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Computation method and control strategy of rotating separation flows in hydraulic machinery

Journal of Hydrodynamics 2022年第6期34卷 1006-1020页

作者： Chao-yue wang fu-jun wang Hao wang Hao-ru Zhao Zhi-feng Yao Ruo-fu Xiao College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing100083China Department of Energy and Power Engineering Tsinghua UniversityBeijing100084China

Rotating separation flow(RSF)in hydraulic machinery is characterized by the large flow separations and complex vortical structures induced by the effects of strong rotation,large curvature and multiple wall surfaces,and conducting efficient engineering computation and putting forward effective control strategy for the RSF are important topics in the inner flow theory.To meet these engineering requirements,the studies on computational method and control strategy of the RSF are conducted in this paper.In terms of the computational method,the time-scale-driven(TSD)hybrid unsteady Reynolds-averaged Navier-Stokes/large eddy simulation(URANS/LES)modelling strategy is clarified,and an adaptive TSD hybrid model is established based on the RSF characteristics in hydraulic machinery,thereby avoiding the problem of non-monotonic grid convergence and improving the robustness.Besides,a novel vortex-feature-driven idea suitable for the RSF is further developed inspired by it.In terms of the control strategy,the secondary flow generation mechanism in a rotor domain is revealed,and the relationship between natural secondary flows and blade loading distributions is grasped.On the basis of it,an active control strategy with general significance is proposed,and a general alternate loading technique(GALT)is established.Both aspects can provide generalized paradigms with expandable potential,which are of benefit to the efficient computation and effective control of the RSF in hydraulic machinery.

关键词： Rotating separation flow hydraulic machinery engineering computation turbulence model flow control blade loading

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Deflection of cavitation bubble near the rigid wall with a gas-containing hole

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Journal of Hydrodynamics 2023年第2期35卷 330-337页

作者： Yu-rong Sun Qiang Zhong Zhi-feng Yao Dan Zi Ruo-fu Xiao fu-jun wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing100083China

The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affect the direction of the microjet.The motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing hole.Evolutions of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the boundary.It focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the results.It was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation period.In addition,it can control the deflection of the bubble.

关键词： Cavitation bubble bubble migration deflection angle gas-containing hole

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Non-spherical symmetry development of underwater shock waves created by laser-induced breakdown

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Journal of Hydrodynamics 2023年第1期35卷 76-82页

作者： Ying-xue wang Di-xi Han Jian-hua Liu Qiang Zhong Zhi-feng Yao Ruo-fu Xiao fu-jun wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China China Ship Scientific Research Centre Wuxi214082China Taihu Laboratory of Deepsea Technological Science Wuxi214082China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing100083China

As a controllable alternative to cavitation collapse-induced shock waves,numerous cavitation studies on laser-induced breakdown have been carried out in hydromechanics.When the laser focusing region is not spherical,the shock waves caused by laser breakdown also exhibit non-spherical symmetry propagation.Recently,some researchers have proposed the linear superposition theory based on the far field measurement data to explain this asymmetry,assuming that it is essentially the linear superposition of multiple wave fronts caused by multiple points of laser-induced breakdown that leads to the asymmetric propagation of shock waves.In this study,measurements of shock wave propagation processes with different breakdown energies are carried out based on a nanosecond resolution photogrammetry system,and the propagation velocities of shock waves in different directions are directly measured using a double exposure technique on a single frame.In the experiment,the velocity of the shock wave at the beginning of the breakdown was measured up to nearly 4000 m/s.The early shock wave front was ellipsoidal,and the propagation velocity in the laser incident direction was generally slower than that in the perpendicular direction,decaying to the speed of sound in water within 1000 ns after the breakdown,and the wave front gradually approached to a circle.The variability of the shock wave front pressure ratio in the laser propagation direction and the vertical direction implies that the linear superposition theory applicable to the far field is not applicable to the near field.There may be more complex mechanism for the near-field shock wave propagation process.

