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Evaluation of Subgrid-scale Models in Large-eddy Simulations of Turbulent Flow in a Centrifugal Pump Impeller

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Chinese Journal of Mechanical Engineering 2012年第5期25卷 911-918页

作者： YANG Zhengjun WANG Fujun zhou peijian College of Water Resources&Civil Engineering China Agricultural UniversityBeijing 100083China

The current research of large eddy simulation （LES） of turbulent flow in pumps mainly concentrates in applying conventional subgrid-scale （SGS） model to simulate turbulent flow, which aims at obtaining the flow field in pump. The selection of SGS model is usually not considered seriously, so the accuracy and efficiency of the simulation cannot be ensured. Three SGS models including Smagorinsky-Lilly model, dynamic Smagorinsky model and dynamic mixed model are comparably studied by using the commercial CFD code Fluent combined with its user define function. The simulations are performed for the turbulent flow in a centrifugal pump impeller. The simulation results indicate that the mean flows predicted by the three SGS models agree well with the experimental data obtained from the test that detailed measurements of the flow inside the rotating passages of a six-bladed shrouded centrifugal pump impeller performed using particle image velocimetry （PIV） and laser Doppler velocimetry （LDV）. The comparable results show that dynamic mixed model gives the most accurate results for mean flow in the centrifugal pump impeller. The SGS stress of dynamic mixed model is decompose into the scale similar part and the eddy viscous part. The scale similar part of SGS stress plays a significant role in high curvature regions, such as the leading edge and training edge of pump blade. It is also found that the dynamic mixed model is more adaptive to compute turbulence in the pump impeller. The research results presented is useful to improve the computational accuracy and efficiency of LES for centrifugal pumps, and provide important reference for carrying out simulation in similar fluid machineries.

关键词： large-eddy simulation subgrid-scale model dynamic mixed model centrifugal pump

Effects of Particle Concentration on the Dynamics of a Single-Channel Sewage Pump under Low-Flow-Rate Conditions

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Fluid Dynamics & Materials Processing 2021年第5期17卷 871-886页

作者： peijian zhou Chaoshou Yan Lingfeng Shu Hao Wang Jiegang Mou Research Center on Levee Safety Disaster Prevention Zhengzhou450003China College of Metrology and Measurement Engineering China Jiliang UniversityHangzhouChina College of Mechanical Engineering Zhejiang University of TechnologyHangzhouChina Power China Huadong Engineering Corporation Limited HangzhouChina

Single-channel sewage pumps are generally used to transport solid-liquid two-phase media consisting of a fluid and solid particles due to the good non-clogging property of such ***,the non-axisymmetric structure of the impeller of this type of pumps generally induces flow asymmetry,oscillatory outflow during operations,and hydraulic *** severe cases,these effects can jeopardize the safety and stability of the overall *** the present study,such a problem is investigated in the framework of a Mixture multiphase flow method coupled with a RNG turbulence model used to determine the structure of the flow field and the related motion of transported *** is shown that under different inlet particle concentrations,the flow field in the pump exhibits periodic variations of the *** volume fraction of solid particles at the trailing edge of the suction surface of the blade is the largest,and solid particles tend to be concentrated at the outer edge of the pump *** a rise in import particle content,the pressure and volume fraction of particles in the sewage pump also increase;for a fixed inlet particle concentration,the pressure pulsation amplitude increases with an increase in the flow *** addition,under small flow conditions,as the inlet particle concentration increases,the flow field leaving the sewage pump diaphragm near the outlet of the volute becomes more turbulent,and even a secondary back-flow vortex appears.

关键词： Single-channel sewage pump numerical simulation solid-liquid two-phase flow particle distribution secondary flow

LES Analysis of the Unsteady Flow Characteristics of a Centrifugal Pump Impeller

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Fluid Dynamics & Materials Processing 2022年第5期18卷 1349-1361页

作者： Ting Zhang Denghao Wu Shijun Qiu peijian zhou Yun Ren Jiegang Mou School of Metrology and Measurement Engineering China Jiliang UniversityHangzhouChina Leo Group Pump Co. Ltd.TaizhouChina Zhijiang College Zhejiang University of TechnologyHangzhouChina

Stall phenomena increase the complexity of the internal flow in centrifugal pump *** order to tackle this problem,in the present work,a large eddy simulation(LES)approach is applied to determine the characteristics of these unstable ***,a vorticity identification method is used to characterize quantitatively the vortex position inside the impeller and its influencing *** comparing the outcomes of the numerical simulations and experimental results provided by a Particle Image Velocimetry(PIV)technique,it is shown that an apparent“alternating stall”phenomenon exists inside the impeller when relatively small flow rate conditions are *** stall is generated near the suction side of the blade inlet,grows towards the high-pressure side of the blade in the circumferential direction,and gradually *** the flow rate decreases,the number of stalls remains unchanged,while the related influencing area and strength gradually increase and the circumferential velocity increases.

