Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a ...Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems. The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement. Improving pressure results is clearly an important next step for research.展开更多
The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping a...The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping analysis involving severe flow fluctuations is still quite challenging even for the conventional RANS method. Particle method has been viewed as alternative for such analysis especially those involving deformable boundary, wave breaking and fluid fragmentation around hull shapes. In this paper, the weakly compressible smoothed particle hydrodynamics(WCSPH), a fully Lagrangian particle method, is applied to simulate the symmetric radiation problem for a stationary barge treated as a flexible body. This is carried out by imposing prescribed forced simple harmonic oscillations in heave, pitch and the two-and three-node distortion modes. The resultant,radiation force predictions, namely added mass and fluid damping coefficients, are compared with results from 3-D potential flow boundary element method and 3-D RANS CFD predictions, in order to verify the adopted modelling techniques for WCSPH.WCSPH were found to be in agreement with most results and could predict the fluid actions equally well in most cases.展开更多
Kernel gradient free-smoothed particle hydrodynamics （KGF-SPH） is a modified smoothed particle hydrodynamics （SPH） method which has higher precision than the conventional SPH. However, the Laplacian in KGF-SPH is ...Kernel gradient free-smoothed particle hydrodynamics （KGF-SPH） is a modified smoothed particle hydrodynamics （SPH） method which has higher precision than the conventional SPH. However, the Laplacian in KGF-SPH is approximated by the two-pass model which increases computational cost. A new kind of discretization scheme for the Laplacian is proposed in this paper, then a method with higher precision and better stability, called Improved KGF-SPH, is developed by modifying KGF-SPH with this new Laplacian model. One-dimensional （1D） and two-dimensional （2D） heat conduction problems are used to test the precision and stability of the Improved KGF-SPH. The numerical results demonstrate that the Improved KGF-SPH is more accurate than SPH, and stabler than KGF-SPH. Natural convection in a closed square cavity at different Rayleigh numbers are modeled by the Improved KGF-SPH with shifting particle position, and the Improved KGF-SPH results are presented in comparison with those of SPH and finite volume method （FVM）. The numerical results demonstrate that the Improved KGF-SPH is a more accurate method to study and model the heat transfer problems.展开更多
Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(...Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(SPH)method under the Lagrange framework is adopted to simulate the breaking bow wave of the KCS ship model.In order to improve the computational efficiency,the inflow and outflow boundary model is used to establish a numerical tank of current,and a numerical treatment for free surface separation is implemented.Numerical simulations are carried out at Fr=0.35,0.40,0.5,0.6,and different types of wave breaking such as spilling breaker,plunging breaker,and scars are captured by the SPH method,which is consistent with the experimental result,demonstrating that the present SPH method can be robust and reliable in accurately predicting the breaking bow wave phenomenon of high-speed ships.Furthermore,the wave elevation and velocity field in the bow wave region are analyzed,and the evolution of the bow wave breaking is provided.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No. 10572041 and 50779008
文摘Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems. The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement. Improving pressure results is clearly an important next step for research.
基金funded by the Ministry of Higher Education(MOHE)of Malaysia under the Fundamental Research Grant Scheme(FRGS)No.FRGS17-042-0608
文摘The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping analysis involving severe flow fluctuations is still quite challenging even for the conventional RANS method. Particle method has been viewed as alternative for such analysis especially those involving deformable boundary, wave breaking and fluid fragmentation around hull shapes. In this paper, the weakly compressible smoothed particle hydrodynamics(WCSPH), a fully Lagrangian particle method, is applied to simulate the symmetric radiation problem for a stationary barge treated as a flexible body. This is carried out by imposing prescribed forced simple harmonic oscillations in heave, pitch and the two-and three-node distortion modes. The resultant,radiation force predictions, namely added mass and fluid damping coefficients, are compared with results from 3-D potential flow boundary element method and 3-D RANS CFD predictions, in order to verify the adopted modelling techniques for WCSPH.WCSPH were found to be in agreement with most results and could predict the fluid actions equally well in most cases.
文摘Kernel gradient free-smoothed particle hydrodynamics （KGF-SPH） is a modified smoothed particle hydrodynamics （SPH） method which has higher precision than the conventional SPH. However, the Laplacian in KGF-SPH is approximated by the two-pass model which increases computational cost. A new kind of discretization scheme for the Laplacian is proposed in this paper, then a method with higher precision and better stability, called Improved KGF-SPH, is developed by modifying KGF-SPH with this new Laplacian model. One-dimensional （1D） and two-dimensional （2D） heat conduction problems are used to test the precision and stability of the Improved KGF-SPH. The numerical results demonstrate that the Improved KGF-SPH is more accurate than SPH, and stabler than KGF-SPH. Natural convection in a closed square cavity at different Rayleigh numbers are modeled by the Improved KGF-SPH with shifting particle position, and the Improved KGF-SPH results are presented in comparison with those of SPH and finite volume method （FVM）. The numerical results demonstrate that the Improved KGF-SPH is a more accurate method to study and model the heat transfer problems.
基金The Guangdong Basic and Applied Basic Research Foundation(2024B1515020107)the National Natural Science Foundation of China(Grant Nos.52171329)+1 种基金the State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact(Grant No.NOLGD-SKL-202201)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.231gbi023).
文摘Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(SPH)method under the Lagrange framework is adopted to simulate the breaking bow wave of the KCS ship model.In order to improve the computational efficiency,the inflow and outflow boundary model is used to establish a numerical tank of current,and a numerical treatment for free surface separation is implemented.Numerical simulations are carried out at Fr=0.35,0.40,0.5,0.6,and different types of wave breaking such as spilling breaker,plunging breaker,and scars are captured by the SPH method,which is consistent with the experimental result,demonstrating that the present SPH method can be robust and reliable in accurately predicting the breaking bow wave phenomenon of high-speed ships.Furthermore,the wave elevation and velocity field in the bow wave region are analyzed,and the evolution of the bow wave breaking is provided.
