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.
Highlights
IntroductionWhen solid objects transit from one fluid region to another (e.g. from air to water), impact forces are exerted on the object and complex flow phenomena occur
When solid objects transit from one fluid region to another, impact forces are exerted on the object and complex flow phenomena occur
All spheres with a specific gravity of 1.056.66 formed a deep seal cavity regardless of surface coating or impact velocity
Summary
When solid objects transit from one fluid region to another (e.g. from air to water), impact forces are exerted on the object and complex flow phenomena occur. The quantification of impact forces and flow features has both academic and applied motivations. For naval vessels and projectiles, the motion of objects which land on a free water surface or pass through the interface depend greatly on impact forces. Another important application is associated with the delivery of oceanographic measurement devices. Often, these devices are dropped into the ocean waters from varying heights above the surface. Knowledge of the speed of their decent and their trajectory is required for correct interpretation of measured data
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
