International faculty in China: case studies of four leading universities in Shanghai

Xian Wu,Futao HUANG 서울대학교 교육연구소 2018 Asia Pacific Education Review Vol.19 No.2

To attract and hire high-level international faculty to leading universities is an important task in building world-class universities in China. However, there is much left to explore and to understand about international faculty in China. Based on a brief review of China’s higher education system and international faculty, findings from A National Survey of International Faculty at Chinese Universities and Colleges (conducted in 2017), and case studies of four leading universities in Shanghai, this study explores the main characteristics and motivations of international faculty in China by discipline, age, gender, and so forth. More specially, it explores the individual, educational, and professional characteristics of international faculty at Chinese colleges and universities, how these characteristics vary among different groups of international faculty, and why they came to Chinese leading universities?

Impeller inlet geometry effect on performance improvement for centrifugal pumps

Xianwu Luo,Yao Zhang,Junqi Peng,Hongyuan Xu,Weiping Yu 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.10

This research treats the effect of impeller inlet geometry on performance improvement for a boiler feed pump, who is a centrifugal pump having specific speed of 183 m⋅m3min-1⋅min-1 and close type impeller with exit diameter of 450 mm. The hydraulic performance and cavitation performance of the pump have been tested experimentally. In order to improve the pump, five impellers have been considered by extending the blade leading edge or applying much larger blade angle at impeller inlet compared with the original impeller. The 3-D turbulent flow inside those pumps has been analyzed basing on RNG k-ε turbulence model and VOF cavitation model. It is noted that the numerical results are fairly good compared with the experiments. Based on the experimental test and numerical simulation, the following conclusions can be drawn: (1) Impeller inlet geometry has important influence on performance improvement in the case of centrifugal pump. Favorite effects on performance improvement have been achieved by both extending the blade leading edge and applying much larger blade angle at impeller inlet; (2) It is suspected that the extended leading edge have favorite effect for improving hydraulic performance, and the much larger blade angle at impeller inlet have favorite effect for improving cavitation performance for the test pump; (3) Uniform flow upstream of impeller inlet is helpful for improving cavitation performance of the pump.

Comparison of cavitation prediction for a centrifugal pump with or without volute casing

Xianwu Luo,Wei Wei,Bin Ji,Zaibing Pan,Wenchao Zhou,Hongyuan Xu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6

Cavitation may not only cause head and efficiency breakdown of hydraulic machines but also generate other unfavorable phenomena such as noise and vibration. Therefore, the accurate prediction of cavitation development is important for various pump applications. In this paper, two numerical models, namely, models A and B, are applied to simulate the turbulent cavitating flows inside a centrifugal pump to investigate the effect of calculation domain on the prediction accuracy of cavitation performance for hydraulic machines. Model A has a calculation domain with volute casing, whereas model B has a single blade-to-blade flow passage without volute casing. Steady simulations of cavitating flow in the pump have been conducted based on the shear stress transport k-ω turbulence model and the homogeneous cavitation model. Both models A and B predicted that the pump performance decreases with decreasing cavitation number. Experimental results show that model B can predict better the critical cavitation number at the best efficiency point compared with model A, which is the full flow passage model. Internal flow investigations indicate that an asymmetrical feature of cavitating flow exists when the calculation domain with volute casing is applied. The asymmetrical cavitation development in different blade-to-blade flow passages for model A results in an over-estimation of the decrease in pump performance because of the interaction between the impeller blade and the tongue of the volute casing. A simple calculation domain without volute casing is preferred for steady cavitation prediction in pumps rather than the full flow passage with volute casing because the former has better convergence, less resource requirements, and lower time consumption.

