Velocity and Density Effect on Impact Force during Water Entry of Sphere

Abstract

A careful experimental investigation has been performed to quantify the impact forces on a sphere that passes from an air region to a water region. The experiments allowed changes to a wide range of parameters, including the impact velocity, the sphere density, and surface wettability. In addition to quantifying the impact force, results have allowed a qualitative discussion of the difference in fluid flow behaviour in the vicinity of the sphere. It was found that the parameters, particularly the sphere density, determined whether the adjoining air cavity would be quasi-static or deep-sealed. Non-dimensionalizing the input parameters reveals that there is a singular relationship which allows quantification of the average force coefficient up to the time of cavity pinch-off. Finally, it was found that the formation of quasi-static cavities resulted in larger impact forces compared to the deep-seal cases. The difference in these force coefficients did not depend on the dimensionless parameter.

More Than 50 Years of Successful Continuous Temperature Section Measurements by the Global Expendable Bathythermograph Network, Its Integrability, Societal Benefits, and Future

“…More tools and methods are now being used to better understand the accuracy of XBT fall rates and temperature measurements. These tools include traditional side-by-side XBT and CTD comparisons (e.g., Thadathil et al, 2002;Hamon et al, 2012;Cowley et al, 2013;Cheng et al, 2018), tests in swimming pools and water tanks (e.g., Bringas and Goni, 2015), Geophysical Fluid Dynamics models (Abraham et al, 2012(Abraham et al, , 2014Gorman et al, 2014;Shepard et al, 2014), comparison with Argo and satellite altimetry data (DiNezio and , and temporal changes of biases (DiNezio and Good, 2011;Gouretski, 2012). A careful analysis of the different individual probe types is in progress (Reseghetti et al, 2018), as different probe types have different characteristics in probe design that may impact data quality.…”