In this paper both Eulerian and Lagrangian approaches are used on the numericalcomputations of dilute gas-solid two-phase flows. In Eulerian approach the gas flow field in atwo-dimensional tunnel is computed by a gene...In this paper both Eulerian and Lagrangian approaches are used on the numericalcomputations of dilute gas-solid two-phase flows. In Eulerian approach the gas flow field in atwo-dimensional tunnel is computed by a general-used software. From this result the particletrajectory is computed by the model of one-way coupling using the knocking relation obtainedfrom the experiments. The computed result shows good agreement with that produced fromexperimental measurement. In addition, in order to consider the coupling effect between thetwo-phase, a two-way coupling model is also used to compute the particle trajectory, andproduced some useful conclusion. The presented computing program can be used to predictthe trajectory of solid particle in dilute two-phase flow.展开更多
A dam-reservoir system subjected to an earthquake is a nonlinear system, because the fluid equations are always nonlinear regardless of the linear or nonlinear model used for the dam body. Therefore, transient analysi...A dam-reservoir system subjected to an earthquake is a nonlinear system, because the fluid equations are always nonlinear regardless of the linear or nonlinear model used for the dam body. Therefore, transient analysis is necessary. In this study, dam-reservoir interaction during earthquake excitation was modeled by utilizing coupled finite element equations based on the Eulerian approach. Direct computing of the one-way coupling technique was used to solve the coupled equations. This technique is based on a simple assumption that the fluid hydrodynamic pressure is applied to the dam body while the deformation of the dam has no influence on the water field. Seismic response analysis of the Sonla concrete gravity dam constructed in Sonla Province, Vietnam was carried out as a verification example. The results of the methodology introduced are in close agreement with results of the iterative method and the solution procedure is found to be less time-consuming than that of the iterative method. This method is very convenient and can be easily implemented in finite element programs with fluid-structure interaction modules.展开更多
柴油机功率的不断提升,排气温度也相应升高,排气歧管须承受更高的热负荷,从而可能导致其热机械疲劳失效。在设计初期阶段可通过计算机辅助工程(CAE)分析工具执行一系列虚拟模型仿真验算以验证设计方案的可行性和潜在风险,而非花费高额...柴油机功率的不断提升,排气温度也相应升高,排气歧管须承受更高的热负荷,从而可能导致其热机械疲劳失效。在设计初期阶段可通过计算机辅助工程(CAE)分析工具执行一系列虚拟模型仿真验算以验证设计方案的可行性和潜在风险,而非花费高额成本和大量时间针对实际样品进行测试验证。采用瞬态传热计算流体动力学(Computational Fluid Dynamics,CFD)分析和实体壁面温度相映射的方法模拟排气流经排气歧管时流动分离情况,经CFD和有限元分析(Finite Element Analysis,FEA)之间的耦合迭代后,根据热机械计算结果,即温度场、应力和塑性应变参数监测歧管结构设计缺陷,然后选择合适的材料属性和评估关键位置潜在开裂风险,最后依据各方案计算结果制造出排气歧管样件,在试验台架上进行整机耐久性测试,试验中未出现开裂失效,研究结果表明采用热机械疲劳分析方法可有效预测排气歧管疲劳潜在失效并为结构设计变更提供指导。展开更多
Tropical cyclones are devastating hazards and have been a major problem for the coastal population of B angladesh.Among the advancements in atmospheric and oceanic prediction,accurate forecasting of storm surges is of...Tropical cyclones are devastating hazards and have been a major problem for the coastal population of B angladesh.Among the advancements in atmospheric and oceanic prediction,accurate forecasting of storm surges is of specific interest due to their great potential to inflict loss of life and property.For decades,the numerical model based storm surge prediction systems have been an important tool to reduce the loss of human lives and property damage.In order to improve the accuracy in predicting storm surge and coastal inundation,recent model development efforts tended to include more modeling components,such as meteorology model and surface wave model in storm surge modeling.In this study,we used the outputs of an atmospheric model to force the ocean model for simulating storm surges in the Bay of Bengal with particular focus on the Bangladesh coast.The ability of the modeling system was investigated simulating water levels in the Bangladesh coast of two tropical cyclones Sidr(2007)and Aila(2009).The effectiveness of the model was verified through comparing the obtained computational outputs against tide gauge data.The cyclone tracks and intensities reproduced by the atmospheric model were reasonable,though the model had a tendency to overestimate the cyclone intensity during peaks and also close to coast.The water levels are reproduced fairly well by the ocean model,although errors still exist.The root mean square errors in water level at different gauges range from 0.277 to 0.419 m with coefficient of correlation(R^2)between 0.64 and 0.97 in case of Sidr and0.209-0.581 m with R^20.62 to 0.98 for Aila.The overall coupled modeling system is found to be useful with reasonable accuracy and precision,though there are spaces for improvement.Higher-resolution modeling approaches are recommended to gain more skills.展开更多
This study proposed a partitioned method to analyze maneuvering of insects during flapping flight.This method decomposed the insect flapping flight into wing and body subsystems and then coupled them via boundary cond...This study proposed a partitioned method to analyze maneuvering of insects during flapping flight.This method decomposed the insect flapping flight into wing and body subsystems and then coupled them via boundary conditions imposed on the wing’s base using one-way coupling.In the wing subsystem,the strong coupling of the flexible wings and surrounding fluid was accurately analyzed using the finite element method to obtain the thrust forces acting on the insect’s body.The resulting thrust forces were passed from the wing subsystem to the body subsystem,and then rigid body motion was analyzed in the body subsystem.The rolling,yawing,and pitching motions were simulated using the proposed method as follows:In the rolling simulation,the difference of the stroke angle between the right and left wings caused a roll torque.In the yawing simulation,the initial feathering angle in the right wing only caused a yaw torque.In the pitching simulation,the difference between the front-and back-stroke angles in both the right and left wings caused a pitch torque.All three torques generated maneuvering motion comparable with that obtained in actual observations of insect flight.These results demonstrate that the proposed method can adequately simulate the fundamental maneuvers of insect flapping flight.In the present simulations,the maneuvering mechanisms were investigated at the governing equation level,which might be difficult using other approaches.Therefore,the proposed method will contribute to revealing the underlying insect flight mechanisms.展开更多
文摘In this paper both Eulerian and Lagrangian approaches are used on the numericalcomputations of dilute gas-solid two-phase flows. In Eulerian approach the gas flow field in atwo-dimensional tunnel is computed by a general-used software. From this result the particletrajectory is computed by the model of one-way coupling using the knocking relation obtainedfrom the experiments. The computed result shows good agreement with that produced fromexperimental measurement. In addition, in order to consider the coupling effect between thetwo-phase, a two-way coupling model is also used to compute the particle trajectory, andproduced some useful conclusion. The presented computing program can be used to predictthe trajectory of solid particle in dilute two-phase flow.
