Owing to the influence of the viscosity of the flow field,the strength of the shedding vortex decreases gradually in the process of backward propagation.Large-scale vortexes constantly break up,forming smaller vortexe...Owing to the influence of the viscosity of the flow field,the strength of the shedding vortex decreases gradually in the process of backward propagation.Large-scale vortexes constantly break up,forming smaller vortexes.In engineering,when numerical simulation of vortex evolution process is carried out,a large grid is needed to be arranged in the area of outflow field far from the boundary layer in order to ensure the calculation efficiency.As a result,small scale vortexes at the far end of the flow field cannot be captured by the sparse grid in this region,resulting in the dissipation or even disappearance of vortexes.In this paper,the effect of grid scale is quantified and compared with the viscous effect through theoretical derivation.The theoretical relationship between the mesh viscosity and the original viscosity of the flow field is established,and the viscosity term in the turbulence model is modified.This method proves to be able to effectively improve the intensity of small-scale shedding vortexes at the far end of the flow field under the condition of sparse grid.The error between the simulation results and the results obtained by using fine mesh is greatly reduced,the calculation time is shortened,and the high-precision and efficient simulation of the flow field is realized.展开更多
In this paper a series of numerical simulations are performed to investigate the vortex shedding mechanism for a solitary wave propagating over a submerged breakwater by use of Reynolds averaged Navier-Stokes （RAINS...In this paper a series of numerical simulations are performed to investigate the vortex shedding mechanism for a solitary wave propagating over a submerged breakwater by use of Reynolds averaged Navier-Stokes （RAINS） model combined with a k-ε model. Flows of different Reynolds numbers up to Re = 1.4 × 10^5 corresponding to varying incident wave heights are considered in which the characteristic fluid velocity is represented by the maximum horizontal velocity above the submerged breakwater. For the verification of the accuracy of the numerical model, the incident waves and the velocity field in the vicinity of the breakwater are compared with experimental data. The result shows that the model is capable of describing vortex shedding for a solitary wave propagating over a rectangular submerged breakwater. Key features of vortex generation, evolution and dissipation are investigated. It is found that the vortex shedding and their evolution due to separated boundary layer over the breakwater are strongly related to the Reynolds number. A considerable number of vortices and complicated vortex pattern are observed as the Reynolds number increases.展开更多
本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算...本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算涡振时程响应,并通过算例验证了该方法的可行性。与传统的连续模型和随机振动理论计算桥梁涡激响应方法相比,时程计算可以考虑多振型的组合作用,结构非线性等多种影响,具有更大的灵活性。展开更多
基金Project supported by the National Key Project,China(Grant No.GJXM92579)the National Natural Science Foundation of China(Grant No.12072232)。
文摘Owing to the influence of the viscosity of the flow field,the strength of the shedding vortex decreases gradually in the process of backward propagation.Large-scale vortexes constantly break up,forming smaller vortexes.In engineering,when numerical simulation of vortex evolution process is carried out,a large grid is needed to be arranged in the area of outflow field far from the boundary layer in order to ensure the calculation efficiency.As a result,small scale vortexes at the far end of the flow field cannot be captured by the sparse grid in this region,resulting in the dissipation or even disappearance of vortexes.In this paper,the effect of grid scale is quantified and compared with the viscous effect through theoretical derivation.The theoretical relationship between the mesh viscosity and the original viscosity of the flow field is established,and the viscosity term in the turbulence model is modified.This method proves to be able to effectively improve the intensity of small-scale shedding vortexes at the far end of the flow field under the condition of sparse grid.The error between the simulation results and the results obtained by using fine mesh is greatly reduced,the calculation time is shortened,and the high-precision and efficient simulation of the flow field is realized.
基金supported by the Science Council and Top University of NCKU(Grant Nos .NSC96-2221-E-127-006-MY3 and A0162)
文摘In this paper a series of numerical simulations are performed to investigate the vortex shedding mechanism for a solitary wave propagating over a submerged breakwater by use of Reynolds averaged Navier-Stokes （RAINS） model combined with a k-ε model. Flows of different Reynolds numbers up to Re = 1.4 × 10^5 corresponding to varying incident wave heights are considered in which the characteristic fluid velocity is represented by the maximum horizontal velocity above the submerged breakwater. For the verification of the accuracy of the numerical model, the incident waves and the velocity field in the vicinity of the breakwater are compared with experimental data. The result shows that the model is capable of describing vortex shedding for a solitary wave propagating over a rectangular submerged breakwater. Key features of vortex generation, evolution and dissipation are investigated. It is found that the vortex shedding and their evolution due to separated boundary layer over the breakwater are strongly related to the Reynolds number. A considerable number of vortices and complicated vortex pattern are observed as the Reynolds number increases.
文摘本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算涡振时程响应,并通过算例验证了该方法的可行性。与传统的连续模型和随机振动理论计算桥梁涡激响应方法相比,时程计算可以考虑多振型的组合作用,结构非线性等多种影响,具有更大的灵活性。
