An experimental study of cavity and Worthington jet formations caused by a falling sphere into an oil film on water

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Department of Mechanical Engineering-Engineering Mechanics


In this paper, air cavity and Worthington jet formations due to the entrance of a hydrophilic steel sphere into three different target liquids are studied. The liquids are water, silicone oil and silicone oil film on water. A high-speed camera is used to observe cavity and jet formations, and the resulting data is used to measure important parameters such as jet height, deep-seal time and deep-seal depth of the cavity. It was observed that no cavity forms after a hydrophilic sphere enters water. However, when a very thin layer of silicone oil is put on the water surface, a large air cavity and Worthington jet were observed. The results observed did not strongly vary with oil film thickness for the range studied in this work, and that as long as there is a layer of oil on water that wets the sphere surface before its entrance, an air cavity and jet will form. Additionally, an energy analysis is done for better understanding how kinetic energy of the sphere is transferred to the fluid. In the case of an oil film on water, the sphere lost its kinetic energy much more than when the target liquid was silicone oil or water. As a result, the fluid gained a significant amount of energy to form an air cavity which did not happen without oil film, and a Worthington jet of greater maximum height than the other two cases. Kinetic, surface and potential energies of the Worthington jet as it forms and reaches its peak are studied as well.

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© 2020 Elsevier Ltd. Publisher’s version of record: https://doi.org/10.1016/j.apor.2020.102319

Publication Title

Applied Ocean Research