Design parameter optimization method for a prestressed steel structure driven by multi-factor coupling

To achieve efficient structural design,it is crucial to reduce the cost of materials while ensuring structural safety.This study proposes an optimization method for design parameters(DPs)in a prestressed steel structure driven by multi-factor coupling.To accomplish this,a numerical proxy model of prestressed steel structures is established with integration of DPs and mechanical parameters(MPs).A data association-parameter analysis-optimization selection system is established.A correlation between DPs and MPs is established using a back propagation(BP)neural network.This correlation provides samples for parameter analysis and optimization selection.MPs are used to characterize the safety of the structure.Based on the safety grade analysis,the key DPs that affect the mechanical properties of the structure are obtained.A mapping function is created to match the MPs and the key DPs.The optimal structural DPs are obtained by setting structural materials as the optimization objective and safety energy as the constraint condition.The theoretical model is applied to an 80-m-span gymnasium and verified with a scale test physical model.The MPs obtained using the proposed method are in good agreement with the experimental results.Compared with the traditional design method,the design cycle can be shortened by more than 90%.Driven by the optimal selection method,a saving of more than 20% can be achieved through reduction of structural material quantities.Moreover,the cross-sectional dimensions of radial cables have a substantial influence on vertical displacement.The initial tension and cross-sectional size of the upper radial cable exhibit the most pronounced impact on the stress distribution in that cable.The initial tension and cross-sectional size of the lower radial cable hold the greatest sway over the stress distribution in that cable.

Investigation on the relationship between hydraulic loss and vortex evolution in pump mode of a pump-turbine

Hydraulic loss and vorticity are two most common methods in analyzing the flow characteristics in hydro-machine,i.e.,centrifugal pump,Francis turbine,etc.While the relationship and correlation between hydraulic loss and vortex evolution are not uncovered yet.In this study,hydraulic loss is regarded as the combination of dissipation effect and transportation effect in flow domains.Meanwhile,vorticityωcan be decomposed into two parts,namely the Liutex partω_(R),the shear partωs,of whichω_(R)is regarded as the third-generation vortex identification method for its precise and rigorous definition of local rigid rotation part of fluid.Based on the dimensional analysis,two new physical quantities related to vorticity(ω,ω_(R)andωS),namely enstrophyΩ,vorticity transport intensity T are adopted to express the energy characteristic in vortex evolution process.Finally,operating points at pump mode of an ultra-high head reversible pump-turbine are selected as the research object and the numerical results calculated using SST k-ωturbulence model are consistent well with the experimental data.Pearson correlation coefficient is adopted to evaluate the correlation between hydraulic loss and vortex evolution in main flow regions.Results show that apart from the spiral casing domain,the enstrophy of shear partΩs has very strong correlation with dissipation effect and Liutex transport intensity TR has stronger correlation with transportation effect when compared with other forms of vorticity.The correlation between Liutex transport intensity TR and transportation effect is strong in stay/guide vanes(SGVs)while reduce to medium level in runner and draft tube domains.In spiral casing domain,all forms of vorticity show weak or very weak correlation with transportation effect.Based on the proposed method,we believe that the relationship and correlation between hydraulic loss and vortex evolution in other hydraulic machineries can also be clearly investigated.

给定活动导叶开口水泵水轮机模型泵工况驼峰现象流动分析（英文）

目的:探索水泵水轮机泵工况在超负荷工况(1.24φBEP)、最优工况(1.00φBEP)、靠近最优工况(0.90φBEP)、驼峰区工况(0.65φBEP)以及低负荷工况(0.45φBEP)的流动特性,期望获得流动特性变化规律,揭示驼峰特性形成机理。方法:对某一水泵水轮机模型,采用剪切压力传输(SST)k-ω湍流模型进行三维定常数值模拟,在实验验证的基础上:1.在曲面坐标系中,分析由叶片形状所引起的各个工况叶片进出口边在周向和叶片方向上的分布规律;2.运用经典欧拉理论分析叶片进出口边液流角变化对各个工况的欧拉水头的影响;3.通过水力损失分析,获得不同部件各个工况损失变化规律。结论:1.转轮叶片进出水边的液流角随着叶片方向在不同流量工况分布下具有明显差异,导致转轮流道不同程度流动分离;2.运用经典欧拉理论得出驼峰区工况点出口角液流的减小与入口液流的增加是驼峰特性产生的主要原因之一;3.通过损失分析,确定泵工况损失主要在转轮和双列叶栅中,得出转轮部分损失是驼峰特性形成的主要原因之一;4.综合分析,驼峰特性是由该工况欧拉动量的减小和转轮部分损失的增加共同作用的结果。