilled water and dodecane will be presented.
In our modelling efforts, the spatial Rayleigh-Plesset equation was utilized to predict the abrupt radial collapse distance of the cavitation disk as a function of gap thickness between the plates. Additionally, we proposed a barotropic model for radial mean pressure profile prediction; this model showed good agreement when validated against experimental measurements across different gaps and inlet-outlet pressure ratios.
