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Wing Kinematics, Aerodynamic Forces and vortex-wake Structures in Fruit-flies in Forward Flight

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Journal of Bionic Engineering 2016年第3期13卷 478-490页

作者： XueguangMeng Mao Sun Institute of Fluid Mechanics Beijing University of Aeronautics and Astronautics Beijing 100191 China

Wing kinematics in forward-flying fruit-flies was measured using high-speed cameras and flows of the flapping wing were calculated numerically. The large lift and thrust coefficients produced by the wing were explained. The wing flaps along a forward-tilting stroke plane. In the starting portion of a half-stroke （an upstroke or downstroke）, the wing pitches down to a small pitch angle; during the mid portion （the wing has built up its speed）, it first fast pitches up to a large pitch angle and then maintains the pitch angle; in the ending portion, the wing pitches up further. A large aerodynamic force （normal to the wing surface） is produced during the mid portion of a half-stroke. The large force is produced by the fast-pitching-up rotation and delayed-stall mechanisms. As a result of the orientation of wing, the thrust that propels the insect is produced by the upstroke and the major part of the vertical force that supports the weight is produced by the downstroke. In producing the thrust the upstroke leaves a ＂vortex ring＂ that is almost vertical, and in producing the vertical force the downstroke leaves a ＂vortex ring＂ that is almost horizontal.

关键词： fruit-fly wing kinematics forward flight Navier-Stokes simulation vortex

Tunable parity-time symmetry vortex laser from a phase change material-based microcavity

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Microsystems & Nanoengineering 2023年第6期9卷 273-280页

作者： Ying Su Hongji Fan Shitong Zhang Tun Cao School of Optoelectronic Engineering and Instrumentation Science Dalian University of TechnologyDalian 116024China School of Science and Letters UC Davis21005th StDavisCA 95618USA

Traditional light sources cannot emit an electromagnetic(EM)field with an orbital angular momentum(OAM),limiting their applications in modern *** recent development of the OAM laser,mainly based on micro-and nanostructures,can satisfy the increasing requirements for on-chip photonics and information ***,the photonic structures have fixed parameters that prevent these OAM lasers from being dynamically ***,we propose tunable vortex lasing from a microring cavity integrated by a phase change material,Ge_(2)Sb_(2)Te_(5)(GST225).By modulating the complex refractive index to create an exceptional point(EP)to break the degeneracy of whispering gallery modes with opposite orientations,the microlaser working at the EP can impart an artificial angular momentum,thus emitting vortex beams with well-defined *** grating scatter on the edge of the microring can provide efficient vertical *** vortex laser wavelength from the GST225/InGaAsP dual-layered microring cavity can be dynamically tuned by switching the state of GST225 between amorphous and crystalline without changing the microring *** construct an electric-thermal model to show the tuning range of operating wavelengths(EPs)from 1544.5 to 1565.9 nm in~25 *** study on high-speed tunable PT-symmetry vortex lasers facilitates the next generation of integrated optoelectronic devices for optical computing and communications in both classical and quantum regions.

关键词： tuning symmetry vortex

Dynamic evolution of vortex structures induced bytri-electrode plasma actuator

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Chinese Physics B 2020年第2期29卷 337-345页

作者： Bo-Rui Zheng Ming Xue Chang Ge School of Automation and Information Engineering Xi'an University of TechnologyXi'an 710048China Department of Aeronautics and Astronautics Northwestern Polytechnical UniversityXi'an 710072China

Plasma flow control is a new type of active flow control approach based on plasma pneumatic *** barrier discharge(DBD) actuators have become a focus of international aerodynamic ***,the practical applications of typical DBDs are largely restricted due to their limited discharge area and low relative-induced *** further improvement of performance will be beneficial for engineering *** this paper,high-speed schlieren and high-speed particle image velocimetry(PIV) are employed to study the flow field induced by three kinds of plasma actuations in a static atmosphere,and the differences in induced flow field structure among typical DBD,extended DBD(EX-DBD),and tri-electrode sliding discharge(TED) are *** analyzing of the dynamic evolution of the maximum horizontal velocity over time,the velocity profile at a fixed horizontal position,and the momentum and body force in a control volume reveals that the induced velocity peak value and profile velocity height of EX-DBD are higher than those of the other two types of actuation,suggesting that EX-DBD actuation has the strongest temporal aerodynamic effect among the three types of *** TED actuation not only can enlarge the plasma extension but also has the longest duration in the entire pulsed period and the greatest influence on the height and width of the airflow near the wall ***,the TED actuation has the ability to continuously influencing a larger three-dimensional space above the surface of the nlasma actuator.

