Abstract:
This work quantifies the spatial distribution of air entrapped below rigid wedge, curved and flat specimens impacting water in free-fall. We have achieved unintrusive quantification by processing high-speed camera images using MATLAB® binarization and filtering techniques. Results have been quantified as a percentage area of the impacting specimen. For experiments with 300mm wide specimens, little to no air entrapment occurs for deadrise angles ≥2∘ and curved surfaces with radii ≤2.5m. The entire specimen is covered by an air layer for deadrise angles ≤0.5∘ or radii ≥10m. Importantly air entrapment was transitional/variable for deadrise angles between 0.5∘ and 2° or radii between 2.5 and 10m. Loading during the impacts has been used to compute experimental slamming coefficients. The cushioning is apparent in the wedge and curved slamming coefficients for β≤0.5∘ and R≥10m respectively, correlating to complete air layer entrapment. The wedge deadrise angle of 1° and curved radius of 5m experience elevated slamming coefficients, correlating to transitional spatial air entrapment. Finally, a flat plate slamming coefficient reduction occurs as width increases, suggesting an increase in air cushioning.