Unsteady cavitation characteristics and alleviation of pressure fluctuations around marine propellers with different skew angles

Bin Ji,Xianwu Luo,Yulin Wu 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4

Cavitating flow around two marine propellers with different skew angles, a conventional propeller (CP) and a highly skewed propeller(HSP), operating in the non-uniform wake was simulated using a mass transfer cavitation model and the k-omega SST turbulence model. The numerical model reasonably predicted experimental data for the unsteady cavitation patterns as well as the oscillation amplitudes ofthe dominant pressure components. The results indicate that the effect of skew angle is very important on the cavitation characteristics aswell as the pressure fluctuations and that the amplitudes of pressure fluctuations for the HSP are 50~70% less than that for the CP. Therefore,the skewed propeller will reduce noise and vibration compared to the conventional propeller. Furthermore, the numerical modelverified the relation between the hull pressures and changing cavitation patterns as the blades sweep through the high wake region. Theresults demonstrate that volumetric acceleration of entire cavity around a propeller blade is the main reason for the pressure fluctuations,which agrees with previous experiments.

Numerical simulation of the transient cavitating turbulent flows around the Clark-Y hydrofoil using modified partially averaged Navier-Stokes method

Renfang Huang,Xianwu Luo,Bin Ji 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6

This paper presents the implementation and assessment of a modified Partially averaged Navier-Stokes (PANS) turbulence modelwhich can successfully predict the transient cavitating turbulent flows. The proposed model treats the standard k-e model as the parentmodel, and its main distinctive features are to (1) formulate the unresolved-to-total kinetic energy ratio (fk) based on the local grid size aswell as turbulence length scale, and (2) vary the fk-field both in space and time. Numerical simulation used the modified PANS model forthe sheet/cloud cavitating flows around a three-dimensional Clark-Y hydrofoil. The available experimental data and calculations of thestandard k-e model, the fk = 0.8 PANS model, the fk = 0.5 PANS model are also provided for comparisons. The results show that themodified PANS model accurately captures the transient cavitation features as observed in experiments, namely, the attached sheet cavitygrows in the flow direction until to a maximum length and then it breaks into a highly turbulent cloud cavity with three-dimensionalstructures in nature. Time-averaged drag/lift coefficients together with the streamwise velocity profiles predicted by the proposed modelare in good agreement with the experimental data, and improvements are shown when compared with results of the standard k-e model,the fk = 0.8 PANS model and the fk = 0.5 PANS model. Overall, the modified PANS model shows its encouraging capability of predictingthe transient cavitating turbulent flows.

Numerical investigation of three-dimensional cavitation evolution and excited pressure fluctuations around a twisted hydrofoil

Bin Ji,Xianwu Luo,Yulin Wu,Kazuyoshi Miyagawa 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

Unsteady cavitating turbulent flow around a twisted hydrofoil was analyzed to illustrate the physical mechanism of the cavitygeneratedpressure fluctuations. The numerical simulations of cavitating flow were based on the Partially-Averaged Navier-Stokes(PANS) method and a mass transfer cavitation model. The validity of PANS model has been evaluated and confirmed in cavitation simulationsby present authors using three different cases, 2D hydrofoil (Ji et al. 2012 [37]), 3D hydrofoil (Ji et al. 2013 [31]) and marine propeller(Ji et al. 2012 [38]), which shows that the PANS model with fk = 0.2 and fe = 1 can obtain more accurate estimates of unsteadycavitating flows with large-scale fluctuations at a reasonable cost. In present paper we intended to shed light on the physical process responsiblefor the pressure fluctuations excited by cavitation. The cavity volume was analyzed to illustrate the relationship between thecavitation evolution and the pressure fluctuations. The results show that the cavity volumetric acceleration curve tracks remarkably wellwith the main features of the time-dependent pressure fluctuations except for the high frequency component. Thus, the cavity volumetricacceleration is the main source of the excited pressure fluctuations by cavitation. It is noted that the cavitation induced pressure fluctuationsare transmitted along the suction surface of the hydrofoil and are synchronized with those on the pressure surface at the midplane ofthe twisted hydrofoil. Further, the pressure fluctuations on the pressure surface decrease towards the center from both the leading andtrailing edges of the hydrofoil, with a minimum at 60% chord length from the leading edge.