关键词： plasma flow control dielectric barrier discharge vortex dynamics tri-electrode sliding discharge

A Model of High-Speed Endovascular Sonothrombolysis with vortex Ultrasound-Induced Shear Stress to Treat Cerebral Venous Sinus Thrombosis

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Research 2023年第1期2023卷 1-13页

作者： Bohua Zhang Huaiyu Wu Howuk Kim Phoebe J.Welch Ashley Cornett Greyson Stocker Raul G.Nogueira Jinwook Kim Gabe Owens Paul A.Dayton Zhen Xu Chengzhi Shi Xiaoning Jiang Department of Mechanical&Aerospace Engineering North Carolina State UniversityRaleighNCUSA Department of Mechanical Engineering Inha University IncheonRepublic of Korea George W.Woodruff School of Mechanical Enginering Grgia lnstitute of TechnlogyAtlantaGAUSA Department of Biomedical Engineering University of Michigan Ann ArborMIUSA Department of Neurology Universityof Pittsburgh Medical CenterPttsburghPA USA Department of Biomedical Engineering University of North CarolinaChapel HillNCUSA Parker H.Petit Institute for Bioengineering and Bioscience Georgia Institute of TechnologyAtlantaGAUSA

This research aims to demonstrate a novel vortex ultrasound enabled endovascular thrombolysis method designed for treating cerebral venous sinus thrombosis(CVST).This is a topic of substantial importance since current treatment modalities for CVST still fail in as many as 20%to 40%of the cases,and the incidence of CvST has increased since the outbreak of the coronavirus disease 2019 *** with conventional anticoagulant or thrombolytic drugs,sonothrombolysis has the potential to remarkably shorten the required treatment time owing to the direct clot targeting with acoustic ***,previously reported strategies for sonothrombolysis have not demonstrated clinically meaningful outcomes(e.g.,recanalization within 30 min)in treating large,completely occluded veins or ***,we demonstrated a new vortex ultrasound technique for endovascular sonothrombolysis utilizing wavematter interaction-induced shear stress to enhance the lytic rate *** in vitro experiment showed that the lytic rate was increased by at least 64.3%compared with the nonvortex endovascular ultrasound treatment.A 3.1-g,7.5-cm-long,completely occluded in vitro 3-dimensional model of acute CVST was fully recanalized within 8 min with a record-high lytic rate of 237.5 mg/min for acute bovine clot ***,we confirmed that the vortex ultrasound causes no vessel wall damage over ex vivo canine *** vortex ultrasound thrombolysis technique potentially presents a new life-saving tool for severe CVST cases that cannot be efficaciously treated using existing therapies.

关键词： thrombolysis drugs vortex

Optical Torque Exerted on a Rotator under Illumination of a vortex Beam

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Chinese Physics Letters 2012年第6期29卷 145-148页

作者： LI Dong-Hua PU Ji-Xiong WANG Xi-Qing College of Information Science&Engineering Huaqiao UniversityXiamen 361021 College of Physical Science and Technology Southwest Jiaotong UniversityChengdu 610031

We investigate the torque on a specially shaped rotator produced by a vortex *** formulas for the torque along x,y and z directions axe derived,and numerical calculation is *** is found that for the specially shaped rotator,the torque brought by the Laguerre-Gauss (LG) vortex beam is dependent upon the angle of the facet for each part of the rotator,and the topological charge of the vortex *** is shown that torque is generated from both the light momentum and orbital angular momentum (OAM) of the incident vortex beam,indicating that we can control the rotation of the rotator by modulating the OAM of the incident light beam.

