Rational determination and reduction of local energy loss of oil flow at pipe junctions are of important significance to improve hydraulic pipeline＇s work efficiency, especially for complex hydraulic pipeline connect...Rational determination and reduction of local energy loss of oil flow at pipe junctions are of important significance to improve hydraulic pipeline＇s work efficiency, especially for complex hydraulic pipeline connected by isodiametric T-type ducts with sharp comers to get combined and divided flow. From this point of view, the formulae of resistance loss for combined flow and divided flow through isodiametric T-type duct with sharp comers as well as the correlations of resistance loss coefficients in the branches of the duct are derived using energy method. On this basis, resistance characteristics of hydraulic oil in the duct are obtained by numerical simulation of different flow modes, which are commonly applied in hydraulic pipelines, using computational fluid dynamics （CFD） method, and the reasons for the resistance loss are analyzed based on the pressure change mechanism in the flow field. A part of simulation results was validated with the reference data. The research shows that for combined flows the resistance loss of symmetrical is lower than that of unsymmetrical to obtain low speed in common branch, but to gain high speed is quite the contrary, for divided flows, the symmetrical is always a reasonable choice to reduce resistance loss. These conclusions can be applied to optimize the design of hydraulic pipeline.展开更多
Computational fluid dynamics(CFD)was used in conjunction with BP neural network to study theflow resistance characteristic of the combination-channel inside hydraulic manifold block(HMB).The in-put parameters of the c...Computational fluid dynamics(CFD)was used in conjunction with BP neural network to study theflow resistance characteristic of the combination-channel inside hydraulic manifold block(HMB).The in-put parameters of the combination-channel model were confirmed to have effect on the pressure-drop bythe numerical method,and a BP neural network model was accordingly constructed to predict the channelpressure-drops.The flow resistance characteristic curves of various channels were achieved,and a perfor-mance parameter was given to evaluate the through-flow characteristic of the channel according to thecurves.The predictions are' in agreement with the numerical computation,indicating that the method canbe utilized to accurately determine the flow characteristic of the combination channel with high efficiency.展开更多
Qi, blood and the meridians are fundamental concepts in Chinese medicine（CM）, which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to d...Qi, blood and the meridians are fundamental concepts in Chinese medicine（CM）, which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.展开更多
ISO 12922-2012是目前最完整的难燃液压液技术规格,分为含水型和合成酯型2大类,包含HFAE、HFAS、HFB、HFC、HFDR和HFDU 6个品种,广泛应用于钢铁、化工、电力、船舶、煤矿等行业。文章介绍了6种难燃液压液的范围及用途、规范性引用文件...ISO 12922-2012是目前最完整的难燃液压液技术规格,分为含水型和合成酯型2大类,包含HFAE、HFAS、HFB、HFC、HFDR和HFDU 6个品种,广泛应用于钢铁、化工、电力、船舶、煤矿等行业。文章介绍了6种难燃液压液的范围及用途、规范性引用文件、技术要求及技术现状。展开更多
选用适合调压室流动的三维可视化k-ε双方程湍流模型以及考虑边壁粗糙度的壁函数,采用一阶精度及S IM PLE算法,以FLUENT流体计算软件为计算平台,对抽水蓄能电站调压室流场进行了数值模拟。通过对比和分析表明,在分流、合流两种流态下利...选用适合调压室流动的三维可视化k-ε双方程湍流模型以及考虑边壁粗糙度的壁函数,采用一阶精度及S IM PLE算法,以FLUENT流体计算软件为计算平台,对抽水蓄能电站调压室流场进行了数值模拟。通过对比和分析表明,在分流、合流两种流态下利用计算流体动力学CFD方法计算得到的水头损失系数值与常规物理模型试验得到的结果,在规律和数值上基本吻合,表明计算流体动力学可以应用于抽水蓄能电站调压室的优化设计中。展开更多
基金supported by Hebei Provincial Natural Science Foundation of China (Grant No. 503292)
文摘Rational determination and reduction of local energy loss of oil flow at pipe junctions are of important significance to improve hydraulic pipeline＇s work efficiency, especially for complex hydraulic pipeline connected by isodiametric T-type ducts with sharp comers to get combined and divided flow. From this point of view, the formulae of resistance loss for combined flow and divided flow through isodiametric T-type duct with sharp comers as well as the correlations of resistance loss coefficients in the branches of the duct are derived using energy method. On this basis, resistance characteristics of hydraulic oil in the duct are obtained by numerical simulation of different flow modes, which are commonly applied in hydraulic pipelines, using computational fluid dynamics （CFD） method, and the reasons for the resistance loss are analyzed based on the pressure change mechanism in the flow field. A part of simulation results was validated with the reference data. The research shows that for combined flows the resistance loss of symmetrical is lower than that of unsymmetrical to obtain low speed in common branch, but to gain high speed is quite the contrary, for divided flows, the symmetrical is always a reasonable choice to reduce resistance loss. These conclusions can be applied to optimize the design of hydraulic pipeline.
基金the National Natural Science Foundation of China(No.50375023)
文摘Computational fluid dynamics(CFD)was used in conjunction with BP neural network to study theflow resistance characteristic of the combination-channel inside hydraulic manifold block(HMB).The in-put parameters of the combination-channel model were confirmed to have effect on the pressure-drop bythe numerical method,and a BP neural network model was accordingly constructed to predict the channelpressure-drops.The flow resistance characteristic curves of various channels were achieved,and a perfor-mance parameter was given to evaluate the through-flow characteristic of the channel according to thecurves.The predictions are' in agreement with the numerical computation,indicating that the method canbe utilized to accurately determine the flow characteristic of the combination channel with high efficiency.
基金Supported by the National Basic Research Program of China(973 Program,No.2015CB554502)ENN Group Research Project(No.20160013)
文摘Qi, blood and the meridians are fundamental concepts in Chinese medicine（CM）, which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.
文摘选用适合调压室流动的三维可视化k-ε双方程湍流模型以及考虑边壁粗糙度的壁函数,采用一阶精度及S IM PLE算法,以FLUENT流体计算软件为计算平台,对抽水蓄能电站调压室流场进行了数值模拟。通过对比和分析表明,在分流、合流两种流态下利用计算流体动力学CFD方法计算得到的水头损失系数值与常规物理模型试验得到的结果,在规律和数值上基本吻合,表明计算流体动力学可以应用于抽水蓄能电站调压室的优化设计中。
