Impacts of Surface Roughness on Cavitation Inception and Flow Dynamics*

Cavitation inception on a Venturi-type test section is investigated, using a small-scale water tunnel. High-speed imaging, combined with continuous back-lit illumination, is used to capture the microbubble formation on the diverging section of the test model. This study is pivotal for understanding the impacts of surface roughness on the location and dynamics of cavitation inception. The model’s diverging part, measuring 51.6 mm in length and 5 mm in width, is etched in the checkered pattern. The laser etching technique is utilized to obtain varying surface roughness ranging from 4 to 100 micrometers. The visualizations of the flow fields around the test model are analyzed using image processing techniques to identify the impact of roughness on the location of cavitation inception, as well as the dynamics of microbubbles produced by each cavitation bubble collapse. The presence of different roughness affects the cavitation process, by shifting the inception location and altering the flow dynamics.