期刊文献+
共找到23篇文章
< 1 2 >
每页显示 20 50 100
EFFECTS OF INCOMING FLOW ASYMMETRY ON SHOCK TRAIN STRUCTURES IN CONSTANT-AREA ISOLATORS 被引量:2
1
作者 王成鹏 张堃元 程克明 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2006年第1期1-7,共7页
To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the i... To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the isolator are investigated using wall static and pitot pressure measurements. Three incoming Mach numbers are considered as 1.5, 1.8 and 2. Results show that the increase of the asymmetry of the flow at the isolator entrance leads to the increase of the shock train length in the isolator for a given pressure ratio. Based on the analysis of the flow asymmetry effect at the isolator entrance on the shock train length, a modified correlation is proposed to calculate the length of the shock train. Predicted results of the proposed correlation are in good agreement with the experimental data. 展开更多
关键词 asymmetric supersonic flow shock train isolator design SCRAMJET wind tunnel test
下载PDF
Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species
2
作者 Jian-Feng Huang Clive T.Darwell Yan-Qiong Peng 《Plant Diversity》 SCIE CAS CSCD 2024年第2期181-193,共13页
Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where p... Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene flow.Signatures of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales. 展开更多
关键词 HYBRIDIZATION Heterospecific visitation FIG Pollinator wasp Asymmetric gene flow
下载PDF
Mobile bed thickness in skewed asymmetric oscillatory sheet flows 被引量:6
3
作者 Xin Chen Yong Li Fujun Wang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2018年第2期257-265,共9页
A new instantaneous mobile bed thickness model is presented for sediment transport in skewed asymmetric oscillatory sheet flows. The proposed model includes a basic bed load part and a suspended load part related to t... A new instantaneous mobile bed thickness model is presented for sediment transport in skewed asymmetric oscillatory sheet flows. The proposed model includes a basic bed load part and a suspended load part related to the Shields parameter, and takes into account the effects of mass conservation, phase-lag, and asymmetric boundary layer development, which are important in skewed asymmetric flows but usually absent in classical models. The proposed model is validated by erosion depth and sheet flow layer thickness data in both steady and unsteady flows, and applied to a new instantaneous sediment transport rate formula. With higher accuracy than classical empirical models in steady flows, the new formula can also be used for instantaneous sediment transport rate prediction in skewed asymmetric oscillatory sheet flows. 展开更多
关键词 Mobile bed thickness PHASE-LAG Sediment transport Sheet flow Skewed asymmetric oscillatory flow
下载PDF
EXPERIMENTAL STUDY ON TURBULENT FEATURES IN THE NEGATIVE TRANSPORT REGION OF ASYMMETRIC PLANE CHANNEL FLOW 被引量:4
4
作者 卢志明 刘宇陆 蒋剑波 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2001年第2期125-132,共8页
Turbulent features of streamwise and vertical components of velocity in the negative transport region of asymmetric plane channel flow have been studied experimentally in details. Experiments show that turbulent fluct... Turbulent features of streamwise and vertical components of velocity in the negative transport region of asymmetric plane channel flow have been studied experimentally in details. Experiments show that turbulent fluctuations in negative transport region are suppressed, and their probability distributions are far from Gaussian. Besides, the skewness factors attain their negative maxima at the position of the maximum mean velocity, whereas the flatness factors attain their positive maxima at the same position. 展开更多
关键词 negative transport asymmetric channel flow turbulent characteristics
下载PDF
Numerical investigations of asymmetric flow of a micropolar fluid between two porous disks 被引量:4
5
作者 Muhammad Ashraf M.Anwar Kamal K.S.Syed 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2009年第6期787-794,共8页
Numerical solution is presented for the two- dimensional flow of a micropolar fluid between two porous coaxial disks of different permeability for a range of Reynolds number Re (-300≤ Re 〈 0) and permeability para... Numerical solution is presented for the two- dimensional flow of a micropolar fluid between two porous coaxial disks of different permeability for a range of Reynolds number Re (-300≤ Re 〈 0) and permeability parameter A (1.0≤A ≤2.0). The main flow is superimposed by the injection at the surfaces of the two disks. Von Karman's similarity transformations are used to reduce the governing equations of motion to a set of non-linear coupled ordinary differential equations (ODEs) in dimensionless form. An algorithm based on the finite difference method is employed to solve these ODEs and Richardson's extrapolation is used to obtain higher order accuracy. The results indicate that the parameters Re and A have a strong influence on the velocity and microrotation profiles, shear stresses at the disks and the position of the viscous/shear layer. The micropolar material constants cl, c2, c3 have profound effect on microrotation as compared to their effect on streamwise and axial velocity profiles. The results of micropolar fluids are compared with the results for Newtonian fluids. 展开更多