Cavitation in a Shaft-less Double Suction Centrifugal Miniature Pump

Zhuang, Baotang,Luo, Xianwu,Zhu, Lei,Wang, Xin,Xu, Hongyuan Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1

Based on the consideration that the cavitation would affect the operation stability of miniature pumps, the 3-D turbulent cavitating flow in a test pump was simulated by using a mixed cavitation model and k-${\omega}$ SST turbulence model. In order to investigate the influence of inlet geometry parameters on the cavitation performance of the miniature pump, two more impellers are designed for comparison. Based on the results, the following conclusions are drawn: 1) Cavitation performance of the double suction shaft-less miniature pump having different impeller is equivalent to the centrifugal pump having ordinary size, though the flow passage at impeller inlet is small; 2) The miniature pump having radial impeller can produce much higher pump head, but lower cavitation performance than that having the impeller based on the conventional design method; 3) It is believed that by applying the double suction design, the miniature pump achieved relatively uniform flow pattern upstream the impeller inlet, which is favorable for improving cavitation performance.

Numerical investigation of cavitation-vortex interaction in a mixed-flow waterjet pump

Renfang Huang,Bin Ji,Xianwu Luo,Zhihong Zhai,Jiajian Zhou 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9

Turbulent cavitating flows in a mixed-flow waterjet pump were numerically investigated using the k-w SST turbulence model and themass transfer cavitation model based on the Rayleigh-Plesset equation to provide a comprehensive understanding of the cavitation-vortexinteraction mechanism. The predicted hydraulic performance, as well as the cavitation performance, exhibits a reasonable agreement withthe experimental results. The vorticity distributions under three operation conditions were illustrated together. Based on the illustration,cavitation development enhances vorticity production and flow unsteadiness in a mixed-flow waterjet pump. Vortices are basically locatedat the cavity interface, particularly at the downstream interface, during cavitation. Further analyses using the relative vorticity transportequation in cavitating turbulent flows indicate that vortex dilation and baroclinic torque exhibit a steep jump as cavitation occurs. Inaddition, vortex stretching contributes mainly to large-scale vortex generation.

Experiment Investigation on Fluid Transportation Performance of Propellant Acquisition Vanes in Microgravity Environment

Baotang Zhuang,Yong Li,Xianwu Luo,Halin Pan,Jingjing Ji 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.1

The propellant acquisition vane (PAV) is a key part of a vane type surface tension propellant management device (PMD), which can manage the propellant effectively. In the present paper, the fluid transportation behaviors for five PAVs with different sections were investigated by using microgravity drop tower test. Further, numerical simulation for the propellant flow in a PMD under microgravity condition was also carried out based on VOF model, and showed the similar flow pattern for PAVs to the experiment. It is noted that the section geometry of PAVs is one of the main factors affecting the fluid transportation behavior of PMD. PAVs with bottom length ratio of 5/6 and 1/2 have larger propellant transportation velocity. Based on the experiments, there were two stages during the process of propellant transportation under microgravity environment: liquid relocation and steady transportation stage. It is also recognized that there is a linear correlation between liquid transportation velocity and relative time's square root. Those results can not only provide a guideline for optimization of new vane type PMDs, but also are helpful for fluid control applications in space environment.

Investigation on the Flow Field Upstream of a Centrifugal Pump Impeller

Zhang, Yao,Luo, Xianwu,Yi, Yunchi,Zhuang, Baotang,Xu, Hongyuan Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1

The flow upstream of a centrifugal pump impeller has been investigated by both experimental test and numerical simulation. For experimental study, the flow field at four sections in the pump suction is measured by using PIV method. For calculation, the three dimensional turbulent flow for the full flow passage of the pump is simulated based on RANS equations combined with RNG k-$\varepsilon$ turbulence model. From those results, it is noted that at both design lo ad and quarter load condition, the pre-swirl flow whose direction is the same as the impeller rotation exists at all four sections in suction pipe of the pump, and at each section, the pre-swirl velocity becomes obviously larger at higher rotational speed. It is also indicated that at quarter load condition, the low pressure region at suction surface of the vane is large because of the unfavorable flow upstream of the pump impeller.