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Targets capture by distributed active swarms via bio-inspired reinforcement learning

Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 210-221页

作者： Kun Xu Yue Li Jun Sun Shuyuan Du Xinpeng Di Yuguang Yang Bo Li Institute of Biomechanics and Medical engineering Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua University Institute of Nuclear and New Energy Technology Tsinghua University Shanghai Aerospace Control Technology Institute Shanghai key laboratory of Aerospace Intelligent Control Technology College of Automation engineering Nanjing University of Aeronautics and Astronautics

Natural swarms arranged from cells to herds are usually decentralized but display intriguing collective intelligence in coordinating individuals across large scales to efficiently achieve their common goals. Learning from nature may provide new strategies for controlling collective dynamics of synthetic swarms to accomplish specific functions. Here, we present a bioinspired computational framework that steers distributed active swarms to collectively capture and merge targets via reinforcement learning. We exploit collective milling structures of natural herds to cage the targets, and adopt a switching control policy inspired by sperms' chiral dynamics to optimize the trajectories of individuals, through which the active swarms can selforganize to enclose single or multiple distant targets in a dynamical, adaptive and scalable manner. There exists a critical swarm size, beyond which the excessive competition between agents would generate large mechanical forces, leading to capture instability but enabling the transition from short-distance to long-distance merging capture of multiple targets. This work provides physical insights into distributed active swarms and could offer a multilevel, decentralized strategy toward controlling swarm robotics in wide applications such as bio-medical devices, machine immunity, and target clearance.

关键词： swarm intelligence robotics multi-tasks artificial intelligence bionics

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Vector meson's spin alignments in high energy reactions

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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 5-20页

作者： Jin-Hui Chen Zuo-Tang Liang Yu-Gang Ma Xin-Li Sheng Qun Wang key laboratory of Nuclear Physics and Ion-beam Application (MoE) Institute of Modern PhysicsFudan University Institute of Frontier and Interdisciplinary Science Key Laboratory of Particle Physics and Particle Irradiation (MOE)Shandong University INFN-Firenze department of modern Physics University of Science and Technology of China School of mechanics and Physics Anhui University of Science and Technology

The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National laboratory （BNL）.It provides a unique opportunity to probe the correlation between the polarized quark and antiquark in the strongly coupled quark-gluon plasma （sQGP） produced in relativistic heavy ion collisions,opening a new window to explore the properties of s *** addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e+e-annihilations at high energies where hadron production is dominated by quark fragmentation *** results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization *** comprehensive studies in different hadronization processes are *** this article,we present a brief review of theoretical and experimental advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.

关键词： vector meson spin alignment global polarization relativistic heavy ion collisions fragmentation

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Critical transition Reynolds number for plane channel flow

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Applied Mathematics and mechanics(English Edition) 2017年第10期38卷 1415-1424页

作者： Yongming ZHANG department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics

The determination of the critical transition Reynolds number is of practical importance for some engineering problems. However, it is not available with the current theoretical method, and has to rely on experiments. For supersonic/hypersonic boundary layer flows, the experimental method for determination is not feasible either. Therefore, in this paper, a numerical method for the determination of the critical transition Reynolds number for an incompressible plane channel flow is proposed. It is basically aimed to test the feasibility of the method. The proposed method is extended to determine the critical Reynolds number of the supersonic/hypersonic boundary layer flow in the subsequent papers.

关键词： critical transition Reynolds number plane channel flow boundary layerflow

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Application of Arnoldi method to boundary layer instability

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Chinese Physics B 2015年第12期24卷 379-391页

作者：张永明罗纪生 department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics

The Arnoldi method is applied to boundary layer instability, and a finite difference method is employed to avoid the limit of the finite element method. This modus operandi is verified by three comparison cases, i.e., comparison with linear stability theory（LST） for two-dimensional（2D） disturbance on one-dimensional（1D） basic flow, comparison with LST for three-dimensional（3D） disturbance on 1D basic flow, and comparison with Floquet theory for 3D disturbance on 2D basic flow. Then it is applied to secondary instability analysis on the streaky boundary layer under spanwise-localized free-stream turbulence（FST）. Three unstable modes are found, i.e., an inner mode at a high-speed center streak, a sinuous type outer mode at a low-speed center streak, and a sinuous type outer mode at low-speed side streaks. All these modes are much more unstable than Tollmien–Schlichting（TS） waves, implying the dominant contribution of secondary instability in bypass transition. The modes at strong center streak are more unstable than those at weak side streaks, so the center streak is ‘dangerous＇ in secondary instability.

关键词： Arnildi method linear stability theory Floquet theory secondary instability

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Near-wall behaviors of oblique-shock-wave/turbulent-boundary-layer interactions

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Applied Mathematics and mechanics(English Edition) 2017年第10期38卷 1357-1376页

作者： Mingsheng YE Ming DONG department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics

A direct numerical simulation （DNS） on an oblique shock wave with an incident angle of 33.2° impinging on a Mach 2.25 supersonic turbulent boundary layer is performed. The numerical results are confirmed to be of high accuracy by comparison with the reference data. Particular efforts have been made on the investigation of the near-wall behaviors in the interaction region, where the pressure gradient is so significant that a certain separation zone emerges. It is found that, the traditional linear and loga- rithmic laws, which describe the mean-velocity profiles in the viscous and meso sublayers, respectively, cease to be valid in the neighborhood of the interaction region, and two new laws of the wall are proposed by elevating the pressure gradient to the leading order. The new laws are inspired by the analysis on the incompressible separation flows, while the compressibility is additionally taken into account. It is verified by the DNS results that the new laws are adequate to reproduce the mean-velocity profiles both inside and outside the interaction region. Moreover, the normalization adopted in the new laws is able to regularize the Reynolds stress into an almost universal distribution even with a salient adverse pressure gradient （APG）.

