FLOW INDUCED NOISE & CAVITATION CONTROL LAB.
AUTHENTIC DISCOVERY OF CAVITATION
01 Bubbly Flow by Air Injection on an Inclined Hydrofoil
02 Experimental Investigation of Artificial Supercavitation
Experimental investigation on drag characteristics and flow physics of ventilated supercavitating objects with different body shapes were conducted at the CNUCT. The test model consists of a disk-type cavitator with two different fore bodies (slender and blunt shape) and three different rear bodies (flat, shrinkage, and expanded shape). The drag forces acting on different body-combinations in fully wetted conditions are measured and the results show that the drag coefficients strongly depend on the body shapes. It explains in detail through particle image velocimetry measurements. The drag characteristics are systematically examined over a broad range of ventilation rates. The formation and the drag characteristics of the foamy and clear supercavity flow are investigated for different Froude number conditions. The results reveal that the drag of the blunt fore body is smaller than that of the slender fore body in foamy cavity conditions. In ventilated supercavity conditions, supercavity shapes according to Froude numbers are examined and corresponding effects on drag characteristics are analyzed. The results show that the drag coefficients of the models with the expanded rear body are larger than that of models with the flat and shrinkage rear bodies until the cavity covers the body.
03 Coherent Structure of Turbulent Cavitating Flow
In many practical submerged objects, various types of cavitation such as bubble, sheet, and cloud cavitation occur according to flow conditions. In spite of numerous theoretical, numerical, and experimental studies, there are still many problems to be solved such as induced noise and damage potential due to cavitation. In this paper, an experimental investigation on coherent structures and induced noise characteristics of partial cavitation on a two-dimensional hydrofoil is presented. Experiments that focused on the dynamics of cavitation clouds were conducted in a cavitation tunnel. Using high-speed visualization, the series process consisting of inception, growth, and desinence of the partial cavity was investigated. The noise generated during the process was also measured, and the correlation with the cavity pattern was examined. The results show that the periodic behavior of cavitation clouds is directly reflected in the noise characteristics. In addition, the visualization of coherent structures within the sheet and cloud cavity provides a qualitative understanding of hairpin vortices and their packets, which play a dominant role in turbulent cavitating flows.