关键词 Porous disks . Asymmetric flow .Micropolar fluid . Finite differences.Viscous layer
下载PDF
Homotopy analysis solutions for the asymmetric laminar flow in a porous channel with expanding or contracting walls 被引量:7
6
作者 X.-H. Si L.-C. Zheng +1 位作者 X.-X. Zhang Y. Chao 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2011年第2期208-214,共7页
In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homot... In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method (HAM) is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail. 展开更多
关键词 Homotopy analysis method · Expanding or contracting wall · Asymmetric laminar flow · Porous channel · Expansion ratio
下载PDF
A numerical study for boundary layer current and sheet flow transport induced by a skewed asymmetric wave 被引量:1
7
作者 CHEN Xin ZHANG Zichao WANG Fujun 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第9期82-89,共8页
An analytical model with essential parameters given by a two-phase numerical model is utilized to study the net boundary layer current and sediment transport under skewed asymmetric oscillatory sheet flows. The analyt... An analytical model with essential parameters given by a two-phase numerical model is utilized to study the net boundary layer current and sediment transport under skewed asymmetric oscillatory sheet flows. The analytical model is the first instantaneous type model that can consider phase-lag and asymmetric boundary layer development. The two-phase model supplies the essential phase-lead, instantaneous erosion depth and boundary layer development for the analytical model to enhance the understanding of velocity skewness and acceleration skewness in sediment flux and transport rate. The sediment transport difference between onshore and offshore stages caused by velocity skewness or acceleration skewness is shown to illustrate the determination of net sediment transport by the analytical model. In previous studies about sediment transport in skewed asymmetric sheet flows, the generation of net sediment transport is mainly concluded to the phase-lag effect.However, the phase-lag effect is shown important but not enough for the net sediment transport, while the skewed asymmetric boundary layer development generated net boundary layer current and mobile bed effect are key important in the transport process. 展开更多
关键词 analytical model boundary layer current sediment transport sheet flow skewed asymmetric wave
下载PDF
Asymptotic solutions for the asymmetric flow in a channel with porous retractable walls under a transverse magnetic field
8
作者 Hongxia GUO Ping LIN Lin LI 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第8期1147-1164,共18页
The self-similarity solutions of the Navier-Stokes equations are constructed for an incompressible laminar flow through a uniformly porous channel with retractable walls under a transverse magnetic field. The flow is ... The self-similarity solutions of the Navier-Stokes equations are constructed for an incompressible laminar flow through a uniformly porous channel with retractable walls under a transverse magnetic field. The flow is driven by the expanding or contracting walls with different permeability. The velocities of the asymmetric flow at the upper and lower walls are different in not only the magnitude but also the direction. The asymptotic solutions are well constructed with the method of boundary layer correction in two cases with large Reynolds numbers, i.e., both walls of the channel are with suction, and one of the walls is with injection while the other one is with suction. For small Reynolds number cases, the double perturbation method is used to construct the asymptotic solution. All the asymptotic results are finally verified by numerical results. 展开更多
关键词 laminar flow asymmetric flow asymptotic solution porous and retractable channel magnetic field
下载PDF
Bifurcation phenomena and control for magnetohydrodynamic flows in a smooth expanded channel
9
作者 G.C.Layek Mani Shankar Mandal H.A.Khalaf 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第11期374-383,共10页
