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The transition from conservative to dissipative flows in class-B laser model with fold-Hopf bifurcation and coexisting attractors

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Chinese Physics B 2022年第6期31卷 39-45页

作者： Yue Li Zengqiang Chen Mingfeng Yuan Shijian Cang College of Artificial Intelligence Nankai UniversityTianjin 300350China Department of Earth and Space Science and Engineering York University4700 Keele StToronto M3J 1P3Canada Department of Product Design Tianjin University of Science and TechnologyTianjin 300222China

Dynamical behaviors of a class-B laser system with dissipative strength are analyzed for a model in which the polarization is adiabatically eliminated. The results show that the injected signal has an important effect on the dynamical behaviors of the system. When the injected signal is zero, the dissipative term of the class-B laser system is balanced with external interference, and the quasi-periodic flows with conservative phase volume appear. And when the injected signal is not zero, the stable state in the system is broken, and the attractors(period, quasi-period, and chaos) with contractive phase volume are generated. The numerical simulation finds that the system has not only one attractor, but also coexisting phenomena(period and period, period and quasi-period) in special cases. When the injected signal passes the critical value,the class-B laser system has a fold-Hopf bifurcation and exists torus “blow-up” phenomenon, which will be proved by theoretical analysis and numerical simulation.

关键词： conservative flows dissipative attractors coexisting phenomena fold-Hopf bifurcation class-Blaser chaotic system

Structure of Channel flows with Surface Mounted Ribs

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Journal of Thermal Science 2004年第3期13卷 213-219页

作者： Gérard J. POITRAS Laurent-Emmanuel BRIZZI Yves GAGNON Université de Moncton Moncton (NB) CanadaLaboratoire d'études aérodynamiques Université de Poitiers 86960 Futuroscope FranceUniversité de Moncton Edmundston (NB) Canada

The flow inside a channel with surface mounted ribs is studied by numerical simulation and experimental flow visualization. Both the geometry with one rib and the geometry with two ribs, placed perpendicular to the flow, are studied, with particular emphasis on the effect of the variation of the distance between the ribs on the structure of the flow. Results show that, for Reynolds number flows of 400 and 1000 (based on the uniform incoming velocity and the height of the ribs), the flow reattaches between the ribs when they are separated by distances of 12h (h being the height of the ribs) and 6h, respectively. In this respect, however, the numerical results for the Reynolds number flow of 1000 are in contradiction with published results.

关键词： vortex methods flow visualization channel flows ribs.

A numerical study for WENO scheme-based on different lattice Boltzmann flux solver for compressible flows

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Acta Mechanica Sinica 2018年第6期34卷 995-1014页

作者： You Li Xiao-Dong Niu Hai-Zhuan Yuan Adnan Khan Xiang Li College of Engineering Shantou UniversityShantou 515063China School of Mathematics and Computational Science Xiangtan UniversityXiangtan 411105China

In this paper,the finite difference weighted essentially non-oscillatory (WENO) scheme is incorporated into the recently developed four kinds of lattice Boltzmann flux solver (LBFS) to simulate compressible flows,including inviscid LBFS Ⅰ,viscous LBFS Ⅱ,hybrid LBFS Ⅲ and hybrid LBFS Ⅳ.Hybrid LBFS can automatically realize the switch between inviscid LBFS Ⅰ and viscous LBFS Ⅱ through introducing a switch *** resultant hybrid WENO-LBFS scheme absorbs the advantages of WENO scheme and hybrid *** investigate the performance of WENO scheme based on four kinds of LBFS *** results indicate that the devopled hybrid WENO-LBFS scheme has high accuracy,high resolution and no *** can not only accurately calculate smooth solutions,but also can effectively capture contact discontinuities and strong shock waves.

