Some improvements based on volume of fluid (VOF) method were done to exactly track the free surface with air pocket during the water entry. A continuum surface force (CSF) model was introduced to serialize the pressure on the interface of air and water. A convective term was added to minimize the numerical dissipation of volume fraction, and the level-set function was coupled to keep the sharpness of free surface. Oblique water entry problems of wedge with various inclination angles were simulated numerically based on the improved VOF method, and the characteristics of pressure and free surface were analyzed. The research shows that the free surface can be exactly reconstructed, and the same resolution can be realized in the improved VOF method through reducing 1/3 total number of mesh. The cavitation during oblique water entry is better reflected by the numerical simulation, and the slamming pressure peak agrees well with the published experimental data. When the deadrise angle is below 10°, an obvious air effect will appear. The error between numerical and experimental results is 10%, while it reaches up to 40% in the analytical solution. The results suggest that the air greatly influences the slamming pressure and the numerical high-precision results can be obtained through the improved VOF method.
XIE Hang,REN Huilong,TAO Kaidong,FENG Yikun
. Study on Oblique Water Entry of Wedge Applying
Improved Volume of Fluid Method[J]. Journal of Shanghai Jiaotong University, 2020
, 54(1)
: 20
-27
.
DOI: 10.16183/j.cnki.jsjtu.2020.01.003
［1］ZHAO R, FALTINSEN O. Water entry of two-dimensional bodies［J］. Journal of Fluid Mechanics, 1993, 246: 593-612.
［2］QIN H D, ZHAO L Y, SHEN J. A modified Logvinovich model for hydrodynamic loads on an asymmetric wedge entering water with a roll motion［J］. Journal of Marine Science and Application, 2011, 10(2): 184-189.
［3］XU G D, DUAN W Y, WU G X. Simulation of water entry of a wedge through free fall in three degrees of freedom［J］. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2010, 466(2120): 2219-2239.
［4］KRASTEV V K, FACCI A L, UBERTINI S. Asymmetric water impact of a two dimensional wedge: A systematic numerical study with transition to ventilating flow conditions［J］. Ocean Engineering, 2018, 147: 386-398.
［5］XIE H, REN H L, LI H, et al. Numerical prediction of slamming on bow-flared section considering geometrical and kinematic asymmetry［J］. Ocean Engineering, 2018, 158: 311-330.
［6］王易君, 李明海, 张中礼, 等. 基于VOF法的平底结构自由落体入水砰击载荷模拟［J］. 振动与冲击, 2017, 36(2): 185-189.
WANG Yijun, LI Minghai, ZHANG Zhongli, et al. Numerical simulation on the slamming load in the water-entry process of flatted-bottom body based on the method VOF［J］. Journal of Vibration and Shock, 2017, 36(2): 185-189.
［7］BRACKBILL J U, KOTHE D B, ZEMACH C. A continuum method for modeling surface tension［J］. Journal of Computational Physics, 1992, 100(2): 335-354.
［8］XIE H, REN H L, DENG B L, et al. Experimental drop test investigation into slamming loads on a truncated 3D bow flare model［J］. Ocean Engineering, 2018, 169: 567-585.
［9］ZHAO R, FALTINSEN O M, AARSNES J V. Water entry of arbitray two-dimensional sections with and without flow separation［C］//21st Symposium on Naval Hydrodynamics. Norway: Trondheim, 1996: 408-423.
［10］SUN H. A boundary element method applied to strongly nonlinear wave-body interaction problems［D］. Norway: Norwegian University of Science and Technology, 2007.
［11］BARJASTEH M, ZERAATGAR H, JAVAHERIAN M J. An experimental study on water entry of asymmetric wedges［J］. Applied Ocean Research, 2016, 58: 292-304.
［12］JUDGE C, TROESCH A, PERLIN M. Initial water impact of a wedge at vertical and oblique angles［J］. Journal of Engineering Mathematics, 2004, 48(3/4): 279-303.
［13］HU Z J, ZHAO X Z, LI M Y, et al. A numerical study of water entry of asymmetric wedges using a CIP-based model［J］. Ocean Engineering, 2018, 148: 1-16.
［14］遠山泰美. 任意形状物体の2次元水面衝撃計算法について［J］. 日本造船学会論文集, 1993, 1993(173): 285-291.
TOYAMA Yasumi. Two-dimensional water impact of unsymmetrical bodies［J］. Journal of the Society of Naval Architects of Japan, 1993, 1993(173): 285-291.
［15］WANG S, GUEDES SOARES C. Asymmetrical water impact of two-dimensional wedges with roll angle［J］. International Journal of Maritime Engineering, 2014, 156: 115-130.