关键词： vortex momentum shaped

Exact vortex Clusters of Two-Dimensional Quantum Fluid with Harmonic Confinement

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Chinese Physics Letters 2013年第4期30卷 14-17页

作者： CHONG Gui-Shu ZHANG Ling-Ling HAI Wen-Hua School of Physics and Microelectronics Hunan UniversityChangsha 410082 Department of Physics and Key Laboratory of Low-Dimensional Quantum Structure and Quantum Control of Ministry of Education Hunan Normal UniversityChangsha 410081

A family of exact analytical solutions of vortices in quantum fluid governed by a two-dimensional time-dependent Schr?dinger equation is presented,which describes different kinds of vortex *** dynamics of different vortex clusters,such as the single vortex,vortex pair,vortex dipole and vortex trimer in a two-dimensional quantum fluid are analytically studied based on these exact *** time evolutions of the wave of such vortices are demonstrated,and the orbits of motion of singular points in the vortices are also *** interactions of vortices in many-vortex clusters are discussed.A repulsive interaction between vortices with the same topological charge,and inter-annihilation and inter-creation of vortices with opposite topological charge,are shown.

关键词： vortex exact topological

Objective Omega vortex identification method

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Journal of Hydrodynamics 2019年第3期31卷 455-463页

作者： Jian-ming Liu Yi-sheng Gao Yi-qian Wang Chaoqun Liu School of Mathematics and Statistics Jiangsu Normal University Xuzhou 221116 China Department of Mathematics University of Texas at Arlington Arlington 76019 Texas USA School of Aerospace Engineering Tsinghua University Beijing 100084 China

A new vortex identification method (Liu et al. 2016) was proposed to represent the rotation relative strength and capture and visualize the vortices in our previous study. The basic idea of the Ω method is that a ratio of the vorticity squared over the summation of the vorticity squared and the deformation squared should be used to measure the relative rotation strength. However, the vorticity tensor norm is not objective. Thus, a moving observer will observe different vortex structures in a moving reference frame, which will make confusions about the real vortex structures. In the present study, by the definitions of the net spin tensor and the net vorticity vector, an objective Ω vortex identification method is presented with examples to verify that the vortex structures retain in a moving reference frame.

关键词： vortex identification the Ω method objectivity turbulence visualization turbulence

Dynamic Behaviour of vortex Matter, Memory Effect and Mittag--Leffler Relaxation

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Chinese Physics Letters 2001年第2期18卷 269-271页

作者： LIU Gang HAN Ru-Shan Department of Physics Peking UniversityBeijing 100871 China Institute of Atomic Energy P.O.Box 275(18)Beijing 102413

Using fractional Fokker-Planck equation and Langevin equation's Monte Carlo simulation,we find that when current density is less than critical current density,at the very beginning the motion for vortices is mainly within the pinning well with the typical relaxation time *** time t is longer than Tr,the vortex glass will distort between two adjacent pining wells and will lead to memory effect which is lacking in the Mott insulator and pancake *** inertial effect is not dominating as compared with the formation and growth of easy-flow *** random quenched disorder will lead to Mittag-Leffler relaxation.

关键词： equation relaxation vortex

Galilean invariance of Omega vortex identification method

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Journal of Hydrodynamics 2019年第2期31卷 249-255页

作者： Jian-ming Liu Yi-qian Wang Yi-sheng Gao Chaoqun Liu School of Mathematics and Statistics Jiangsu Normal UniversityXuzhou 221116China Department of Mathematics University of Texas at ArlingtonArlington 76019TexasUSA School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

In the new vortex identification method(Liu et al.2016)to represent the rotation level and capture and visualize the vortices,proposed in our previous study,the independence of the reference frame and the Galilean invariant were not *** the present study,the Galilean invariance of the omega vortex identification method is proved and several examples are presented to verify the conclusion.

关键词： vortex identification Ωmethod.Galilean invariance turbulence visualization