关键词： Underwater shock wave non-spherical symmetry velocity decay linear superposition laser breakdown

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A modified VLES model for simulation of rotating separation flow in axial flow rotating machinery

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Journal of Hydrodynamics 2022年第4期34卷 570-584页

作者： Hao-ru Zhao fu-jun wang Chao-yue wang Chang-liang Ye Zhi-feng Yao Qiang Zhong College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing 100083China College of Energy and Electrical Engineering Hohai UniversityNanjing 211100China

The internal flow in an axial flow rotating machinery is affected by the rotating characteristics, often accompanied by a strong rotating separation under small flow conditions. At present, the very large eddy simulation (VLES) model commonly used for the separation flow simulation still has certain limitations in simulating such rotating separation flow: (1) The Reynolds stress level is overestimated in the near-wall region. (2) The influence of the rotating effect cannot be effectively considered. The above two limitations affect the simulation accuracy of the VLES model for the rotating separation flow under small flow conditions in the axial flow rotating machinery. The objective of this paper is to provide a new hybrid unsteady Reynolds average Navier-Stokes/large eddy simulation (URANS/LES) model suitable for the simulation of the rotating separation flow in an axial flow rotating machinery. Compared with the original VLES method, the modifications are as follows: (1) A Reynolds stress damping function in the near-wall region is introduced to reduce the overestimation of the Reynolds stress caused by the near-wall Reynolds average Navier-Stokes (RANS) behavior of the VLES model. (2) A control function driven by the vortex is introduced to reflect the influence of the rotating effect. Three typical cases are used to verify the calculation accuracy of the modified model. It is shown that the modified model can capture more turbulent vortices based on the URANS grids, and the prediction accuracy of the rotating separation flow is effectively improved. Compared with the original VLES model, the modified model can accurately predict the head change in the hump region of the axial flow pump.

关键词： Axial flow rotating machinery rotating separation flow hybrid unsteady Reynolds average Navier-Stokes/large eddy simulation(URANS/LES)model very large eddy simulation(VLES)model

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Investigations of the dynamical behaviors of a millimeter-scale cavitation bubble near the rigid wall

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Journal of Hydrodynamics 2023年第6期35卷 1064-1076页

作者： Dan Zi Dong-qiao He Zhi-feng Yao fu-jun wang Qiang Zhong Pin Lyu College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing100083China Yichang Testing Technology Research Institute Yichang443000China

The collapse of the cavitation bubble near the rigid wall emits shock waves and creates micro-jet,causing cavitation damage and operation instability of the hydraulic machinery.In this paper,the millimeter-scale bubble near the rigid wall was investigated experimentally and numerically with the help of a laser photogrammetry system with nanosecond-micron space-time resolution and the open source package OpenFOAM-2212.The morphological characteristics of the bubble during its growth phase,collapse phase and rebound phase were observed by experiment and numerical simulation,and characteristics of the accompanying phenomena including the shock wave propagation and micro-jet evolution were well elucidated.The numerical results agree well with the experimental data.The bubble starts from a tiny small size with high internal pressure and expands into a sphere with a radius of 1.07 mm forγ=d/R_(max)=1.78.The bubble collapses into a heart shape and moves towards to the rigid wall during its collapse phase,resulting in a higher pressure load for the rigid wall in the second collapse.The maximum pressure of the shock wave of the first bubble collapse phase reaches 5.4 MPa,and the velocity of the micro-jet reaches approximately 100 m/s.This study enriches the existing experimental and numerical results of the dynamics of the near-wall cavitation bubble.

关键词： Cavitation bubble collapse shock wave micro jet the rigid wall

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Numerical investigation of filling transients in small-scale pipelines with submerged outlet

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Journal of Hydrodynamics 2019年第1期31卷 145-151页

作者： Ling wang fu-jun wang Jing Huang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing 100083China Zhuzhou Southern Valve Co. Ltd Zhuzhou 412007China

An elastic model that combines the dead-end and the orifice at the downstream end is proposed in order to study the hydraulic transients during the rapid filling in small-scale pipelines with submerged outlet.In this model,the unsteady water flow is solved by the method of characteristics,the water-air interface is traced by a shock fitting method,and the air phase is controlled by the polytropic law.The model is validated by a filling test in a pipeline with orifice.Then the proposed model is applied to the filling transient analysis in a small-scale pipeline with submerged outlet.Finally,the effects of the submerged depth of the downstream reservoir on the filling transients are analyzed.This model provides a reasonable approximation of the submerged outlet boundary condition in small-scale pipelines.

关键词： Small-scale pipelines rapid filling submerged outlet elastic model hydraulic transients

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Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump

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Chinese Journal of Mechanical Engineering 2018年第1期31卷 198-211页

作者： Da-Chun fu fu-jun wang Pei-Jian Zhou Ruo-fu Xiao Zhi-Feng Yao College of Water Resources and Civil Engineering China Agricultural University Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural University College of Mechanical Engineering Zhejiang University of Technology

Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.

