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Influence of wall effect on Comprehensive Controllability for Ducted Fan Aircraft

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Journal of Beijing Institute of Technology 2020年第4期29卷 581-591页

作者： Tianfu Ai Changle Xiang Bin Xu Wei Fan Yibo Zhang Vehicle Research Center School of Mechanical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China

A novel coaxial ducted fan structure aircraft is proposed to enable the aircraft near vertical walls at high altitudes.The state space equation of the system can be obtained by correlation deduction and identification of the whole prototype model.Based on the duct test bench experiment and computational fluid dynamics(CFD)simulation analysis,the expressions between the different distances dWE from the rotor center of the prototype to the wall and the thrust,reaction torque,and tilting moment of the system under hovering conditions are obtained.The influence of the wall effect of the prototype is incorporated into the system model to analyze the relationship between distance dWE and the comprehensive controllability of the system.The results show that the system comprehensive controllability vector of other channels changes little with the decrease of the distance dWE,and only the controllability vector of the rolling channel increases significantly.At the same time,the tilting moment also increases significantly,which strengthens the tendency of the prototype to tilt towards the wall.

关键词： coaxial ducted fan aircraft hovering condition wall effect tilting moment comprehensive controllability analysis

Application of smog chambers in atmospheric process studies

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National Science Review 2022年第2期9卷 126-141页

作者： Biwu Chu Tianzeng Chen Yongchun Liu Qingxin Ma Yujing Mu Yonghong Wang Jinzhu Ma Peng Zhang Jun Liu Chunshan Liu Huaqiao Gui Renzhi Hu Bo Hu Xinming Wang Yuesi Wang Jianguo Liu Pinhua Xie Jianmin Chen Qian Liu Jingkun Jiang Junhua Li Kebin He Wenqing Liu Guibin Jiang Jiming Hao Hong He State Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Center for Excellence in Regional Atmospheric Environment Institute of Urban Environment Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences Aerosol and Haze Laboratory Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Beijing Convenient Environmental Tech Co.Ltd Key Laboratory of Environmental Optics and Technology Anhui Institutes of Optics and Fine Mechanics Chinese Academy of Sciences State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization Guangzhou Institute of Geochemistry Chinese Academy of Sciences Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention Department of Environmental Science and Engineering Fudan University

Smog chamber experimental systems,which have been widely used in laboratory simulation for studying atmospheric processes,are comprehensively reviewed in this paper.The components,development history,main research topics and main achievements of smog chambers are introduced.Typical smog chambers in the world,including their volumes,wall materials,light sources and features,are summarized and compared.Key factors of smog chambers and their influences on the simulation of the atmospheric environment are discussed,including wall loss,wall emission and background pollutants.The features of next-generation smog chambers and their application prospect in future studies of the atmospheric environment are also outlined in this paper.

关键词： smog chamber simulation wall effect secondary aerosol ozone

Settling behavior of spherical particles in vertical annulus:Experimental study and model development

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Particuology 2022年第9期20卷 114-123页

作者： Zhaopeng Zhu Mengmeng Zhou Xianzhi Song Shuo Zhu Gensheng Li Zhengming Xu Xuezhe Yao Buwen Yu State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing 102249China ARC Research Hub for Computational Particle Technology Department of Chemical&Biological EngineeringMonash UniversityClaytonVictoria 3800Australia China University of Geosciences Beijing 100089China

Coiled tubing(CT)drilling technology offers significant advantages in terms of cost and efficiency for exploitations of unconventional oil and gas resources.However,the development of CT drilling technol-ogy is restricted by cuttings accumulation in the wellbore due to non-rotation of the drill string and limited circulating capacity.Cuttings cleaning becomes more difficult with the wall resistance of pipe-wellbore annulus on the cutting transport.Accurate description of particle transport process in the pipe-wellbore annulus is,therefore,important for improving the wellbore cleanliness.In this study,high-speed cam-era is used to record and analyze the settling process of particles in the transparent annulus filled with power-law fluids.A total of 540 tests were carried out,involving dimensionless diameters of 0.10-0.95 and particle Reynolds Numbers of 0.01-12.97,revealing the effect of the dimensionless diameter and particle Reynolds number on the annulus wall effect,and the wall factor model with an average relative error of2.75%was established.In addition,a dimensionless parameter,Archimedes number,independent of the settling velocity,was introduced to establish an explicit model of the settling velocity of spherical particles in the vertical annulus,with the average relative error of 7.89%.Finally,a calculation example was provided to show how to use the explicit model of settling velocity in annulus.The results of this study are expected to provide guidance for field engineers to improve the wellbore cleanliness of coiled tubing drilling.

