The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results...The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results,the MPS has poor perfor-mance in convergences with a time step size.Therefore,users of the MPS need to tune numerical parameters to ft results into benchmarks.However,such tuning parameters are not always valid for other simulations.We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem(i.e.,an MPS-slamming condition).The MPS-slamming condition is represented by an MPS-slamming number,which provides the optimum time step size once the MPS-slamming number,slamming velocity,deadrise angle of the wedge,and particle size are decided.The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition,and the use of the same MPS-slamming number provides a similar fow.展开更多
In this paper, wave focusing based on a coordinate transformation is proposed. It is known that the 2-dimensional wave equation which governs a shallow water problem in a potential theory can keep invariance under coo...In this paper, wave focusing based on a coordinate transformation is proposed. It is known that the 2-dimensional wave equation which governs a shallow water problem in a potential theory can keep invariance under coordinate transformation. Once equivalent medium parameters are obtained so as to keep the invariance, wave rays can be arbitrarily designed. We show the design of equivalent medium for wave squeezing to focus waves on a specific domain. Numerical computations are carried out by a finite element based software COMSOL Multiphysics. Results show good agreement between predictions from the theory and computations. It can be applied for a wide range of frequency because the proposed method is able to be applied regardless of the frequency.展开更多
A design method of a negative refractive index for free surface water waves in deep water is presented. To obtain a condition of a negative index, an analogy between water waves in a water channel and electric waves i...A design method of a negative refractive index for free surface water waves in deep water is presented. To obtain a condition of a negative index, an analogy between water waves in a water channel and electric waves in an electric circuit is employed. An analytical solution of waves around a periodic array of rectangular columns is obtained by a circuit analysis. Attention is not focused on columns but a space among columns, and then the space is regarded as the water channel. Therefore, the circuit analysis can be applied to water waves. One channel is treated as a unit structure and a number of channels are periodically cascaded as a network. The negative refraction and backward waves by a network of the water channels are shown. Since the negative refraction might occur even around simple periodic structures, it is meaningful to understand wave phenomenon around offshore structures and develop innovative technology.展开更多
文摘The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results,the MPS has poor perfor-mance in convergences with a time step size.Therefore,users of the MPS need to tune numerical parameters to ft results into benchmarks.However,such tuning parameters are not always valid for other simulations.We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem(i.e.,an MPS-slamming condition).The MPS-slamming condition is represented by an MPS-slamming number,which provides the optimum time step size once the MPS-slamming number,slamming velocity,deadrise angle of the wedge,and particle size are decided.The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition,and the use of the same MPS-slamming number provides a similar fow.
文摘In this paper, wave focusing based on a coordinate transformation is proposed. It is known that the 2-dimensional wave equation which governs a shallow water problem in a potential theory can keep invariance under coordinate transformation. Once equivalent medium parameters are obtained so as to keep the invariance, wave rays can be arbitrarily designed. We show the design of equivalent medium for wave squeezing to focus waves on a specific domain. Numerical computations are carried out by a finite element based software COMSOL Multiphysics. Results show good agreement between predictions from the theory and computations. It can be applied for a wide range of frequency because the proposed method is able to be applied regardless of the frequency.
文摘A design method of a negative refractive index for free surface water waves in deep water is presented. To obtain a condition of a negative index, an analogy between water waves in a water channel and electric waves in an electric circuit is employed. An analytical solution of waves around a periodic array of rectangular columns is obtained by a circuit analysis. Attention is not focused on columns but a space among columns, and then the space is regarded as the water channel. Therefore, the circuit analysis can be applied to water waves. One channel is treated as a unit structure and a number of channels are periodically cascaded as a network. The negative refraction and backward waves by a network of the water channels are shown. Since the negative refraction might occur even around simple periodic structures, it is meaningful to understand wave phenomenon around offshore structures and develop innovative technology.