关键词： Double-suction centrifugal pump Impeller stagger angle Pressure fluctuation Frequency spectra analysis

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A novel Omega-driven dynamic PANS model

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Journal of Hydrodynamics 2020年第4期32卷 710-716页

作者： Chao-yue wang fu-jun wang Ben-hong wang Yuan Tang Hao-ru Zhao College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing 100083China

A novel Omega(Ω)-driven dynamic partially-averaged Navier-Stokes(PANS)model is proposed in this paper.The ratio of the modeled-to-total turbulent kinetic energies fk is dynamically adjusted by the rigid vorticity ratio(the ratio of the rigid vorticity to the total vorticity),the key parameter of the Ω vortex identification method.Three classical flow cases with rotation and curvature are used to test the model.The results show that the turbulent viscosity is effectively adjusted by the new dynamic fk and the LES-like mode is activated,which can help the revelation of more turbulence information and improve the prediction accuracy.The new PANS model does not contain any explicit dependency on the grid size and enjoys good adaptability to the flow fields,and can be used for efficient engineering computations of the turbulent flows in the hydraulic machinery.

关键词： Dynamic partially-averaged Navier-Stokes(PANS) turbulence model Omega engineering computations

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Numerical studies of the hydrodynamic damping of a vibrating hydrofoil in torsional mode

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Journal of Hydrodynamics 2021年第2期33卷 347-360页

作者： Yong-shun Zeng Zhi-feng Yao Biao Huang fu-jun wang Qin Wu Ruo-fu Xiao Guo-yu wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing 100083China School of Mechanical and Vehicular Engineering Beijing Institute of TechnologyBeijing 100081China

The vortex-induced vibration may lead to a premature failure of hydraulic mechanical systems,especially under the resonance condition in the torsional mode.To predict the structural fatigue life,a careful consideration of the dynamic response to the hydraulic excitations is essential in the design phase.This study focuses on the numerical investigation of the relationship between the flow velocity,the added mass and the hydrodynamic damping,particularly,with respect to a Donaldson-type hydrofoil,vibrating in the first torsional mode.A two-way fluid-structure interaction(FSI)method is used to predict above two parameters.The flow velocity is in the range of 0 m/s-20m/s.To evaluate the hydrodynamic damping ratio,an identification method is proposed,based on a modified version of the logarithmic decay method.The relative deviations of the simulated natural frequencies and hydrodynamic damping ratios as compared with the experimental data for the first torsional modes,are within 8.1%and 16.6%,respectively.The analysis results show that the added mass coefficient for the first torsional mode is in the range of 1.59-1.86,and is around 44%of that for the first bending mode.The trends of the boundary layer thickness and the wake width against the reduced velocity are found to be opposite to that of the hydrodynamic damping ratio.The theoretical equation for predicting the hydrodynamic damping ratio is modified,which is shown to be more reliable due to its consideration of the velocity independent hydrodynamic damping phase.

关键词： Torsional mode hydrodynamic damping added mass hydrofoil Donaldson trailing edge

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聚吡咯基本征可拉伸导电纤维构建及电热理疗应用

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高分子学报 2024年第3期55卷 309-319页

作者：李沂蒙李雯昕刘晓莉唐丽琴王莎莎王富军王璐毛吉富东华大学纺织学院纺织面料技术教育部重点实验室、纺织行业生物医用纺织材料与技术重点实验室、上海市现代纺织前沿科学研究基地上海201620

为解决现有可拉伸电极存在的制备工艺复杂和本征可拉伸性能差的问题,采用简单的原位聚合方法,通过优化掺杂剂,开发了一种具有本征可拉伸性的聚吡咯基导电纤维.在导电纤维的制备过程中,磺基水杨酸钠被用作掺杂剂和增塑剂,使得导电纤维展... 详细信息

为解决现有可拉伸电极存在的制备工艺复杂和本征可拉伸性能差的问题,采用简单的原位聚合方法,通过优化掺杂剂,开发了一种具有本征可拉伸性的聚吡咯基导电纤维.在导电纤维的制备过程中,磺基水杨酸钠被用作掺杂剂和增塑剂,使得导电纤维展现出出色的初始电导率(6.34 S/cm),并且在100%拉伸应变下仍保持5.37 S/cm的良好导电性能.此外,基于弹性导电纤维的加热器具有优秀的焦耳热性能.当施加5V电压时,其表面温度可达到60℃,为热疗提供了可靠的加热效果.进一步将导电纤维集成到电热手套中,实验发现在手指关节运动过程中,手套表面温度仅下降了4.89%,可实现对运动关节的稳定热疗.这为雷诺综合征和关节损伤疼痛等疾病的物理治疗提供了便捷有效的实施方案.

关键词：聚吡咯导电纤维本征可拉伸焦耳热热疗

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