Solid Liquid Interaction PDF Print E-mail
Written by imanmirzaii   

Water Entry of a Solid Sphere


The impact of a solid object on to a liquid surface has been studied experimentally and theoretically for more than a century.However, this phenomenon is not well understood due to complex effects of solid-liquid momentum, cavity formation behind the solid object and capillary effects at the contact line between the surface of the solid and liquid. The study of solid-liquid interaction has a wide application in many industries such as water entry of the solid objects and designing ships, flying boats, seaplanes, etc. In this study, a numerical algorithm is developed for simulating the interactions between a liquid and solid object in presence of a free-surface flow. The presented model is that of the fast-fictitious-domain method integrated into the volume-of-fluid (VOF) technique used for tracking the free surface motion. The developed model considers the solid object as a fluid with a high viscosity resulting in a rigid motion of the object and solves the governing equations everywhere in the computational domain including the solid object. In this methodology, the application of the no-slip condition on the solid-liquid interface and the evaluation of the acting forces on the solid object are performed implicitly.


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The evolution of the falling of a sphere with a radius of 12.7 mm and a density 860 kg/m3 into a water free surface from our numerical simulations a) cross sectional images and b) 3D views; and c) experimental photographs by Aristoff, et al. (The water entry of decelerating spheres, 2010, Physics of Fluids 22, 8)




Free Fall of Two Consecutive Circular Disks:

When two circular disks are released consecutively from the rest in the same path, the upper disk may drift into the wake of the lower one which will result in the acceleration of the upper disk. This phenomenon, which occurs under a certain limit for the initial distance between the two disks, causes the accelerated disk to reach and touch the lower one. The falling of the two disks in contact while moving in the same path is very unstable. A slight flow disturbance will induce an angular displacement that in turn leads to an asymmetric wake which evidently gives rise to a strong destabilizing couple moment. Therefore, the two disks will be thrown apart from each other soon after their contact. The numerical simulation of this phenomenon is presented in this album


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The evolution of the free fall of two consecutive disks of 2.5 mm in diameter within a viscous liquid


Free Fall of a Circular Disk Within a Liquid:

The figure below shows a close view of the disk where the disk has reached almost to its terminal velocity. In this figure, the streamlines (left) and the velocity vectors (right) are depicted in order to provide a better insight of the motion. A recirculation zone can be observed near the disk (left). The velocity vectors demonstrate that the region of the liquid moved in the same direction as of the solid object extends from the disk center to a distance nearly the same as that of the disk diameter in the lateral direction. It should be mentioned that the solid zone should have a uniform velocity as seen in the figure.



Close view of the streamlines (left) and the velocity vectors (right) for a circular disk with a diameter of 2.5 mm and density 1.25×106 kg/m3 falling inside a liquid region with a density 106 kg/m3 at t=0.28 sec. The region of the liquid moved in the same direction as of the solid extends from the disk center to a distance nearly the same as of disk diameter in the lateral direction