This work reports the effects of magnetic field on an electrically conducting fluid with low electrical conductivity flowing in a smooth expanded channel. The governing nonlinear magnetohydrodynamic (MHD) equations ... This work reports the effects of magnetic field on an electrically conducting fluid with low electrical conductivity flowing in a smooth expanded channel. The governing nonlinear magnetohydrodynamic (MHD) equations in induction- free situations are derived in the framework of MHD approximations and solved numerically using the finite-difference technique. The critical values of Reynolds number (based on upstream mean velocity and channel height) for symmetry breaking bifurcation for a sudden expansion channel (1:4) is about 36, whereas the value in the case of the smooth expansion geometry used in this work is obtained as 298, approximately (non-magnetic case). The flow of an electrically conducting fluid in the presence of an externally applied constant magnetic field perpendicular to the plane of the flow is reduced significantly depending on the magnetic parameter (M). It is expansion (1:4) is about 475 for the magnetic parameter M found that the critical value of Reynolds number for smooth = 2. The separating regions developed behind the smooth symmetric expansion are decreased in length for increasing values of the magnetic parameter. The bifurcation diagram is shown for a symmetric smoothly expanding channel. It is noted that the critical values of Reynolds number increase with increasing magnetic field strength. 展开更多
关键词 weakly electrically conducting fluid flow bifurcation asymmetric flow smooth expansion
下载PDF
NUMERICAL INVESTIGATION OF THE MECHANISM OF ASYMMETRIC VORTEX FLOWS
10
作者 Zhang Wu (Department of Mechanics,Peking University)Luo Shijun (Dept.of Mechanical Engng.,Northwestern Polytech,Univ.,Xian) 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1990年第4期311-315,共5页
A robust iterative method suitable for the numerical simulation of high angle-of-attack vortex flows is established based upon the multiple line-vortex model(MLVM).With symmetric or asymmetric positions of sep- aratio... A robust iterative method suitable for the numerical simulation of high angle-of-attack vortex flows is established based upon the multiple line-vortex model(MLVM).With symmetric or asymmetric positions of sep- aration lines given,the first converged solution at an angle of attack as high as 60 degree is obtained by means of the present method.Numerical experiments for a tangent-ogive forebody indicate the viscous onset mechanism of asymmetric vortex flows over a body of revolution at high angles of attack and zero sideslip. 展开更多
关键词 asymmetric vortex flow viscous mechanism multiple line-vortex model numerical investigation
下载PDF
Evolutionary history of a desert perennial Arnebia szechenyi(Boraginaceae):Intraspecific divergence,regional expansion and asymmetric gene flow
11
作者 Meng-Jiao Fu Hai-Yang Wu +1 位作者 Dong-Rui Jia Bin Tian 《Plant Diversity》 SCIE CAS CSCD 2021年第6期462-471,共10页
The complex interactions of historical,geological and climatic events on plant evolution have been an important research focus for many years.However,the role of desert formation and expansion in shaping the genetic s... The complex interactions of historical,geological and climatic events on plant evolution have been an important research focus for many years.However,the role of desert formation and expansion in shaping the genetic structures and demographic histories of plants occurring in arid areas has not been well explored.In the present study,we investigated the phylogeography of Arnebia szechenyi,a desert herb showing a near-circular distribution surrounding the Tengger Desert in Northwest China.We measured genetic diversity of populations using three maternally inherited chloroplast DNA(cpDNA)fragments and seven bi-paternally inherited nuclear DNA(nDNA)loci that were sequenced from individuals collected from 16 natural populations across its range and modelled current and historical potential habitats of the species.Our data indicated a considerably high level of genetic variation within A.szechenyi and noteworthy asymmetry in historical migration from the east to the west.Moreover,two nuclear genetic groups of populations were revealed,corresponding to the two geographic regions separated by the Tengger Desert.However,analysis of cpDNA data did not show significant geographic structure.The most plausible explanation for the discrepancy between our findings based on cpDNA and nDNA data is that A.szechenyi populations experienced long periods of geographic isolation followed by range expansion,which would have promoted generalized recombination of the nuclear genome.Our findings further highlight the important role that the Tengger Desert,together with the Helan Mountains,has played in the evolution of desert plants and the preservation of biodiversity in arid Northwest China. 展开更多
关键词 Asymmetric gene flow Cytonuclear discordance Desert growth Intraspecific divergence
下载PDF
Vortex Rossby Waves in Asymmetric Basic Flow of Typhoons
12
作者 Tianju WANG Zhong ZHONG Ju WANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2018年第5期531-539,共9页