关键词： Coiled tubing drilling Micro annulus Spherical particle wall effect Settling velocity

Settling behavior of spherical particles in eccentric annulus filled with viscous inelastic fluid

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Petroleum Science 2022年第4期19卷 1653-1663页

作者： Zhao-Peng Zhu Xian-Zhi Song Ergun Kuru Hong-Bo Chen Bu-Wen Yu Zi-Chao Lin Yan-Xin Sun China University of Petroleum-Beijing Beijing102249China University of Alberta Edmonton10230Canada State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum-BeijingBeijing102249China

Hole cleaning is a complex process as there are many variables affecting cuttings removal(e.***.drilling fluid type,density,flow rate and rheological properties,cuttings size,drill pipe rotation speed).With the increasing number of drilling small diameter wells(e.***.coiled tubing drilling applications,ultra-deep wells drilled for exploitations of unconventional oil and gas resources),the wall resistance of the micro annulus also emerges as one of the most critical factors affecting the cuttings accumulation in wellbore.The eccentricity of drill pipes commonly observed during the drilling process of ultra-deep well and coiled tubing well makes the wall resistance effect on the cuttings transport even more prominent.Understanding the wall resistance effect on the particle settling behavior in eccentric annuli is,therefore,crucial for hydraulic design of efficient cuttings transport operations in these wells.In this study,a total of 196 sets of particle settling experiments were carried out to investigate the particle settling behavior in eccentric annuli filled with power-law fluids.The test matrix included the eccentricity ranges of 0-0.80,the dimensionless diameter ranges of 0.13-0.75 and the particle Reynolds number ranges of 0.09-32.34.A high-speed camera was used to record the particle settling process and determine the influences of the eccentricity,the dimensionless diameter,the fluid rheological properties,and the solid particle characteristics on the wall factor and the particle settling velocity.The functional relationship among the dimensionless diameter,the particle Reynolds number,and the wall factor was determined by using the method of controlling variables.An eccentric annulus wall factor model with average relative error of 5.16%was established.Moreover,by introducing Archimedes number,an explicit model of particle settling velocity in the eccentric annulus with average relative error of 10.17%was established.A sample calculation of particle settling velocity was provided to show the application of th

关键词： Cuttings transport Particle settling velocity Eccentric annulus wall effect

Three-dimensional dynamics of a single bubble rising near a vertical wall:Paths and wakes

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Petroleum Science 2023年第3期20卷 1874-1884页

作者： Hong-jie Yan He-Yang Zhang Hui-Min Zhang Yi-Xiang Liao Liu Liu School of Energy Science and Engineering Central South UniversityChangsha410083PR China Institute of Fluid Dynamics Hemholtz-zentrum Dresden-RossendorfD-01328DresdenGermany

In order to clarify the migration mechanism and wake behavior of a single bubble rising near a vertical wall,three-dimensional direct numerical simulations are implemented based on the open-source soft-ware Basilisk and various types of migration paths like linear,zigzag and spiral are investigated.The volume of fluid(VOF)method is used to capture the bubble interface at a small scale,while the gas-liquid interface and high-velocity-gradient regions in the flow field are encrypted with the adaptive mesh refinement technology.The results show that the vertical wall has an obstructive effect on the diffusion of the vortex boundary layer on the surface of the bubble migrating in a straight line,and the resulting reaction force tends to push the bubbles away from the wall surface.For the zigzag or spiral movement of a bubble in the x-y plane,the perpendicular wall is an unstable factor,but on the contrary,the motion in the z-y plane is stabilized.

关键词： Bubble wall effect Trajectory Wake structure VOF Basilisk

Motion through spherical droplet with non-homogenous porous layer in spherical container

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Applied Mathematics and Mechanics(English Edition) 2020年第7期41卷 1069-1082页

作者： P.K.YADAV A.TIWARI P.SINGH Department of Mathematics Motilal Nehru National Institute of Technology AllahabadPrayagraj 211004India Department of Mathematics Birla Institute of Technology SciencePilani 333031Rajasthan Department of Mathematics National Institute of Technology PatnaPatna 800005India

The problem of the creeping flow through a spherical droplet with a non-homogenous porous layer in a spherical container has been studied analytically.Darcy’s model for the flow inside the porous annular region and the Stokes equation for the flow inside the spherical cavity and container are used to analyze the flow.The drag force is exerted on the porous spherical particles enclosing a cavity,and the hydrodynamic permeability of the spherical droplet with a non-homogeneous porous layer is calculated.Emphasis is placed on the spatially varying permeability of a porous medium,which is not covered in all the previous works related to spherical containers.The variation of hydrodynamic permeability and the wall effect with respect to various flow parameters are presented and discussed graphically.The streamlines are presented to discuss the kinematics of the flow.Some previous results for hydrodynamic permeability and drag forces have been verified as special limiting cases.

