POD Analysis of Cavitation Dynamics in a Venturi Flow with Hemispherical Bumps

Cavitation is characterized by the periodic generation, growth, and collapse of vapor bubbles, which can significantly degrade the performance and durability of fluid machinery. This study experimentally investigates cavitation suppression in Venturi systems through the implementation of hemispherical bumps as a passive flow control strategy. The experiments were conducted over a Reynolds number range of 0.2 × 10⁵ to 1.1 × 10⁵, and cavitation behavior was analyzed using high-speed shadowgraph imaging combined with proper orthogonal decomposition (POD). POD analysis quantitatively decomposed the unsteady cavitation structures into dominant spatial modes and their associated temporal coefficients, enabling a detailed investigation of the dynamic features of cavitation. Compared to the base model, the configurations with hemispherical bumps showed reduced energy concentration in the dominant modes and shorter temporal fluctuation periods. These results suggest that the bumps contribute to suppressing the spatial extent and persistence of cavitation. The application of hemispherical bumps to the diverging section of the Venturi appeared to increase the local pressure near the throat, which delayed cavitation inception and shortened the overall cavitation length. While the detailed mechanism by which these bumps suppress cavitation is still under investigation, potential effects such as modified wake structures and altered pressure gradients will be discussed further in the presentation.