Study on the Fractal Characteristics of Cavitation Shedding over a Twisted Hydrofoil

Cavitation and cavitation erosion often occur and seriously threaten the safe and stable operation of hydraulic machinery. However, during the operation of hydraulic machinery, the cavitation flow field is often difficult to contact and measure, and the shedding and development characteristics of cavitation flow are unknown. This paper uses the Detached Eddy Simulation (DES) turbulence model and Zwart-Gerber-Belamri (ZGB) cavitation model to conduct numerical research on the cavitation flow of a twisted hydrofoil and verifies the effectiveness of numerical simulation by comparing it with experimental results. Then, based on the fractal dimension method, the number and fractal dimension of the main cavitation clusters in two different views are analyzed. The research results show that with the continuous flow of fluid, the cavitation at the tail of the hydrofoil periodically falls off, and the number of cavitation bubbles shows a strong randomness between 1 and 2. The fractal dimension method calculates that the frequency of cavitation bubbles falling off is 30 Hz. The fractal dimension of cavitation also fluctuates periodically. The fractal dimension of cavitation in the side view fluctuates between 1.30–1.38, and the fractal dimension of cavitation in the top view fluctuates between 1.31–1.42. The fractal dimension of the cavitation is closely related to the size and shape of the cavitation. By analyzing the relationship between the cavitation development process and the fractal dimension in the side view, we found the relationship between the development of cavitation in a cycle and the change of fractal dimension, which is of great significance to understanding the characteristics of cavitation flow through the image of the cavitation flow field.