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Combination of direct-forcing fictitious domain method and sharp interface method for dielectrophoresis of particles

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Particuology 2010年第4期8卷 351-359页

作者： Yang Shi Zhaosheng Yu xueming shao State Key Laboratory of Fluid Power Transmission and Control Department of Mechanics. Zhejiang University Hangzhou 310027 China

In this paper, we combine the direct-forcing fictitious domain （DF/FD） method and the sharp interface method to resolve the problem of particle dielectrophoresis in two dimensions. The flow field and the motion of particles are solved with the DF/FD method, the electric field is solved with the sharp inter- face method, and the electrostatic force on the particles is computed using the Maxwell stress tensor method. The proposed method is validated via three problems： effective conductivity of particle compos- ite between two planar plates, cell trapping in a channel, and motion of particles due to both conventional and traveling wave dielectrophoretic forces.

关键词： Direct-forcing fictitious domain method Sharp interface methodMaxwell stress tensor method Dielectrophoresis Direct numerical simulation Cell trapping

Time-optimal guidance for intercepting moving targets with impact-angle constraints

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Chinese Journal of Aeronautics 2022年第7期35卷 157-167页

作者： Yuan ZHENG Zheng CHEN xueming shao Wenjie ZHAO School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310027China

The minimum-time path for intercepting a moving target with a prescribed impact angle is studied in the *** candidate paths from Pontryagin’s maximum principle are synthesized,so that each candidate is related to a zero of a real-valued *** is found that the real-valued functions or their first-order derivatives can be converted to polynomials of at most fourth *** a result,each candidate path can be computed within a constant time by embedding a standard polynomial solver into the typical bisection *** control strategy along the shortest candidate eventually gives rise to the time-optimal guidance ***,the developments of the paper are illustrated and verified by three numerical examples.

关键词： Dubins vehicle Guidance law Minimum-time path Optimal guidance Path planning

Mechanism analysis of hysteretic aerodynamic characteristics on variable-sweep wings

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Chinese Journal of Aeronautics 2023年第5期36卷 212-222页

作者： Lifang ZENG Liu LIU xueming shao Jun LI Zhejiang University Hangzhou 310027China Rotor Aerodynamics Key Laboratory China Aerodynamics Research and Development CenterMianyang 621000China

Variable-sweep wings have large shape-changing capabilities and wide flight envelops,which are considered as one of the most promising directions for intelligent morphing *** investigations always focus on several static states in the varying sweep process,which ignore the unsteady aerodynamic ***,deviations to static aerodynamic forces are inevitably caused by dynamic sweep *** this work,first,unsteady aerodynamic characteristics on a typical variable-sweep UAV with large aspect ratio were ***,deep mechanism of unsteady aerodynamic characteristics in the varying sweep process was ***,numerical simulation method integrated with structured moving overset grids was applied to solve the unsteady fluid of varying sweep *** simulation results of a sweep forward-backward circle show a distinct dynamic hysteresis loop surrounding the static data for the aerodynamic *** with the static lift coefficients,at the same sweep angles,dynamic lift coefficient in sweep forward process are all smaller,while dynamic sweep backward lift coefficient are all *** addition,dynamic deviations to static lift coefficient are positively related with the varying sweep *** study on the unsteady aerodynamic characteristics indicates that three key factors lead to the dynamic hysteresis loop in varying sweep *** are the effects of additional velocity caused by varying sweep motion,the effects of flow hysteresis and *** additional velocity induced by sweep motion affects the transversal flow direction along the wing and the effective angle of attack at the airfoil *** physical properties of flow,the hysteresis and viscosity affect the unsteady aerodynamic characteristics by flow separation and induced vortexes.

关键词： Hysteresis Mechanism Numerical simulation Unsteady aerodynamic characteristics Variable-sweep wings

NUMERICAL FLOW VISUALIZATION OF A MIXING LAYER

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Journal of Hydrodynamics 1998年第4期10卷 45-53页

作者： Lin, Jianzhong Yu, Zhaosheng shao, xueming Zhejiang Univ Hangzhou China

Kelvin-Helmhotz roll up of the 3-D time-developing mixing was simulated numerically. The dye lines or fluid interfaces were presented by computing a passive scalar at high Peclet number. The hydric bubbles were also simulated numerically. To help understanding the visualization results, the behaviour of coherent structures were analyzed. A comparison between vortical structure and passive scalar contours indicates that the wrapping by the vortices largely dominates the evolution of passive scalar.

关键词： Bubbles (in fluids) Computer applications Flow of water Hydrodynamics Laminar flow Turbulent flow

Effects of finite-size neutrally buoyant particles on the turbulent channel flow at a Reynolds number of 395

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Applied Mathematics and Mechanics(English Edition) 2019年第2期40卷 293-304页

作者： Zhaosheng YU Chenlin ZHU Yu WANG xueming shao State Key Laboratory of Fluid Power and Mechatronic System Department of MechanicsZhejiang University

A direct-forcing fictitious domain(DFFD) method is used to perform fully resolved numerical simulations of turbulent channel flows laden with large neutrally buoyant particles. The effects of the particles on the turbulence(including the mean velocity,the root mean square(RMS) of the velocity fluctuation, the probability density function(PDF) of the velocity, and the vortex structures) at a friction Reynolds number of 395 are investigated. The results show that the drag-reduction effect caused by finite-size spherical particles at low particle volumes is negligibly small. The particle effects on the RMS velocities at Re_τ = 395 are significantly smaller than those at Re_τ = 180, despite qualitatively the same effects, i.e., the presence of particles decreases the maximum streamwise RMS velocity near the wall via weakening the large-scale streamwise vortices,and increases the transverse and spanwise RMS velocities in the vicinity of the wall by inducing smaller-scale vortices. The effects of the particles on the PDFs of the fluid fluctuating velocities normalized with the RMS velocities are small, regardless of the particle size, the particle volume fraction, and the Reynolds number.

