The paradigm water entry problem is the study of an object entering a quiescent water surface from the air. It is widely applied in naval industry, ocean engineering and ship manufacturing.   
In this study, a series of numerical experiments have been carried out on the water entry problem of three-dimensional multi-degree-freedom cylinders.   
The circular cylinder was released freely above the water with a specified inclined angle and velocity at entry.   
The hydrodynamics of the water entry problem have been investigated numerically.  
The Piecewise Linear Interface Calculation  (PLIC) schemes have been applied in conjunction with the Volume of Fluid (VOF) method to capture the interface in numerical calculations.  Overset meshes have been adopted to handle the moving object. The moving cylinder is contained in the body mesh with the background mesh representing the entire computational domain which includes the air and water. Tetrahedron meshes have been employed in the simulations. It should be noted that the numerical model is built on the framework of OpenFOAM which is an open-source C++ toolbox.  
Numerical results have been obtained. Transient flow and pressure distributions have been generated. The presence of air entrapment which has been reported experimentally has also been confirmed in the present study. The fluid physics of the oblique water entry problem such as the formation and development of the air entrapment has been explored.     
Furthermore, the lift and drag forces have been numerically calculated which are difficult to obtain experimentally by the high-speed camera.   
The transient positions and inclined angles of the moving circular cylinder have been found to be in good agreement with the experimental results.  
Parametric studies have been performed which examine the effects of inclined angle, impact velocity, surface wetness, head geometry of the free released cylinder and properties of the liquid.  
The major findings of the parametric study are: (1) the inclination angles after the cylinder enters the water is influenced by the moment of inertia of the cylinder which is determined by the geometry of the length-diameter ratio and the hollow structure of the cylinder. (2) a wetting surface of the moving object has less air entrapment. (3) a shallower penetration and a smaller inclination have been observed when the same cylinder enters a heavier liquid. (4) flat head (the side enters the water first) cylinder generates the larger resistances and traps more air compared to the dome and cone head. (5) cylinder with a larger inclination has a deeper penetration. 


A Numerical Study of Oblique Water Entry Problems

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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