Understanding Cavitation Inception Mechanisms through Ultra-Fast Synchrotron X-ray Imaging

Understanding the fundamental mechanisms governing cavitation inception is crucial for optimizing curved surfaces such as propellers and mitigating potential damage caused by cavitation. This experimental study focuses on identifying and elucidating the factors that influence cavitation inception. To achieve this, the advanced measurement technique employing ultra-fast synchrotron X-ray imaging with exceptional temporal and spatial resolution is utilized, enabling high-definition visualization of the internal two-phase morphology. The flow is seeded to perform Particle Image Velocimetry (PIV) and Particle Tracking at a later stage, providing valuable insights into the inception mechanism and flow dynamics in proximity to the wall. At high flow rates, adverse pressure gradients result in local flow separation near the wall, giving rise to recirculating regions. Within these regions, microbubbles become entrapped close to the boundary layer, where they grow while appearing stagnant due to gas diffusion. Eventually, these microbubbles reach a critical stage and implode, generating additional microbubbles. This process is sustained by these microbubbles, or they get swept along the flow. The study also examines the impact of inlet turbulence on cavitation inception using a wire mesh fence. Interestingly, the turbulence delays the inception and only occurs at higher flow rates. The findings of this investigation are comprehensively discussed, shedding light on the intricate mechanisms driving cavitation inception.