关键词： non-homogenous porous medium Stokes equation Darcy’s law perme-ability parameter wall effect

COALESCENCE INDUCED GRADIENT MORPHOLOGY NEAR A wall IN PHASE SEPARATED POLYMER BLENDS DURING QUIESCENT ANNEALING

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Chinese Journal of Polymer Science 2002年第6期20卷 543-550页

作者： Wei Yu Chi-xing Zhou De-lu Zhao Department of Polymer Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 China State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences Beijing 100080, China Department of Polymer Science and Engineering Shanghai Jiao Tong University 上海 200240 Institute of Chemistry Chinese Academy of Sciences State Key Laboratory of Polymer Physics and Chemistry 北京 100080

A fast coalescence mechanism is proposed to account for the wall effect on the formation of gradient morphology in phase separated polymer blends during quiescent annealing. The existence of solid wall with high polarity is believed to change the potential field around the dispersed particles near the wall. This additional potential interaction between the solid wall and the dispersed particles causes faster coalescence of the dispersed particles near the wall than in the bulk. The gradient phase morphology thus formed can be predicted by combining the wall-particle interaction and the touch-coalescence mechanism. The effect of interfacial tension on the gradient morphology is also discussed.

关键词： gradient morphology wall effect coalescence polymer blends interfacial tension

Aerodynamic Performance of a Flapping Foil with Asymmetric Heaving Motion near a wall

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Journal of Bionic Engineering 2018年第4期15卷 636-646页

作者： Xingjian Lin Shuhao Guo Jie Wu Jingwen Nan Department of Aerodynamics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The effect of asymmetric heaving motion on the aerodynamic performance of a two-dimensional flapping foil near a wall is studied numerically. The foil executes the heaving and pitching motion simultaneously. When the heaving motion is symmetric, the mean thrust coefficient monotonically increases with the decrease in mean distance between foil and wall. Meanwhile, the mean lift coefficient first increases and then decreases sharply. In addition, the negative mean lift coefficient appears when the foil is very close to the wall. After the introduction of asymmetric heaving motion, the influence of wall effect on the force behavior becomes complicated. The mean thrust coefficient is enhanced when the duration of upstroke is reduced. Moreover, more and more enhancement can be achieved when the foil approaches the wall gradually. On the other hand, the positive mean lift coefficient can be observed when the duration of downstroke is shortened. By checking the flow patterns around the foil, it is shown that the interaction between the vortex shed from the foil and the wall can greatly modify the pressure distribution along the foil surface. The results obtained here might be utilized to optimize the kinematics of the Micro Aerial Vehicles （MAVs） flying near a solid wall.

关键词： asymmetric heaving motion wall effect thrust enhancement positive mean lift

Settling velocity of equiaxed dendrites in a tube

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Chinese Physics B 2013年第1期22卷 518-523页

作者：周鹏王猛林鑫黄卫东 State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The settling velocity of equiaxed dendrites can cause macrosegregation and influence the structure of the equiaxed zone during the casting solidification process. So an understanding of the settling characteristics is needed to predict the structure and segregation in castings. The settling velocity of NH4Cl equiaxed dendrites of non-spherical geometry was studied experimentally in an NH4Cl-70wt.%H2O solution. A calculation formula was proposed to calculate the settling velocity of sediment equiaxed dendrites in a tube filled with saturated solution at a moderate Reynolds number region. The retardation effects of the wall and morphology of the equiaxed dendrite on the settling velocity were taken into account in the development of the calculation formula, and the correction function B of the drag coefficient with consideration of the retardation effects of the wall and morphology of the equiaxed dendrite on the settling velocity of the equiaxed dendrite was calibrated according to the experimental results. A comparison showed that the formula has a good accordance with the experimental results.

关键词： equiaxed dendrite settling velocity morphology effect wall effect