| Abstract | This paper introduces an experimental study in a cavitation tunnel on the wake/strut interaction of a podded propeller model (Dp=0.27m). The study includes surface pressure measurements on the strut around the leading edge, and visual investigations of cavitation tip vortices. The region of pressure measurements on the strut ranges from 0.6 to 1.2 of the propeller radius, Rp, and from the leading edge downstream to 0.4 of the chord length on both sides of the strut. Within this region, the pressure measurements at 56 different locations were realized by eight repeated tests with seven pressure transducers. The transducers were relocated before each repeated test. Each test consisted of five flow speeds which varied the advance coefficient, J, from 0.55 to 0.87. The pressure measured on the strut surface was decomposed into, represented by, and analyzed as three components: time average, phase average, and fluctuation components. In the visual investigation, the propeller tip vortex is bent by the leading edge of the strut when the vortex approaches the strut; the vortex then keeps a minimum distance from the leading edge of the strut while it moves along the leading edge of the strut away from the shaft centerline. After the tip vortex bends, stretches, and gradually fades out around the leading edge, it appears to be separated around the two sides of the strut and propagates downstream. The vortex turns from a continuously helical line into segments. The segmented vortex is compressed on one side of the strut and stretched on the other side. The vertical distance from the end of the segmented vortex to the shaft centerline on the stretched side remains a constant. However, this vertical distance increases on the compressed side. The lower the value of the advance coefficient, the faster this distance increases. The pressure measured at points located within 0.9 to 1.1 of the propeller radius shows that they were dominated by the Blade Passing Frequency (BPF). The measurements outside of this range rarely showed significant variation. The largest amplitude of pressure variation was found at the leading edge of the strut near 0 . 1 = p R for all tested advance coefficients. The location of the lowest pressure was found on the stretched side near the leading edge of the strut near the intersection of the pod and the strut. In cases of low advance coefficient, the pressure at some measurement points on or close to the leading edge on the compressed side demonstrated a double trough shape within a single period of filament impact. |
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