关键词： Centrifugal pump impeller large eddy simulation unsteady flow stalls vorticity

Chatter suppression techniques in milling processes:A state of the art review

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Chinese Journal of Aeronautics 2024年第7期37卷 1-23页

作者： Zhenmin LI Qinghua SONG peijian JIN Zhanqiang LIU Bing WANG Haifeng MA Key Laboratory of High Efficiency and Clean Mechanical Manufacture Ministry of EducationSchool of Mechanical EngineeringShandong UniversityJinan 250061China National Demonstration Center for Experimental Mechanical Engineering Education Shandong UniversityJinan 250061China

Chatter in the machining system can result in a decrease in tool life,poor surface finish,conservative cutting parameters,*** many review papers promoting the understanding and research of this area,chatter suppression techniques are generally discussed within limited pages in the framework of comprehensive chatter-related *** recent years,the developments of smart materials,advanced sensing techniques,and more effective control strategies have led to some new progress in chatter ***,the widely used thin-walled parts present more and more severe machining challenges in their milling *** the above deficiencies,this paper summarizes the current state of the art in milling chatter *** classifications of chatter suppression techniques are proposed according to the working principle and control *** on the new classified framework,the mechanism and comparisons of different chatter suppression strategies are ***,the current challenges and potential tendencies of milling chatter suppression techniques are ***,integration,compactness,adaptability to workpiece geometry,and the collaboration of multiple control methods are predicted to be important trends in the future.

关键词： Active control Chatter suppression Damping Milling Regenerative effect

New indices to balanceα-diversity against tree size inequality

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Journal of Forestry Research 2024年第1期35卷 229-237页

作者： Li Zhang Brady K.Quinn Cang Hui Meng Lian Johan Gielis Jie Gao peijian Shi College of Ecology and Environment Bamboo Research InstituteNanjing Forestry University159 Longpan RoadNanjing 210037People’s Republic of China Fisheries and Oceans Canada Andrews Biological Station125 Marine Science DriveSt.AndrewsNB E5B 0E4Canada Department of Mathematical Sciences Centre for Invasion BiologyStellenbosch UniversityMatieland 7602South Africa Mathematical and Physical Biosciences African Institute for Mathematical SciencesCape Town 7945South Africa Department of Biosciences Engineering University of AntwerpB-2020 AntwerpBelgium College of Life Science Xinjiang Normal University102 Xinyi RoadUrumqi 830054People’s Republic of China

The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large variations in tree size among species and individu-als of the same species,which result in differences in eco-logical processes and ecosystem ***,tree size inequality(TSI)has been largely neglected in studies using the available diversity *** TSI in the diameter at breast height(DBH)data for each of 99920 m×20 m forest census quadrats was quantified using the Gini index(GI),a measure of the inequality of size *** generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per *** also examined the relationships ofα-diversity indices with the GI using correlation *** generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions,with most root-mean-square errors(990 out of 999 quadrats)being<*** were significant positive correlations between each of threeα-diversity indices(i.e.,R,D,and H’)and the ***,the total abundance of trees in each quadrat did not significantly influence the *** means that the TSI increased with increasing spe-cies ***,two new indices are proposed that can balanceα-diversity against the extent of TSI in the com-munity:(1−GI)×D,and(1−GI)×H’.These new indices were significantly correlated with the original D and H΄,and did not increase the extent of variation within each group of *** study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities,especially in the face of cumulative species loss under global climate change.

关键词： Diameter at breast height(DBH) Gini index Shannon-Wiener index Simpson’s index Quadrat Tree size

Energy Absorption by 3D-Printed Mesh Structures with a Negative Poisson’s Ratio

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 205-212页

作者： Wenyu Li Weiming Yang Mingze Li Xiang Zhang Ping Zhang Yucheng Zhao peijian Chen Haishun Liu School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou221116China School of Materials Sciences and Physics China University of Mining and TechnologyXuzhou221116China

A negative Poisson's ratio(NPR)structure represents optimal impact-resistance with applications in various fields,including the crash box in vehicles,which absorbs impact kinetic *** crash box is designed to deform in response to impact,increasing local structural density,which enhances impact resistance *** studies have only focused on the NPR effect in the plane dimension at low-speed *** studies have considered high-speed impact loads on three-dimensional NPR *** have developed two types of AlSi10Mg alloy energy-absorbing structures with NPR using three-dimensional printing technology,and have compared our systems with a conventional hexagonal mesh *** testing involved split-Hopkinson pressure bar measurements,which showed good agreement with dynamic numerical *** subjected to an impact load,the NPR structure exhibited better impact resistance and energy absorption compared with the positive Poisson's ratio *** proposed dual-layer hexagonal structure ensures an NPR effect while exhibiting higher strength and improved stability relative to the conventional concave hexagon structure.