关键词： WENO scheme Hybrid Lattice Boltzmann flux solver Compressible inviscid flows Contact discontinuities Shock waves

Study of pollutant transport in depth-averaged flows using random walk method

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Journal of Hydrodynamics 2019年第2期31卷 303-316页

作者： Xue-fei Wu Dongfang Liang School of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China Department of Engineering University of CambridgeCambridgeUK

The random walk particle tracking(RWPT)method is compared with the Eulerian methods in investigating pollutant transport in depth-averaged *** a typical representative of the Eulerian model with high performance,the MacCormack scheme with Total Variation Diminishing modification(TVD-Mac)is selected for *** concentration is simulated in four case ***,both numerical models have been tested in two idealized cases and compared against analytical *** dissipation is observed for TVD-Mac model where the concentration changes abruptly,especially under the circumstances of low resolution and misalignment between the flow direction and grid *** the contrary,simulations by the random walk model achieve higher accuracy in both cases and are free of fictitious oscillations in the vicinity of sharp concentration ***,the solute oscillation along a one-dimensional hypothetical tidal estuary is simulated,with the RWPT accurately con serving mass and suffering less rm merical diffusion compared with the Eulerian ***,the process of pollutant transport in a Yangzte River reach is predicted by the *** longitudinal dispersion coefficient DL is calculated *** is compared favorably with the theoretical/empirical formulae,indicating the validity of the RWPT in solving complex natural problems.

关键词： Pollutant transport depth-averaged flows random walk particle tracking TVD-MacCormack

Predicting flows through microfluidic circuits with fluid walls

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Microsystems & Nanoengineering 2021年第6期7卷 119-127页

作者： Cyril Deroy Nicholas Stovall-Kurtz Federico Nebuloni Cristian Soitu Peter R.Cook Edmond J.Walsh Department of Engineering Science Osney Thermo-Fluids LaboratoryUniversity of OxfordOxford OX20ESUK Sir William Dunn School of Pathology University of OxfordOxford OX13REUK Cold Spring Harbor Laboratory Cold Spring HarborNYUSA

The aqueous phase in traditional microfluidics is usually confined by solid walls;flows through such systems are often predicted *** solid walls limit access,open systems are being developed in which the aqueous phase is partly bounded by fluid walls(interfaces with air or immiscible liquids).Such fluid walls morph during flow due to pressure gradients,so predicting flow fields remains *** recently developed a version of open microfluidics suitable for live-cell biology in which the aqueous phase is confined by an interface with an immiscible and bioinert fluorocarbon(FC40).Here,we find that common medium additives(fetal bovine serum,serum replacement)induce elastic no-slip boundaries at this interface and develop a semi-analytical model to predict flow *** experimentally validate the model’s accuracy for single conduits and fractal vascular trees and demonstrate how flow fields and shear stresses can be controlled to suit individual applications in cell biology.

关键词： walls flows flow

Influence of aeration and initial water thickness on axial velocity attenuation of jet flows

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第5期14卷 362-370页

作者： Wang-ru WEI Jun DENG Bin LIU State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Hydro-China Kunming Engineering Corporation

With the development of ski-jump energy dissipation for high and large discharge among the hydraulic projects,the effects of characteristics of water flow on energy dissipation are increasingly *** the present study,the effects of aeration and the initial water thickness on axial velocity attenuation of jet flow were analyzed,using variance analysis and numerical calculated *** the analysis of test data,both of the air concentration and initial water thickness are sensitive factors for the axial velocity attenuation of jet flow along the axial way,and there is no significant interaction effect between the aeration and initial water *** has a more significant effect on the axial velocity attenuation of jet *** the initial water thickness of jet flow can reduce the length of jet core,and make the initial position of axial velocity attenuation closer to the nozzle *** numerical calculation results show that aeration can contribute to the enhancement of entrainment ability of jet flow,which may improve the interaction between jet flow and *** ski-jump energy dissipation among the hydraulic projects,combining aeration with decreasing initial water thickness of jet flow is an effective way to enhance the rate of axial velocity attenuation.

