Scale effects on marine cavitating flows: A study on a hydrofoil and a propeller operating in-behind condition

This paper investigates how scale effects affect the cavitating flow for two test cases of marine interest, using numerical simulations. The first is the Delft Twist 11 hydrofoil. Results show a larger cavity extent at full scale with earlier shedding; this behavior is related to changes in the pressure recovery on the foil at the closure region and a re-entrant jet that appears thicker and with higher momentum. Further modal analysis shows that scale effects are more pronounced in smaller-scale vapor structures while the large scale shedding dynamics is similar in both scales. The second case investigates a cavitating propeller operating in a ship wake, assessing both scale effects and cavitation test blockage using small and large domains. The wakefield is strongly influenced by scale and blockage effects, which modifies the transient propeller loading. Less sheet and tip vortex cavitation are predicted at full scale or with a larger domain at model scale. This leads to lower predicted pressure fluctuations and pulse levels. Finally, assessment of using wall function approach for full scale simulations shows it underpredicts sheet and tip vortex cavitation.