关键词： Negative Poisson’s ratio Energy absorption 3D printing Split-Hopkinson pressure bar Numerical simulation

Quercetin regulates depression-like behavior in CUMS rat models via TLR4/NF-κB signaling

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BIOCELL 2024年第5期48卷 731-744页

作者： YUANYUAN LI BITAO ZHANG ZILONG CUI peijian FAN SHAOXIAN WANG College of Basic Medicine Hebei University of Chinese MedicineShijiazhuang050200China Hebei Key Laboratory of Integrated Chinese and Western Medicine for Lung Disease Research Shijiazhuang050091China

Background:Depression is becoming increasingly prevalent around the world,imposing a substantial burden on individuals,families,as well as *** is known to be highly effective in treating ***,additional research is needed to dissect the mechanisms of its anti-depressive ***:For this study,Sprague-Dawley(SD)rats were randomized into the control,model,quercetin,or fluoxetine *** latter three groups were exposed to chronic unpredictable mild stress(CUMS)for 42 *** first two groups received saline solution daily via oral ***,the quercetin group was orally administered a quercetin suspension(52.08 mg/kg)every day,while the fluoxetine group was orally administered a fluoxetine solution(2.08 mg/kg).Here,fluoxetine served as the positive control drug to compare the therapeutic effects of *** experimental period was 6 *** behaviors in rats were assessed through various physiological and behavioral ***,pathological changes in hippocampal tissues were examined using Nissl *** cytokines were detected using an enzymelinked immunosorbent assay(ELISA),and immunohistochemistry was employed to quantify the levels and integral optical density(IOD)values of ionized calcium binding adaptor molecule-1(Iba-1)expression in the ***-time fluorescence quantitative PCR(RT-qPCR)was utilized to evaluate the mRNA levels of inflammatory indicators as well as toll-like receptor 4(TLR4),and nuclear factor-κappa B P65(NF-κB P65)in *** blot(WB)technique was employed to observe the protein levels of TLR4,NF-κB P65,and phospho-NF-κB P65(p-NF-κB P65).Results:After 42 d of exposure to CUMS,rats exhibited a slow increase in body weight,a reduction in food intake,an abnormal preference for sugar water,and aberrant open-field *** analysis revealed the disintegration,rupture,interruption,and disorganization of hippocampal neuronal cells after CUMS exposure

关键词： Quercetin Chronic unpredictable mild stress Depression Microglia TLR4/NF-κB inflammatory pathway

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旋转失速条件下离心泵叶轮压力脉动特性研究

农业机械学报 2015年第10期46卷 56-61页

作者：周佩剑王福军姚志峰中国农业大学水利与土木工程学院北京100083

离心泵发生旋转失速时,失速团周期性地生成和脱落往往会诱发低频压力脉动,严重影响水泵的安全稳定运行。为研究离心泵旋转失速对压力脉动的影响,采用动态混合非线性SGS模型对一离心泵叶轮进行了大涡模拟,得到了叶轮内部流场和叶片上的... 详细信息

离心泵发生旋转失速时,失速团周期性地生成和脱落往往会诱发低频压力脉动,严重影响水泵的安全稳定运行。为研究离心泵旋转失速对压力脉动的影响,采用动态混合非线性SGS模型对一离心泵叶轮进行了大涡模拟,得到了叶轮内部流场和叶片上的压力脉动特性。对不同旋转时刻的内部流动进行分析,可以看到旋转失速团产生于叶片吸力面头部附近,沿圆周方向向叶片压力面运动,并逐渐衰减。对叶片上的压力脉动进行分析,发现当旋转失速发生以后,叶片上的压力脉动幅值远大于非失速工况。失速团对叶轮中的压力脉动有很大影响,叶片上的压力脉动频率以失速频率为主;叶片吸力面头部压力脉动幅值最大,并沿着水流方向,叶片上的压力脉动幅值依次减小。随着流量进一步减小,叶轮进入深失速工况,压力脉动主频幅值有所降低,而失速频率逐渐增大。

关键词：离心泵叶轮旋转失速压力脉动大涡模拟

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叶片数对离心泵叶轮失速特性影响研究

机械工程学报 2016年第10期52卷 207-212页

作者：周佩剑王福军姚志峰中国农业大学水利与土木工程学院北京100083 浙江工业大学机械工程学院杭州310014

为研究叶片数对离心泵叶轮失速特性的影响,以4种不同叶片数的离心泵叶轮为研究对象,采用改进的亚格子模型(Sub-grid scale model,SGS)对叶轮的内部流场进行数值模拟,得到不同叶片数的失速团的运动规律,以及失速频率、失速团个数、转速... 详细信息

为研究叶片数对离心泵叶轮失速特性的影响,以4种不同叶片数的离心泵叶轮为研究对象,采用改进的亚格子模型(Sub-grid scale model,SGS)对叶轮的内部流场进行数值模拟,得到不同叶片数的失速团的运动规律,以及失速频率、失速团个数、转速等特性参数。研究表明,叶片数对叶轮内部失速团的类型有显著影响,当叶片数为偶数时,会发生'交替失速'流动现象;当叶片数为奇数时,会发生'旋转失速'流动现象。另外,叶片数对失速团特征参数也有一定影响。当发生'交替失速'时,叶片数增多,失速团的数量也随之增多,失速频率也随之变化,4叶片叶轮失速团的失速频率约是6叶片的2.4倍;而当发生'旋转失速'时,叶片数增多,失速团的数量也随之增多,转速也随之增大,7叶片叶轮失速团的转速约是5叶片的1.8倍,失速频率是它的3.8倍。

关键词：离心泵叶片数交替失速旋转失速