文摘A dam-reservoir system subjected to an earthquake is a nonlinear system, because the fluid equations are always nonlinear regardless of the linear or nonlinear model used for the dam body. Therefore, transient analysis is necessary. In this study, dam-reservoir interaction during earthquake excitation was modeled by utilizing coupled finite element equations based on the Eulerian approach. Direct computing of the one-way coupling technique was used to solve the coupled equations. This technique is based on a simple assumption that the fluid hydrodynamic pressure is applied to the dam body while the deformation of the dam has no influence on the water field. Seismic response analysis of the Sonla concrete gravity dam constructed in Sonla Province, Vietnam was carried out as a verification example. The results of the methodology introduced are in close agreement with results of the iterative method and the solution procedure is found to be less time-consuming than that of the iterative method. This method is very convenient and can be easily implemented in finite element programs with fluid-structure interaction modules.
文摘柴油机功率的不断提升,排气温度也相应升高,排气歧管须承受更高的热负荷,从而可能导致其热机械疲劳失效。在设计初期阶段可通过计算机辅助工程(CAE)分析工具执行一系列虚拟模型仿真验算以验证设计方案的可行性和潜在风险,而非花费高额成本和大量时间针对实际样品进行测试验证。采用瞬态传热计算流体动力学(Computational Fluid Dynamics,CFD)分析和实体壁面温度相映射的方法模拟排气流经排气歧管时流动分离情况,经CFD和有限元分析(Finite Element Analysis,FEA)之间的耦合迭代后,根据热机械计算结果,即温度场、应力和塑性应变参数监测歧管结构设计缺陷,然后选择合适的材料属性和评估关键位置潜在开裂风险,最后依据各方案计算结果制造出排气歧管样件,在试验台架上进行整机耐久性测试,试验中未出现开裂失效,研究结果表明采用热机械疲劳分析方法可有效预测排气歧管疲劳潜在失效并为结构设计变更提供指导。
文摘Tropical cyclones are devastating hazards and have been a major problem for the coastal population of B angladesh.Among the advancements in atmospheric and oceanic prediction,accurate forecasting of storm surges is of specific interest due to their great potential to inflict loss of life and property.For decades,the numerical model based storm surge prediction systems have been an important tool to reduce the loss of human lives and property damage.In order to improve the accuracy in predicting storm surge and coastal inundation,recent model development efforts tended to include more modeling components,such as meteorology model and surface wave model in storm surge modeling.In this study,we used the outputs of an atmospheric model to force the ocean model for simulating storm surges in the Bay of Bengal with particular focus on the Bangladesh coast.The ability of the modeling system was investigated simulating water levels in the Bangladesh coast of two tropical cyclones Sidr(2007)and Aila(2009).The effectiveness of the model was verified through comparing the obtained computational outputs against tide gauge data.The cyclone tracks and intensities reproduced by the atmospheric model were reasonable,though the model had a tendency to overestimate the cyclone intensity during peaks and also close to coast.The water levels are reproduced fairly well by the ocean model,although errors still exist.The root mean square errors in water level at different gauges range from 0.277 to 0.419 m with coefficient of correlation(R^2)between 0.64 and 0.97 in case of Sidr and0.209-0.581 m with R^20.62 to 0.98 for Aila.The overall coupled modeling system is found to be useful with reasonable accuracy and precision,though there are spaces for improvement.Higher-resolution modeling approaches are recommended to gain more skills.
文摘This study proposed a partitioned method to analyze maneuvering of insects during flapping flight.This method decomposed the insect flapping flight into wing and body subsystems and then coupled them via boundary conditions imposed on the wing’s base using one-way coupling.In the wing subsystem,the strong coupling of the flexible wings and surrounding fluid was accurately analyzed using the finite element method to obtain the thrust forces acting on the insect’s body.The resulting thrust forces were passed from the wing subsystem to the body subsystem,and then rigid body motion was analyzed in the body subsystem.The rolling,yawing,and pitching motions were simulated using the proposed method as follows:In the rolling simulation,the difference of the stroke angle between the right and left wings caused a roll torque.In the yawing simulation,the initial feathering angle in the right wing only caused a yaw torque.In the pitching simulation,the difference between the front-and back-stroke angles in both the right and left wings caused a pitch torque.All three torques generated maneuvering motion comparable with that obtained in actual observations of insect flight.These results demonstrate that the proposed method can adequately simulate the fundamental maneuvers of insect flapping flight.In the present simulations,the maneuvering mechanisms were investigated at the governing equation level,which might be difficult using other approaches.Therefore,the proposed method will contribute to revealing the underlying insect flight mechanisms.