关键词： Velocity Aeration Initial water thickness Jet flows

Radial Shocks in Advection-Dominated Accretion flows Around Black Holes

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Chinese Physics Letters 2001年第1期18卷 148-150页

作者： GU Wei-Min LU Ju-Fu Center for Astrophysics University of Science and Technology of ChinaHefei 230026 National Astronomical Observatories Chinese Academy of SciencesBeijing 100012 Department of Physics Xiamen UniversityXiamen 361005

We have solved the set of equations for advection-dominated accretion flows(ADAFs)around black holes,and found a new class of global solutions with standing radial ***α-X-type shocks may exist in flows when 0≤α<*** example solution is given explicitly,for whichα=0.01 andγ=*** shock position is R_(sh)=8.68R_(g),which is between the inner sonic point R_(s1)=3.88R_(g) and the outer sonic point R_(s2)=85.92R_(g).

关键词： flows outer explicitly

Evaluation of climate change effects on extreme flows in a catchment of western Iran

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Frontiers of Earth Science 2019年第3期13卷 523-534页

作者： Soheila SAFARYAN Mohsen TAVAKOLI Noredin ROSTAMI Haidar EBRAHEVH Department of Natural Resources Ilam UniversityDam 69315516Iran Department of Watershed Management Faculty of Natural Resources and Earth SciencesUniversity of KashanKashan ***Iran

Investigation of the relationship between catchment hydrology with climate is essential for understanding of the impact of future climate on hydrological extremes, which may cause frequent flooding, drought, and shortage of water supply. The purpose of this study is to investigate the effects of climate change on extreme flows in one of the subcatchments of the Ilam dam catchment, Iran. The changes in climate parameters were predicted using the outputs of HadCM3 model for up to the end of the current century in three time periods including 2020s, 2050s, and 2080s. For A2 scenario, increases of 1.09℃, 2.03℃, and 3.62℃, and for B2 scenario rises of 1.18℃, 1.84℃, and 2.55℃ have been predicted. The results suggest that for A2 scenario, the amount of precipitation would decrease by 12.63, 49.13, and 63.42 and for B2 scenario by 47.02,48.51, and 70.26 mm per year. Also the values of PET for A2 scenario would increase by 51.18, 101.47 and 108.71 and for B2 scenario by 60.09, 89.86, and 124.32 mm per year. The results of running the SWAT model revealed that the average annual runoff would decrease by 0.11, 0.41, and 0.61 m3/s and for B2 scenario by 0.39, 0.47, and 0.59 m3/s. The extreme flows were then analyzed by running WETSPRO model. According to the results, the amounts of low flows for A2 scenario will decrease by 0.02, 0.21 and 0.33 m^3/s and for B2 scenario by 0.19, 0.26 and 0.29 m^3/s in the 2020s, 2050s and 2080s, respectively. On the other hand, the results show an increase of peak flows by 11.5, 19.1 and 48.7 m^3/s in A2 scenario and 11.12, 25.93 and 48.1 m^3/s in B2 scenario, respectively. Overall, the results indicated that an increase in return period leads to elevated levels of high flows and diminished low flows.

关键词： climate change extreme flows Ilam dam watershed Iran

Weather induced subtidal flows through multiple inlets of an arctic microtidal lagoon

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Acta Oceanologica Sinica 2019年第3期38卷 1-16页

作者： Chunyan Li Kevin M.Boswell Nazanin Chaichitehrani Wei Huang Renhao Wu Department of Oceanography and Coastal Sciences College of the Coast and Environment Louisiana State University Department of Biological Sciences Florida International University Horn Point Laboratory Center for Environmental Science University of Maryland College of Marine Sciences and Technology Zhejiang Ocean University

Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R^2 value ～96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is c

关键词： wind-driven flows multiple inlets micro-tidal numerical model experiments counter-wind flows quasi-steady state