In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation...In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.展开更多
生态环境修复方案的可行性论证与修复效果评价是生态环境修复工程的重要内容,对生态环境修复工程的设计及建设具有重要指导意义。目的为确定生态环境修复方案可行性和修复的综合效果,以盘石头水库为例,对该水库生态修复方案进行综合评...生态环境修复方案的可行性论证与修复效果评价是生态环境修复工程的重要内容,对生态环境修复工程的设计及建设具有重要指导意义。目的为确定生态环境修复方案可行性和修复的综合效果,以盘石头水库为例,对该水库生态修复方案进行综合评价研究。方法首先,参照OECD(Organization for Economic Cooperation and Development)模型,构建由生态效益、景观效益、社会效益、维护管理共4个准则层和18个评价子指标组成的盘石头水库生态环境修复方案可行性和修复效果评价体系;其次,通过最优传递矩阵对层次分析法的权重计算进行改进,对构建的评价指标体系进行权重的计算;最后,将改进AHP与模糊综合评价方法相结合,对盘石头水库生态修复方案进行综合评价。结果结果表明,在盘石头水库生态环境修复方案中最重要的准则层指标是生态效益;在选取的18个评价子指标中,物种多样性、观赏价值、改善城市形象和降低灾害这4个指标的权重较大;所评价的鹤壁市盘石头水库生态环境修复方案的修复效果为优,方案可行。结论模糊-改进AHP法为生态环境修复及其方案可行性的评价提供了一种新的、更有效的方法。展开更多
As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canist...As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canister,have grown increasingly complex.However,deficiencies still exist in the current launch modeling theory for BMLRS.In this study,a multi-rigid-flexible-body launch dynamics model coupling the launch platform and rocket was established using the multibody system transfer matrix method and the Newton-Euler formulation.Furthermore,considering the bending of the launch canister,a detection algorithm for slider-guide plane clearance contact was proposed.To quantify the contact force and friction effect between the slider and guide,the contact force model and modified Coulomb model were introduced.Both the modal and launch tests were conducted.Additionally,the modal convergence was verified.By comparing the modal experiments and simulation results,the maximum relative error of the eigenfrequency is 3.29%.thereby verifying the accuracy of the developed BMLRS dynamics model.Furthermore,the launch test validated the proposed plane clearance contact model.Moreover,the study investigated the influence of various model parameters on the dynamic characteristics of BMLRS,including launch canister bending stiffness,slider and guide material,slider-guide clearance,slider length and layout.This analysis of influencing factors provides a foundation for future optimization in BMLRS design.展开更多
文摘In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.
文摘生态环境修复方案的可行性论证与修复效果评价是生态环境修复工程的重要内容,对生态环境修复工程的设计及建设具有重要指导意义。目的为确定生态环境修复方案可行性和修复的综合效果,以盘石头水库为例,对该水库生态修复方案进行综合评价研究。方法首先,参照OECD(Organization for Economic Cooperation and Development)模型,构建由生态效益、景观效益、社会效益、维护管理共4个准则层和18个评价子指标组成的盘石头水库生态环境修复方案可行性和修复效果评价体系;其次,通过最优传递矩阵对层次分析法的权重计算进行改进,对构建的评价指标体系进行权重的计算;最后,将改进AHP与模糊综合评价方法相结合,对盘石头水库生态修复方案进行综合评价。结果结果表明,在盘石头水库生态环境修复方案中最重要的准则层指标是生态效益;在选取的18个评价子指标中,物种多样性、观赏价值、改善城市形象和降低灾害这4个指标的权重较大;所评价的鹤壁市盘石头水库生态环境修复方案的修复效果为优,方案可行。结论模糊-改进AHP法为生态环境修复及其方案可行性的评价提供了一种新的、更有效的方法。
基金supported by National Natural Science Foundation of China(Grant No.92266201).
文摘As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canister,have grown increasingly complex.However,deficiencies still exist in the current launch modeling theory for BMLRS.In this study,a multi-rigid-flexible-body launch dynamics model coupling the launch platform and rocket was established using the multibody system transfer matrix method and the Newton-Euler formulation.Furthermore,considering the bending of the launch canister,a detection algorithm for slider-guide plane clearance contact was proposed.To quantify the contact force and friction effect between the slider and guide,the contact force model and modified Coulomb model were introduced.Both the modal and launch tests were conducted.Additionally,the modal convergence was verified.By comparing the modal experiments and simulation results,the maximum relative error of the eigenfrequency is 3.29%.thereby verifying the accuracy of the developed BMLRS dynamics model.Furthermore,the launch test validated the proposed plane clearance contact model.Moreover,the study investigated the influence of various model parameters on the dynamic characteristics of BMLRS,including launch canister bending stiffness,slider and guide material,slider-guide clearance,slider length and layout.This analysis of influencing factors provides a foundation for future optimization in BMLRS design.