Wave ray theory is employed to study features of propagation pathways(rays) of vortex Rossby waves in typhoons with asymmetric basic flow, where the tangential asymmetric basic flow is constructed by superimposing t... Wave ray theory is employed to study features of propagation pathways(rays) of vortex Rossby waves in typhoons with asymmetric basic flow, where the tangential asymmetric basic flow is constructed by superimposing the wavenumber-1 perturbation flow on the symmetric basic flow, and the radial basic flow is derived from the non-divergence equation. Results show that, in a certain distance, the influences of the asymmetry in the basic flow on group velocities and slopes of rays of vortex Rossby waves are mainly concentrated near the radius of maximum wind(RMW), whereas it decreases outside the RMW. The distributions of radial and tangential group velocities of the vortex Rossby waves in the asymmetric basic flow are closely related to the azimuth location of the maximum speed of the asymmetric basic flow, and the importance of radial and tangential basic flow on the group velocities would change with radius. In addition, the stronger asymmetry in the basic flow always corresponds to faster outward energy propagation of vortex Rossby waves. In short, the group velocities, and thereby the wave energy propagation and vortex Rossby wave ray slope in typhoons, would be changed by the asymmetry of the basic flow. 展开更多
关键词 asymmetric basic flow vortex Rossby waves group velocity propagation pathways wave ray
下载PDF
Asymmetric breakup of a droplet in an axisymmetric extensional flow
13
作者 Dongming Yu Manman Zheng +1 位作者 Taoming Jin Jingtao Wang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第1期63-70,共8页
The asymmetric breakups of a droplet in an axisymmetric cross-like microfluidic device are investigated by using a three-dimensional volume of fluid(VOF) multiphase numerical model. Two kinds of asymmetries(droplet lo... The asymmetric breakups of a droplet in an axisymmetric cross-like microfluidic device are investigated by using a three-dimensional volume of fluid(VOF) multiphase numerical model. Two kinds of asymmetries(droplet location deviation from the symmetric geometry center and different flow rates at two symmetric outlets) generate asymmetric flow fields near the droplet, which results in the asymmetric breakup of the latter. Four typical breakup regimes(no breakup, one-side breakup, retraction breakup and direct breakup) have been observed.Two regime maps are plotted to describe the transition from one regime to another for the two types of different asymmetries, respectively. A power law model, which is based on the three critical factors(the capillary number,the asymmetry of flow fields and the initial volume ratio), is employed to predict the volume ratio of the two unequal daughter droplets generated in the direct breakup. The influences of capillary numbers and the asymmetries have been studied systematically in this paper. The larger the asymmetry is, the bigger the oneside breakup zone is. The larger the capillary number is, the more possible the breakup is in the direct breakup zone. When the radius of the initial droplet is 20 μm, the critical capillary numbers are 0.122, 0.128, 0.145,0.165, 0.192 and 0.226 for flow asymmetry factor AS= 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5, respectively, in the flow system whose asymmetry is generated by location deviations. In the flow system whose asymmetry is generated by two different flow rates at two outlets, the critical capillary numbers are 0.121, 0.133, 0.145, 0.156 and 0.167 for AS= 1/21, 3/23, 1/5, 7/27 and 9/29, respectively. 展开更多
关键词 Asymmetric breakup Droplet Volume of fluid method Axisymmetric extensional flow
下载PDF
Analytical and Computational Analysis of Flow Splitting in Multiple, Parallel Channels Systems
14
作者 Alejandro I. Lazarte J. C. Ferreri 《World Journal of Nuclear Science and Technology》 2016年第3期170-190,共22页
Previous analytical results on flow splitting are generalized to consider multiple boiling channels systems. The analysis is consistent with the approximations usually adopted in the use of systems codes (like RELAP5 ... Previous analytical results on flow splitting are generalized to consider multiple boiling channels systems. The analysis is consistent with the approximations usually adopted in the use of systems codes (like RELAP5 and TRACE5, among others) commonly applied to perform safety analyses of nuclear power plants. The problem is related to multiple, identical, parallel boiling channels, connected through common plena. A theoretical model limited in scope explains this flow splitting without reversal. The unified analysis performed and the confirmatory computational results found are summarized in this paper. New maps showing the zones where this behavior is predicted are also shown considering again twin pipes. Multiple pipe systems have been found not easily amenable for analytical analysis when dealing with more than four parallel pipes. However, the particular splitting found (flow along N pipes dividing in one standalone pipe flow plus N -1 identical pipe flows) has been verified up to fourteen pipes, involving calculations in systems with even and odd number of pipes using the RELAP5 systems thermal-hydraulics code. 展开更多
关键词 Multiple Parallel Boiling Channels Systems Asymmetric Splitting flow Verification of Codes Systems Thermal-Hydraulics Codes Nuclear Engineering
下载PDF
