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悬臂方向对TLV空化抑制效果的影响及其机理

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工程力学 2022年第5期39卷 224-232页

作者：程怀玉季斌龙新平槐文信武汉大学水资源与水电工程科学国家重点实验室武汉430072

该文综合利用实验及数值模拟方法细致研究了悬臂式沟槽叶顶间隙泄漏涡(tip-leakage vortex, TLV)空化抑制器的悬臂凸出方向对抑制TLV空化效果的影响,并对其原因进行了深入讨论。研究表明:相比于原始水翼叶顶处的TLV空化,无论悬臂凸出方... 详细信息

该文综合利用实验及数值模拟方法细致研究了悬臂式沟槽叶顶间隙泄漏涡(tip-leakage vortex, TLV)空化抑制器的悬臂凸出方向对抑制TLV空化效果的影响,并对其原因进行了深入讨论。研究表明:相比于原始水翼叶顶处的TLV空化,无论悬臂凸出方向指向水翼的吸力面还是压力面,悬臂式沟槽TLV空化抑制器在各个间隙大小下均能产生显著的抑制效果。相对而言,当所采用的悬臂凸出方向为压力面时,该装置对TLV空化的抑制效果更为显著,且可更有效地抑制TLV空化体积脉动。测量结果表明:悬臂凸出方向对水翼升、阻力系数影响均很小。数值结果则进一步表明:当采用悬臂凸出方向为指向压力面时,悬臂式沟槽TLV空化抑制器能更好地抑制流体从压力面流向吸力面,干扰TLV的生长,进而可以更加有效地抑制TLV空化的发展。

关键词：空化水翼叶顶间隙泄漏涡流动控制泄漏流

LARGE EDDY SIMULATION OF THE INTERACTION BETWEEN WALL JET AND OFFSET JET

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Journal of Hydrodynamics 2011年第5期23卷 544-553页

作者： LI Zhi-wei huai wen-xin HAN Jie State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China

The interaction between a plane wall jet and a parallel offset jet is studied through the Large Eddy Simulation （LES）. In order to compare with the related experimental data, the offset ratio is set to be 1.0 and the Reynolds number Re is 1.0× 104 with respect to the jet height L and the exit velocity U0. The Finite Volume Method （FVM） with orthogonal-mesh （6.17× 106 nodes） is used to discretize governing equations. The large eddies are obtained directly, while the small eddies are simulated by using the Dynamic Smagorinsky-Lily Model （DSLM） and the Dynamic Kinetic energy Subgrid-scale Model （DKSM）. Comparisons between computational results and experimental data show that the DKSM is especially effective in predicting the mean stream-wise velocity, the half-width of the velocity and the decay of the maximum velocity. The variations of the mean stream-wise velocity and the turbulent intensity at several positions are also obtained, and their distributions agree well with the measurements. The further analysis of dilute characteristics focuses on the tracer concentration, such as the distributions of the concentration （i.e., C / C0 or C / C,,）, the boundary layer thickness 6c and the half-width of the concentration b., the decay of the maximum concentration （ C / Co） along the downstream direction. The turbulence mechanism is also analyzed in some aspects, such as the coherent structure, the correlation function and the Probability Density Function （PDF） of the fluctuating velocity. The results show that the interaction between the two jets is strong near the jet exit and they are fully merged after a certain distance.

关键词： wall jet offset jet dilute characteristic coherent structure

Numerical simulation of air entrainment and suppression in pump sump

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Science China(Technological Sciences) 2016年第12期59卷 1847-1855页

作者： QIAN Zhong Dong WU Peng Fei GUO Zhi Wei huai wen xin State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University

The dynamics of air entrainment and suppression schemes in a pump sump are investigated. Four different turbulence models(standard k-ε model, realizable k-ε model, renormalization group(RNG) k-ε model and shear-stress transport(SST) k-ω model) and the volume of fluid(VOF) multiphase model are employed to simulate the three-dimensional unsteady turbulent flow in a pump sump. The dynamic processes of air entrainment are simulated under conditions of relatively high discharge and low submergence; the mechanism of air entrainment is discussed in detail. Then suppression means for air entrainment is adopted by placing a circular plate on the intake pipe at three different heights. The results show: the position and structure of the free-surface vortices, sidewall-attached vortices, back wall-attached vortices, and floor-attached vortices calculated by SST k-ω turbulence model agree well with the experimental data. The two main contributors for air entrainment are pressure difference and vortex strength. By placing a circular plate in the middle of the intake pipe under water, air entrainment is suppressed because vortex strength is reduced.

关键词：数值模拟抽水蓄能器空气夹带涡流强度湍流模型掺气 k-ε模型

Numerical investigation of flow through vegetated multi-stage compound channel

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Journal of Hydrodynamics 2014年第3期26卷 467-473页

作者：王雯槐文信高猛 State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University

This paper addresses the problem of the renormalization group k turbulence modeling of a vegetated multi-stage compound channel. Results from Micro acoustic Doppler velocimeter（ADV） tests are used with time and spatial averaging（doubleaveraging method） in the analysis of the flow field and the characterization. Comparisons of the mean velocity, the Reynolds stress, and the turbulent energy distribution show the validity of the computational method. The mean velocity profile sees an obvious deceleration in the terraces because of vegetation. Secondary flow exists mainly at the junction of the main channel and the vegetation region on the first terrace. The bed shear stress in the main channel is much greater than that in the terraces. The difference of the bed shear stress between two terraces is insignificant, and the presence of vegetation can effectively reduce the bed shear stress.