关键词： turbulent channel flow finite-size particle direct numerical simulation(DNS)

Numerical investigation of the effects of large particles on turbulent channel flow

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Numerical investigation of the effects of large particles on...

Nonlinear optimal transient growth in the wake of a transversely oscillating cylinder

23rd International Congress of Theoretical and Applied Mechanics

作者： xueming shao Tenghu Wu Zhaosheng Yu State Key Laboratory of Fluid Power Transmission and Control Department of MechanicsZhejiang University

＜正＞A fictitious domain method is used to perform fully resolved direct numerical simulations of particle-laden turbulent flow in a horizontal *** effects of large neutrally buoyant particles on the turbulence statistics and structures are investigated for different volume fractions and particle sizes at the channel

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Nonlinear optimal transient growth in the wake of a transver...

Dynamic Simulation of Shear-induced Particle Migration in a Two-dimensional Circular Couette Device

第十届全国流体力学学术会议

作者： Liping Sun Xuerui Mao Jian Deng xueming shao Department of Mechanics Zhejiang University Department of Mechanical Materials and Manufacturing EngineeringThe University of Nottingham

We study numerically the two-and three-dimensional incompressible flow in the wake of a circular cylinder forced to oscillate transversely at Re = *** oscillation amplitude and frequency are fixed at A = 0.1 and f = fU/D = 0.2 *** note that this frequency is very close to the natural shedding frequency for the flow around a static cylinder at the same Reynolds ***,we perform nonlinear optimal transient growth analysis,which takes the two-dimensional result as the base flow and solve the three-dimensional nonlinear perturbation *** results show that the growth of the optimal perturbation is linear at small magnitude of initial perturbation,or perturbation energy,with the perturbation vorticity concentrates around the ***,at large magnitude of initial perturbation,the growth of the optimal perturbation is nonlinear,with the vorticity in the upstream of the lower surface observed to spread downstream of the *** also carry out three-dimensional direct simulations with the flow field initialized by a superposition of the base flow and a linearly optimal *** small magnitude,the perturbation is predominantly monochromatic in the span and always exists in *** dominant modes are even,showing that the wake is a superposition of mode 0,2 and *** mode 0 represents the spanwise mean *** large magnitude,the positive and negative streamwise velocity perturbations are coupled and the positive perturbations cover a large area than the negative *** this situation,the wake is a superposition of mode 0,2 and *** the evolution of nonlinearity,mode 1 gradually overtakes mode 2.

关键词： Nonlinear optimal transient growth Wake instability Oscillating cylinder

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Chinese Journal of Chemical Engineering 2007年第3期15卷 333-338页

作者：余钊圣邵雪明 Roger Tanner Department of Nlechanics State Key Laboratory of Fluid Pow~ Transmis~on and Control Zhejiang UniversityHangzhou 310027 China School of Aerospace Mechanical and Mechatronic Engineering University of Sydney NSW 2006 Australia

The shear-induced migration of neutrally-buoyant non-colloidal circular particles in a two-dimensional circular Couette flow is investigated numerically with a distributed Lagrange multiplier based fictitious domain *** effects of inertia and volume fraction on the particle migration are *** results indicate that inertia has a negative effect on the particle *** consistence with the experimental observations,the rapid migration of particles near the inner cylinder at the early stage is observed in the simulation,which is believed to be related to the chain-like clustering of *** migration of circular particles in a plane Poiseuille flow is also examined in order to further confirm the effect of such clustering on the particle migration at early *** is tendency for the particles in the vicinity of outer cylinder in the Couette device to pack into concentric rings at late stage in case of high particle concentration.

关键词： shear-induced particle migration dynamic simulation circular Couette flow clustering

Spontaneous Recovery in Directed Dynamical Networks

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Engineering 2024年第6期37卷 208-214页

作者： xueming Liu Xian Yan H.Eugene Stanley School of Artificial Intelligence and Automation&The MOE Engineering Research Center of Autonomous Intelligent Unmanned Systems&the Key Laboratory of Image Processing Huazhong University of Science and TechnologyWuhan 430074China Center for Polymer Studies Department of PhysicsBoston UniversityBostonMA 02215USA

Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneously return to normal after a seizure,and traffic flow can become smooth again after a *** studies on the spontaneous recovery of dynamical networks have been limited to undirected ***,most real-world networks are *** fill this gap,we build a model in which nodes may alternately fail and recover,and we develop a theoretical tool to analyze the recovery properties of directed dynamical *** find that the tool can accurately predict the final fraction of active nodes,and the prediction accuracy decreases as the fraction of bidirectional links in the network increases,which emphasizes the importance of directionality in network *** to different initial states,directed dynamical networks may show alternative stable states under the same control parameter,exhibiting hysteresis *** addition,for networks with finite sizes,the fraction of active nodes may jump back and forth between high and low states,mimicking repetitive failure-recovery *** findings could help clarify the system recovery mechanism and enable better design of networked systems with high resilience.

关键词： Network resilience Directed dynamical networks Spontaneous recovery