Numerical Study of 2-D Vertical Water-Entry Problems Using Two-Phase SPH Method
- Lin Ma (Shanghai Jiao Tong University) | Hua Liu (Shanghai Jiao Tong University)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- June 2017
- Document Type
- Journal Paper
- 160 - 167
- 2017. The International Society of Offshore and Polar Engineers
- wedge, SPH, two-phase, Water entry
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- 48 since 2007
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A two-phase Smoothed Particle Hydrodynamics (SPH) method is used to simulate the early stage of the water entry of a 2-D wedge or a ship-section structure. From a comparison of the numerical results and the measured data, it is found that good agreement can be achieved. The variation of the velocity field, the pressure distribution, and the total hydrodynamic loads on the wedge are presented and discussed. The later stage of the cavity evolution for the wedge water entry and the formation of the entrapped air cavity for the ship-section water entry are simulated well by the two-phase SPH method.
Slamming on ships and offshore structures can induce local and global structural responses (Faltinsen, 2015). The mortal slamming force can damage the ships or offshore structures. A better understanding of the slamming force on the structure and the pressure distribution on the structure is important for the design and operation of ships and offshore platforms. The slamming stage is the initial stage of the water-entry problems, which includes the water landing of the spacecraft, aircraft ditching, and other applications in naval architecture and ocean engineering (Streckwall et al., 2007). The period of the slamming stage is extremely short, basically in the order of milliseconds, so the modelling slamming process requires pressure sensors with high-frequency responses in experiments and the high temporal resolution model in the numerical simulation.
In marine hydrodynamics, the entrapped air at the impact belongs to one of the important hydrodynamic phenomena associated with the water-entry-induced slamming of the ship, the sloshing-induced slamming in a liquefied natural gas (LNG) tank, and the steep-wave-induced impact on a vertical wall (Gao et al., 2012; Lugni et al., 2010a, 2010b; Gong et al., 2011). In recent years, mesh-free methods have played an important role in modelling hydrodynamic flows with the free surface. The Smoothed Particle Hydrodynamics (SPH) method is one of the mesh-free methods and has advantages in dealing with large deformation and breaking of the free surface (Oger et al., 2006). It was first utilized by Lucy (1977) to solve astrophysical problems. The applications of the SPH are mainly focused on fluid-dynamics-related areas including heat transfer, mass flow (Cleary, 1998), and multi-phase flows (Monaghan and Kocharyan, 1995). The SPH method has been developed into a competitive approach dealing with impulsive loading and large deformation events. Gong et al. (2009) adopted the SPH method with an improved approach for computing the pressure of the particles on the wall boundary condition.
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