关键词： compound channel open channel flow vegetation double-averaging concept bed shear stress

NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

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Journal of Hydrodynamics 2007年第4期19卷 467-472页

作者： QIAN Zhong-dong YANG Jian-dong huai wen-xin State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China

In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show： air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.

关键词： Francis hydraulic turbine air admission pressure pulsation numerical simulation

FLOW STRUCTURE IN PARTIALLY VEGETATED RECTANGULAR CHANNELS

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Journal of Hydrodynamics 2010年第4期22卷 590-597页

作者： CHEN Gang huai wen-xin HAN Jie ZHAO Ming-deng State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China

This article discusses the transverse distributions of the depth averaged velocity and the Reynolds stress in a steady uniform flow in partially vegetated rectangular *** momentum equation is expressed in dimensionless form and solved to obtain the depth averaged *** analytical solution of the velocity in dimensionless form shows that the depth-averaged velocity is determined by gravity and its distribution is mainly determined by the frictions due to water or *** analytical solution of the Reynolds stress is also obtained.A relationship between the second flow and the inertia is established and it is assumed that the former is proportional to the square of the depth averaged *** Acoustic Doppler Velocimeter（Micro ADV） was used to measure the steady uniform flow with emergent artificial rigid *** between the measured data and the computed results show that our method does well in predicting the transverse distributions of the stream-wise velocity and the Reynolds stress in rectangular channels with partially vegetations.

关键词： drag fbrce partially vegetated channel secondary currents velocity distribution

LARGE EDDY SIMULATION OF OPEN CHANNEL FLOWS WITH NONSUBMERGED VEGETATION

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Journal of Hydrodynamics 2011年第2期23卷 258-264页

作者： huai wen-xin WU Zhen-lei QIAN Zhong-dong GENG Chuan State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China

Results of several Large Eddy Simulations （LES） this article. It is shown that the vegetation can make the flow of open channel flows with non-submerged vegetation are presented in structure in the mainstream direction uniform for both supercritical and subcritical flows. For subcritical flows, the LES results of the ensemble-average of time-averaged velocity distributions at four vertical sections around a single plant are in good agreement with measurements. The velocity sees double peaks at the upper and lower positions of flows. For supercritical flows, the ensemble-average velocities see some discrepancy between LES and measurement results. Some secondary flow eddies appear near the single plant, and they just locate in the positions of the double peaks in stream-wise velocity profiles. It is also found that the vegetation drag coefficient deceases as the Froude number increases.

关键词： non-submerged sub/supercritical flow peak value Large Eddy Simulation (LES) secondary flow drag coefficient

Theoretical understanding of correlation between magnetic phase transition and the superconducting dome in high-Tc cuprates

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 167-173页

作者： Chen Zhang Cai-xin Zhang Su-huai Wei Haiqing Lin Hui-Xiong Deng State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Beijing Computational Science Research Center Beijing 100193China

Many issues concerning the origin of high-temperature superconductivity(HTS)are still under *** example,how the magnetic order varies with doping and its relationship with the superconducting temperature(Tc);and why Tcalways peaks near the quantum critical *** this paper,taking hole-doped La_(2)CuO_(4)as a classical example,we employ the first-principles band structure and total energy calculations with Monte Carlo simulations to explore how the symmetry-breaking magnetic ground state evolves with hole doping and the origin of a dome-shaped superconductivity region in the phase *** demonstrate that the local antiferromagnetic order and doping play key roles in determining the electron-phonon coupling,thus ***,the La_(2)CuO_(4)possesses a checkerboard local antiferromagnetic ground *** the hole doping increases,Tcincreases with the enhanced electron-phonon coupling *** as the doping increases further,the strength of the antiferromagnetic interaction weakens and spin fluctuation *** the critical doping level,a magnetic phase transition occurs that reduces the local antiferromagnetism-assisted electron-phonon coupling,thus diminishing the *** superconductivity disappears in the heavily overdoped region when the ferromagnetic order *** observations could account for why cuprates have a dome-shaped superconductivity region in the phase *** study,thus,contributes to a fundamental understanding of the correlation between doping,local magnetic order,and superconductivity of HTS.

关键词： high-temperature superconductivity antiferromagnetic order electron-phonon coupling doping effect cuprates

CURVED OPEN CHANNEL FLOW ON VEGETATION ROUGHENED INNER BANK

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Journal of Hydrodynamics 2012年第1期24卷 124-129页

作者： huai wen-xin LI Cheng-guang ZENG Yu-hong QIAN Zhong-dong YANG Zhong-hua State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China

A RNG numerical model together with a laboratory measurement with Micro ADV are adopted to investigate the flow through a 180o curved open channel（a 4 m straight inflow section,a 180o curved section,and a 4m straight outflow section）partially covered with rigid vegetations on its inner *** the combined action of the vegetation and the bend flow,the flow structure is *** stream-wise velocities in the vegetation region are much smaller than those in the non-vegetation region due to the retardation caused by the *** the same reason,no clear circulation is found in the vegetated region,while in the non-vegetation region,a slight counter-rotating circulation is found near the outer bank at both 90o and downstream curved cross-sections.A comparison between the numerical prediction and the laboratory measurement shows that the RNG model can well predict the flow structure of the bend flow with ***,the shear stress is analyzed based on the numerical *** much smaller value in the inner vegetated region indicates that the vegetation can effectively protect the river bank from scouring and erosion,in other words,the sediment is more likely to be deposited in the vegetation region.

关键词： RNG numerical model non-submerged rigid vegetation bend flow stream-wise velocities shear stress