关键词： shock wave turbulent boundary layer direct numerical simulation (DNS),adverse pressure gradient (APG) separation

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Revealing and predicting the long-term biomechanical response of orthokeratology by developing a patient-specific computational model

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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 156-168页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi Zhanli Liu Kaijie Wang department of engineering mechanics School of Aerospace Engineering Tsinghua University Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Sciences Key Lab

Orthokeratology(OK) is widely used for effective myopia correction and control. However, the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment, complicating accurate predictions of treatment outcomes. In this paper, we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal thickness. Clinical experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 months. Based on the experimental data, a patient-specific computational biomechanical model for OK was established and validated. Specifically, the anisotropic mechanical properties of the cornea were incorporated into the model to describe the significant difference between its shear modulus(29.5 kPa) and tensile modulus(768.4 kPa). Additionally, a viscohyperelastic material model with a prolonged corneal relaxation time of 5.6 h was developed to capture the long-term deformation response. The results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea's low shear resistance. Modeling the extended corneal relaxation time is crucial for predicting long-term biomechanical responses. The computational model effectively captures long-term changes in central corneal thickness, potentially improving OK lens fitting accuracy.

关键词： orthokeratology computational biomechanical model long-term viscoelasticity myopia correction

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Self-consistent parabolized stability equation(PSE) method for compressible boundary layer

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Applied Mathematics and mechanics(English Edition) 2015年第7期36卷 835-846页

作者： Yongming ZHANG Caihong SU department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics Tianjin University

The parabolized stability equation （PSE） method has been proven to be a useful and convenient tool for the investigation of the stability and transition problems of boundary layers. However, in its original formulation, for nonlinear problems, the complex wave number of each Fourier mode is determined by the so-called phase-locked rule, which results in non-self-consistency in the wave numbers. In this paper, a modification is proposed to make it self-consistent. The main idea is that, instead of allowing wave numbers to be complex, all wave numbers are kept real, and the growth or decay of each mode is simply manifested in the growth or decay of the modulus of its shape function. The validity of the new formulation is illustrated by comparing the results with those from the corresponding direct numerical simulation （DNS） as applied to a problem of compressible boundary layer with Mach number 6.

关键词： parabolized stability equation (PSE) boundary layer direct numericalsimulation (DNS) self-consistent

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A simulation on bypass transition and its key mechanism

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Science China(Physics,mechanics & Astronomy) 2013年第4期56卷 775-784页

作者： DONG Ming ZHOU Heng department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics

The scenario of bypass transition is generally described theoretically as follows: low-frequency disturbances in the free-stream would generate long stream-wise streaks in the boundary layer, which later would induce secondary instability, leading to rapid increase of high-frequency disturbances, then possibly turbulent spots would emerge, and through their merging, fully developed turbulence appears. This description, however, is insufficient in the sense that it does not provide the explanation on why during the breakdown stage, a large number of waves with different frequencies and wave numbers would appear almost simultaneously, leading to a swift change of the mean flow profile. In this paper, the mechanism leading to this phenomenon is found to be the change of the stability characteristics of mean flow profile, which has a positive feedback effect on the change of the profile itself. And another interesting finding is that, during the transition, the unstable disturbance waves which appear first belong to a branch of inviscid modes, while following the change of the stability characteristics of the mean flow profile, the disturbance waves will change to another branch of inviscid modes, and the latter play the key role in bypass transition.

关键词： bypass transition breakdown instability streak inviscid

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Physical implication of two problems in transition prediction of boundary layers based on linear stability theory

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Science China(Physics,mechanics & Astronomy) 2014年第5期57卷 950-962页

作者： SU CaiHong department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics

Up to now,the most widely used method for transition prediction is the one based on linear stability *** it is applied to three-dimensional boundary layers,one has to choose the direction,or path,along which the growth rate of the disturbance is to be *** direction given by using saddle point method in the theory of complex variable function is seen as mathematically most ***,unlike the saddle point method applied to water waves,here its physical meaning is not so obvious,as the frequency and wave number may be *** on some occasions,in advancing the integration of the growth rate of the disturbance,up to a certain location,one may not be able to continue the integration,because the condition for specifying the direction set by the saddle point method can no longer be satisfied on the basis of continuously varying wave *** this paper,these two problems are discussed,and suggestions for how to do transition prediction under the latter condition are provided.

关键词： boundary layer transition prediction linear stability theory DNS

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Experimental study on spectrum and multi-scale nature of wall pressure and velocity in turbulent boundary layer

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Chinese Physics B 2015年第6期24卷 385-394页

作者：郑小波姜楠 department of mechanics Tianjin University tianjin key laboratory of modern engineering mechanics The State key laboratory of Nonlinear mechanics Institute of MechanicsChinese Academy of Sciences

When using a miniature single sensor boundary layer probe, the time sequences of the stream-wise velocity in the turbulent boundary layer （TBL） are measured by using a hot wire anemometer. Beneath the fully developed TBL, the wall pressure fluctuations are attained by a microphone mechanism with high spatial resolution. Analysis on the statistic and spectrum properties of velocity and wall pressure reveals the relationship between the wall pressure fluctuation and the energy-containing structure in the buffer layer of the TBL. Wavelet transform shows the multi-scale natures of coherent structures contained in both signals of velocity and pressure. The most intermittent wall pressure scale is associated with the coherent structure in the buffer layer. Meanwhile the most energetic scale of velocity fluctuation at y＋ = 14 provides a specific frequency f9 ≈ 147 Hz for wall actuating control with Ret = 996.

关键词： multi-scale coherent structures hot wire anemometry microphone wavelet transform

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