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Lower bound for transient growth of inclined buoyancy layer

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Applied Mathematics and Mechanics(English Edition) 2017年第6期38卷 779-796页

作者： Xiangming XIONG jianjun tao Center for Applied Physics and Technology (CAPT)-MOE Key Laboratory of High Energy Density Physics Simulation (HEDPS) State Key Laboratory for Turbulence and Complex System (SKLTCS)Department of Mechanics and Engineering ScienceCollege ofEngineeringPeking University

The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.

关键词： natural convection boundary layer energy method transient growth

Viscous Rayleigh-Taylor instability with and without diffusion effect

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Applied Mathematics and Mechanics(English Edition) 2017年第2期38卷 263-270页

作者： Chenyue XIE jianjun tao Ji LI Center for Applied Physics and Technology (CAPT)-MOE Key Laboratory of High Energy Density Physics Simulation (HEDPS) State Key Laboratory for Turbulence and Complex System (SKLTCS) Department of Mechanics and Engineering ScienceCollege of Engineering Peking University Department of Engineering University of Cambridge

The approximate but analytical solution of the viscous Rayleigh-Taylor insta- bility （RTI） has been widely used recently in theoretical and numerical investigations due to its clarity. In this paper, a modified analytical solution of the growth rate for the viscous RTI of incompressible fluids is obtained based on an approximate method. Its accuracy is verified numerically to be significantly improved in comparison with the previous one in the whole wave number range for different viscosity ratios and Atwood numbers. Fur- thermore, this solution is expanded for viscous RTI including the concentration-diffusion effect.

关键词： viscous Rayleigh-Taylor instability (RTI) dispersion relation diffusioneffect

Heat transfer characteristics in a narrow confined channel with discrete impingement cooling

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Chinese Journal of Aeronautics 2022年第4期35卷 220-229页

作者： Yang LI tao LIU jianjun tao Weihua YANG Likun DONG Hunan Key Laboratory of Turbomachinery on Small and Medium Aero-Engine AECC Hunan Aviation Powerplant Research InstituteZhuzhou 412002China College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Heat transfer characteristics in a narrow confined channel with discrete impingement cooling were investigated using thermal infrared camera. Detailed heat transfer distributions and comparisons on three surfaces with three impact diameters were experimentally studied in the range of Reynolds number of 3000 to 30000. The experimental results indicated that the strong impingement jet leaded to a high strength heat transfer zone in the ΔX=±2.5D;range of the impact center,which was 1.3–2.5 times of the average heat transfer value of the impingement wall. With the same coolant mass flow rate, small diameter case had lower heat transfer coefficient on both inner wall and outside wall, while the impingement wall was insensitive to the impact diameter. The surface averaged Nusselt number of inner wall was only 43%–57% of impingement wall, while the outside wall can reach up to 80%–90%. The larger the diameter, the higher heat transfer enhancement and the smaller the channel flow resistance was observed in term of Reynolds number. The surface averaged Nusselt numbers were developed as the function of Reynolds number and the impingement height-to-diameter for further engineering applications.

关键词： Aero-engine Heat transfer characteristics Impingement cooling Narrow confined channel Turbine blade

Local Reynolds number and thresholds of transition in shear flows

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Science China(Physics,Mechanics & Astronomy) 2013年第2期56卷 263-269页

作者： tao jianjun CHEN ShiYi SU WeiDong SKLTCS and CAPT Department of Mechanics and Aerospace EngineeringCollege of EngineeringPeking University

Recent experimental and numerical investigations reveal that the onset of turbulence in plane-Poiseuille flow and planeCouette flow has some similar stages separated with different threshold Reynolds *** on these observations and the energy equation of a disturbed fluid element,a local Reynolds number Re L is derived to represent the maximum ratio of the energy supplement to the energy dissipation in a cross *** is shown that along the sequence of transition stages,which include transient localized turbulence,"equilibrium" localized turbulence,spatially intermittent but temporally persistent turbulence and uniform turbulence,the corresponding thresholds of Re L for plane-Couette flow,Hagen-Poiseuille flow and plane-Poiseuille flow are consistent,indicating that the critical(threshold) states during the laminar-turbulent transition are determined by the local properties of the base flow and are independent of global features,such as flow geometries(pipe or channel) and types of driving forces(shear driving or pressure driving).

关键词： shear flow transition localized turbulence

Threshold and decay properties of transient isolated turbulent band in plane Couette flow

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Applied Mathematics and Mechanics(English Edition) 2019年第10期40卷 1449-1456页

作者： Jianzhou LU jianjun tao Weitao ZHOU Xiangming XIONG CAPT-HEDPS SKLTCS Collaborative Innovation Center of IFSA Department of Mechanics and Engineering Science College of Engineering Peking University Beijing 100871 China The Program in Applied and Computational Mathematics Princeton University Princeton NJ 08544 U. S.A.

By direct numerical simulations of the plane Couette flow (PCF) in a large computational domain, it is shown that an isolated turbulent band decays monotonically at low Reynolds numbers but experiences transient growth before the eventual relaminarization at moderate Reynolds numbers. The lower bound Reynolds number of the transient-growth regime is determined as 286. The width, length, and tilt angle of the iso- lated band structure are defined based on the disturbance kinetic energy in the mid-plane, and the geometric characteristics of the band can be described with a tilted rectangle. It is illustrated that before its eventual fragmentation, the isolated turbulent band decays in a style of longitudinal contraction, where the center, width, and tilt angle of the band keep almost constant but the band length contracts with a statistically constant velocity.