Effects of tip perturbation and wing locations on rolling oscillation induced by forebody vortices 被引量:8
15
作者 Bing Wang Xue-Ying Deng Bao-Feng Ma Zhen Rong 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2010年第5期787-791,共5页
The wing rock motion is frequently suffered by a wing-body configuration with low swept wing at high angle of attack. It is found from our experimental study that the tip perturbation and wing longitudinal locations a... The wing rock motion is frequently suffered by a wing-body configuration with low swept wing at high angle of attack. It is found from our experimental study that the tip perturbation and wing longitudinal locations affect significantly the wing rock motion of a wing-body. The natural tip perturbation would make the wing rock motion of a nondeterministic nature and an artificial mini-tip perturbation would make the wing rock motion deterministic. The artificial tip perturbation would, as its circumferential location is varied, generate three different types of motion patterns: (1) limit cycle oscillation, (2) irregular oscillation, (3) equilibrium state with tiny oscillation. The amplitude of rolling oscillation corresponding to the limit cycle oscillatory motion pattern is decreased with the wing location shifting downstream along the body axis. 展开更多
关键词 Wing rock motion- Asymmetric vortices flow High angle of attack aerodynamics Nose tip perturbation
下载PDF
Asymmetric flow effect in a horizontal natural ventilated tunnel with different aspect ratios under the influence of longitudinal fire locations 被引量:4
16
作者 Longxing Yu Huaxian Wan Jie Ji 《Building Simulation》 SCIE EI CSCD 2021年第4期1311-1323,共13页
This paper has analyzed the asymmetric flow effect of fire-induced thermal flow in a horizontal tunnel under the natural ventilation condition by conducting large eddy simulations (LES). The key objective is to reveal... This paper has analyzed the asymmetric flow effect of fire-induced thermal flow in a horizontal tunnel under the natural ventilation condition by conducting large eddy simulations (LES). The key objective is to reveal and to have a better understanding of the asymmetric flow effect caused by the upstream and downstream tunnel length difference. The mechanism behind it can be explained based on the conservation of mass and dynamic force analysis on the smoke and fresh air. The strength of the asymmetric flow effect is characterized by the mass flow rate of the induced longitudinal flow (net mass flow rate of a cross-section). An empirical correlation to predict the induced longitudinal mass flow rate is proposed. Furthermore, the law of smoke and air flow distribution within a horizontal tunnel is established. The proportion of smoke (or air) flowing out (or coming in) through the opening increase (or decrease) linearly with the increasing distance between that opening to the fire location. The variation of the air flow with the longitudinal fire location in a tunnel is more sensitive than the smoke flow. Results have shown that as the fire approaches the tunnel exit from the middle of the tunnel, the smoke spilling out through this opening is reduced from 50% to 40%, while the fresh air incoming from this opening is increased from 50% to 100% and vice versa. 展开更多
关键词 asymmetric flow effect fire location thermal flow SMOKE tunnel fire CFD
原文传递
Unsteady cooperative flow in compression system 被引量:2
17
作者 Sheng Zhou Yajun Lu +2 位作者 Anping Hou Wei Yuan Zhiping Li 《Propulsion and Power Research》 SCIE 2012年第1期12-28,共17页
When there are several bodies with relative motion in a flow field,such as the flow in the compression system of modern aero-engine,the flow field will have certain special features,one of which is that the time-space... When there are several bodies with relative motion in a flow field,such as the flow in the compression system of modern aero-engine,the flow field will have certain special features,one of which is that the time-space structure of such multi-bodies unsteady vorticity flow field would be either of unsteady natural flow(UNF)pattern or of unsteady cooperative flow(UCF)pattern.If we further examine the aerodynamic design system of aero-engine,there is no mechanism for the unsteady cooperative flow to occur,in other words the flow field must be of the unsteady natural flow type.If certain technical measures can be adopted to transform UNF into UCF,the aerodynamic performances will surely be improved.This is the main task the author and their colleague have been devoted to and the results are reviewed in the present paper with emphases laid on basic ideas,technical approaches and experimental verifications. 展开更多
关键词 Unsteady cooperative flow Unsteady natural flow Time-space structure of the flow field Compression system AERO-ENGINE flow over multibodies Asymmetric flow Axial compressor transonic flow
原文传递
Study on asymmetric interior corner flow in microgravity condition 被引量:3
18
作者 LI JingHao CHEN XiaoQian +1 位作者 HUANG YiYong BAI YuZhu 《Science China(Technological Sciences)》 SCIE EI CAS 2012年第8期2332-2337,共6页