关键词： plane Couette flow (PCF) subcritical transition turbulent band

Editorial:Recent advances in hydrodynamic instability and transition to turbulence

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Theoretical & Applied Mechanics Letters 2015年第3期5卷 101-102,I0004页

作者： Luca Brandt jianjun tao Linné FLOW Centre KTH Mechanics CAPT HEDPSand IFSA Collaborative Innovation Center of MoEDepartment of Mechanics and Engineering ScienceCollege of EngineeringPeking University

Hydrodynamic instability and the mechanisms for turbulence onset and self-sustaining are two research questions that have puzzled the scientists for over a century, yet renewed interest and significant progress occurred in the last decade or so. We know only few exact analytical solutions of the Navier-Stokes equations, the equations governing the flow of simple fluids like water and air, and most of these are never observed in applications or laboratory experiments since these configurations are prone to instabilities that quickly bring the flow to the turbulent regime.

关键词： turbulence instability hydrodynamic exact renewed advances Stokes Navier questions turbulent

The Absolute and Convective Secondary Instabilities in the Conduction Regime

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Communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 34-38页

作者： jianjun tao and Dachun YAN (Dept. of Mechanics & Engineering Sciences,Peking University, Beijing 100871, China) Dept. of Mechanics & Engineering Sciences Peking University Beijing 100871 China

Convective and absolute instabilities in the conduction regime of a vertical heated slot are investigated. It is found that in a large range of Prandtl number (0 12, a secondary instability appears with stationary mo... 详细信息

关键词： absolute instability convective instability conduction regime

Spatial-temporal Pattern and Population Driving Force of Land Use Change in Liupan Mountains Region, Southern Ningxia, China

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Chinese Geographical Science 2008年第4期18卷 323-330页

作者： QUAN Bin M J M ROMKENS tao jianjun LI Bicheng LI Chaokui YU Guanghui CHEN Qichun Institute of Geospatial Information Science Hunan University of Science and Technology Xiangtan 411201 China USDA/ARS National Sedimentation Laboratory P O. Box 1157 Oxford MS 38655 USA Researeh Center of Soil and Water Conservation and Ecological Environment Chinese Academy of Sciences and Ministry of Education Northwest Sci-tech University of Agriculture and Forestry Yangling 712100 China

The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains region has suffered tremendous ecological damages over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. In this paper, datasets of land use between 1990 and 2000 were obtained from Landsat TM imagery, and then spatial models were used to characterize landscape conditions. Also, the relationship between the population density and land use/cover change (LUCC) was analyzed. Results indicate that cropland, forestland, and urban areas have increased by 44,186ha, 9001ha and 1550ha, respectively while the grassland area has appreciably decreased by 54,025ha in the study period. The decrease in grassland was most notable. Of the grassland lost, 49.4% was converted into cropland. The largest annual land conversion rate in the study area was less than 2%. These changes are attributed to industrial and agricultural development and population growth. To improve the eco-economic conditions in the study region, population control, urbanization and development of an ecological friendly agriculture were suggested.

关键词： land use/cover change (LUCC) GIS remote sensing Liupan Mountains region Loess Plateau

Key role of interferon regulatory factor 1(IRF-1)in regulating liver disease:progress and outlook

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2024年第6期25卷 451-470页

作者： tao CHEN Shipeng LI Dewen DENG Weiye ZHANG jianjun ZHANG Zhongyang SHEN First Central Clinical School Tianjin Medical UniversityTianjin 300192China Department of Organ Transplant Tianjin First Central HospitalTianjin 300192China Research Institute of Transplant Medicine Nankai UniversityTianjin 300192China Department of Hepatobiliary Surgery Henan Provincial People’s HospitalZhengzhou 450000China Key Laboratory of Organ Transplant Tianjin First Central HospitalTianjin 300192China

Interferon regulatory factor 1(IRF-1)is a member of the IRF *** is the first transcription factor to be identified that could bind to the interferon-stimulated response element(ISRE)on the target gene and displays crucial roles in the interferoninduced signals and ***-1,as an important medium,has all of the advantages of full cell cycle regulation,cell death signaling transduction,and reinforcing immune surveillance,which are well *** studies indicate that IRF-1 is of vital importance to the occurrence and evolution of multifarious liver diseases,including but not limited to inhibiting the replication of the hepatitis virus(A/B/C/E),alleviating the progression of liver fibrosis,and aggravating hepatic ischemiareperfusion injury(HIRI).The tumor suppression of IRF-1 is related to the clinical characteristics of liver cancer patients,which makes it a potential indicator for predicting the prognosis and recurrence of liver cancer;additionally,the latest studies have revealed other effects of IRF-1 such as protection against alcoholic/non-alcoholic fatty liver disease(AFLD/NAFLD),cholangiocarcinoma suppression,and uncommon traits in other liver diseases that had previously received little ***,several compounds and drugs have featured a protective function in specific liver disease models in which there is significant involvement of the IRF-1 *** this paper,we hope to propose a prospective research basis upon which to help decipher translational medicine applications of IRF-1 in liver disease treatment.

关键词： Interferon regulatory factor(IRF-1) Hepatitis virus Liver fibrosis Hepatic ischemia-reperfusion injury(HIRI) Liver cancer