The capillary flow in asymmetric interior corner consisting of straight vane and curved wall is studied with analytical solution.The concept of equivalent interior corner angle is proposed to convert the asymmetric in... The capillary flow in asymmetric interior corner consisting of straight vane and curved wall is studied with analytical solution.The concept of equivalent interior corner angle is proposed to convert the asymmetric interior corner model into symmetric interior corner model.Then the governing equations of interior corner flow are established,and based on which the interior corner flow is calculated.This method is used to analyze the capillary flow in cylindrical vane-type surface tension tank with outer vanes.The research can provide beneficial reference to the design of vane-type surface tension tank. 展开更多
关键词 asymmetric interior corner flow equivalent interior corner angle vane-type surface tension tank analytical solution
原文传递
Characteristics of the Asymmetric Flow of Tropical Cyclone Shanshan(2006) During Its Turning and Intensification Period
19
作者 孙源 钟中 土元 《Acta meteorologica Sinica》 SCIE 2012年第2期147-162,共16页
In this paper,characteristics of the asymmetric flow of Tropical Cyclone(TC) Shanshan(2006) during its turning and intensification period over the oceanic area east of Taiwan are investigated,based on the simulati... In this paper,characteristics of the asymmetric flow of Tropical Cyclone(TC) Shanshan(2006) during its turning and intensification period over the oceanic area east of Taiwan are investigated,based on the simulation results from the nonhydrostatic mesoscale model WRF(Weather Research and Forecasting).It is found that the symmetric flow strengthened as the TC intensified,whereas the amplitude of the asymmetric flow of wavenumber 2 increased more significantly,which was strong enough to be comparable with or even exceed that of wavenumber 1,becoming the main part of the asymmetric flow sometimes.The asymmetric waves rotated around the TC center mainly counterclockwise.The closer to the center,the faster the asymmetric waves rotated.Moreover,the asymmetric flow rotated rapidly(slowly) during the slow(rapid) intensification of the TC,and the radial wavenumber showed an increase during the TC intensification.Furthermore,because of the superposition of intensified symmetric flow with the positive perturbation of the asymmetric flow,the maximum wind speed of TC Shanshan became larger.During the merger of the double eyewalls of Shanshan,the symmetric flow showed less increase in strength and the intensification of maximum wind speed was mainly related to the energy accumulation caused by the phase change of the asymmetric waves.The energy accumulation was realized when the asymmetric waves altered the strength and distribution of the inner and outer maximum wind cores,leading to the combination of the inner and outer eyewalls and eventually resulting in the intensification of the TC. 展开更多
关键词 tropical cyclone INTENSITY asymmetric flow phase EYEWALL
原文传递
A novel architecture of electro-hydrostatic actuator with digital distribution 被引量:5
20
作者 Jing YAO Pei WANG +2 位作者 Zhaosheng DONG Dongting JIANG Tong SHA 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2021年第5期224-238,共15页
To address the flow imbalance rapidly of the asymmetric Electro-Hydrostatic Actuator(EHA),this paper presents a novel architecture of asymmetric EHA with the Digital Distribution(EHA-DD).It also improves the flow nonl... To address the flow imbalance rapidly of the asymmetric Electro-Hydrostatic Actuator(EHA),this paper presents a novel architecture of asymmetric EHA with the Digital Distribution(EHA-DD).It also improves the flow nonlinearity and control accuracy of the pump,especially in the low-speed condition.The digital distribution with two High-Speed on–off Valves(HSVs)not only balances flow instead of the check valves,but also replaces the pump at the low-speed to control output flow by adjusting the PWM signal.The pump and HSVs are the crucial components to control flow output.Firstly,the flow calculation models of the pump and the duty ratio inversed model of the HSV are obtained through experimental tests and the identification method.To get the control input signal for the required flow,the pump speed and PWM duty ratio for the HSVs are inversed to compensate for flow output.Further,a multimode digital flow distribution control method based on pump speed,mainly including the pump-controlled mode for large flow demand and valve-controlled mode for little flow demand,is proposed to control the accurate flow output actively.The step extension experiments based on the flow calculation models are conducted on the EHA-DD prototype under elastic,opposite varying load.The results demonstrate that the EHADD realizes little position error by accurate flow control,and it is also beneficial to improve the service life of the pump. 展开更多
关键词 asymmetrical flow Digital distribution EHA High-speed on–off valve NONLINEARITY PWM control
原文传递
上一页 1 2 下一页 到第
使用帮助 返回顶部