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The Boundary Element Method for Ordinary State-Based Peridynamics

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 2807-2834页

作者： Xue Liang Linjuan Wang State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering ScienceCollege of EngineeringPeking UniversityBeijing100871China capt-hedps and IFSA Collaborative Innovation Center of MoECollege of EngineeringPeking UniversityBeijing100871China School of Astronautics Beihang UniversityBeijing100191China

The peridynamics(PD),as a promising nonlocal continuum mechanics theory,shines in solving discontinuous *** to now,various numerical methods,such as the peridynamic mesh-free particlemethod(PD-MPM),peridynamic finite element method(PD-FEM),and peridynamic boundary element method(PD-BEM),have been ***-BEM,in particular,outperforms other methods by eliminating spurious boundary softening,efficiently handling infinite problems,and ensuring high computational ***,the existing PD-BEM is constructed exclusively for bond-based peridynamics(BBPD)with fixed Poisson’s ratio,limiting its applicability to crack propagation problems and scenarios involving infinite or semi-infinite *** this paper,we address these limitations by introducing the boundary element method(BEM)for ordinary state-based peridynamics(OSPD-BEM).Additionally,we present a crack propagationmodel embeddedwithin the framework ofOSPD-BEM to simulate crack *** validate the effectiveness of OSPD-BEM,we conduct four numerical examples:deformation under uniaxial loading,crack initiation in a double-notched specimen,wedge-splitting test,and threepoint bending *** results demonstrate the accuracy and efficiency of OSPD-BEM,highlighting its capability to successfully eliminate spurious boundary softening phenomena under varying Poisson’s ***,OSPDBEMsignificantly reduces computational time and exhibits greater consistencywith experimental results compared to PD-MPM.

关键词： Ordinary state-based peridynamics boundary element method crack propagation fracture toughness

Cylindrical effects in weakly nonlinear Rayleigh Taylor instability

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Chinese Physics B 2015年第1期24卷 388-393页

作者：刘万海马文芳王绪林 Research Center of Computational Physics Mianyang Normal University hedps and capt Peking University

The classical Rayleigh–Taylor instability（RTI） at the interface between two variable density fluids in the cylindrical geometry is explicitly investigated by the formal perturbation method up to the second order. Two styles of RTI, convergent（i.e., gravity pointing inward） and divergent（i.e., gravity pointing outwards） configurations, compared with RTI in Cartesian geometry, are taken into account. Our explicit results show that the interface function in the cylindrical geometry consists of two parts： oscillatory part similar to the result of the Cartesian geometry, and non-oscillatory one contributing nothing to the result of the Cartesian geometry. The velocity resulting only from the non-oscillatory term is followed with interest in this paper. It is found that both the convergent and the divergent configurations have the same zeroth-order velocity, whose magnitude increases with the Atwood number, while decreases with the initial radius of the interface or mode number. The occurrence of non-oscillation terms is an essential character of the RTI in the cylindrical geometry different from Cartesian one.

关键词： cylindrical effect Rayleigh–Taylor instability variable density fluid

Matching Boundary Conditions for a Heterogeneous Atomic Chain

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Chinese Physics Letters 2016年第8期33卷 1-4页

作者：陈星如刘舒瑜唐少强 hedps CAPT and LTCSDepartment of Mechanics and Engineering ScienceCollege of EngineeringPeking University

We propose accurate boundary treatments for a heterogeneous atomic chain, in terms of matching boundary conditions （MBCs）. The main challenge lies in reproducing the physical reflection across the boundary to a correct amount. With reflection coefficients we demonstrate that the accuracy is improved when more atoms are used under the boundary condition. The inclusion of an atom in the embedded sublattice B may considerably enhance the performance. Numerical testing illustrates the effectiveness of the proposed MBCs.

关键词： for on it Matching Boundary Conditions for a Heterogeneous Atomic Chain of is MBC that

Tunable energy spectrum betatron x-ray sources in a plasma wakefield

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Chinese Physics B 2024年第8期33卷 344-350页

作者：奚传易寿寅任韩立琦阿卜杜伍普尔·阿布力米提刘晓丹赵研英余金清 Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications School of Physics and ElectronicsHunan UniversityChangsha 410082China Center for Relativistic Laser Science Institute for Basic ScienceGwangjuKorea State Key Laboratory of Nuclear Physics and Technology and Key Laboratory of HEDP of the Ministry of EducationCAPTPeking UniversityBeijing 100871China

X-ray sources with tunable energy spectra have a wide range of applications in different scenarios due to their different penetration ***,existing x-ray sources face difficulties in terms of energy *** this paper,we present a scheme for tuning the energy spectrum of a betatron x-ray generated from a relativistic electron bunch oscillating in a plasma *** center energy of the x-ray source can be tuned from several keV to several hundred keV by changing the plasma density,thereby extending the control range by an order of *** different central energies,the brightness of the betatron radiation is in the range of 3.7×10^(22)to 5.5×10^(22)photons/(0.1%BW·s·mm^(2)·mrad^(2))and the photon divergence angle is about 2 *** high-brightness,energy-controlled betatron source could pave the way to a wide range of applications requiring photons of specific energy,such as phase-contrast imaging in medicine,non-destructive testing and material analysis in industry,and imaging in nuclear physics.

关键词： betatron plasma physics x-ray plasma wakefield acceleration(PWFA)

Human radiological safety assessment for petawatt laser-driven ion acceleration experiments in CLAPA-T

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Matter and Radiation at Extremes 2024年第4期9卷 8-15页

作者： Xiaopeng Zhang Jiarui Zhao Shengxuan Xu Xun Chen Ying Gao Shiyou Chen Kun Zhu Xueqing Yan Wenjun Ma State Key Laboratory of Nuclear Physics and Technology and Key Laboratory of HEDP of the Ministry of EducationCAPTPeking UniversityBeijing 100871China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsCASBeijing 100049China Beijing Laser Acceleration Innovation Center HuairouBeijing 101400China Institute of Guangdong Laser Plasma Technology BaiyunGuangzhou 510540China

The newly built Compact Laser Plasma Accelerator-Therapy facility at Peking University will deliver 60 J/1 Hz laser pulses with 30 fs *** by this petawatt laser facility,proton beams with energy up to 200 MeV are expected to be generated for tumor *** high-repetition operation,both prompt radiation and residual radiation may cause safety ***,human radiological safety assessment before commissioning is *** this paper,we simulate both prompt and residual radiation using the Geant4 and FLUKA Monte Carlo codes with reasonable proton and as-produced electron beam *** find that the prompt radiation can be shielded well by the concrete wall of the experimental hall,but the risk from residual radiation is nonnegligible and necessitates adequate radiation *** the basis of the simulation results,we discuss the constraints imposed by radiation safety considerations on the annual working time,and we propose radiation cooling strategies for different shooting modes.

关键词： laser prompt acceleration

Dripping retardation with corrugated ceiling

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Applied Mathematics and Mechanics(English Edition) 2018年第8期39卷 1165-1172页

作者： Dong LUO Jianjun TAO capt-hedps SKLTCS Collaborative Innovation Center of IFSADepartment of Mechanics and Engineering Science College of EngineeringPeking University

The instabilities of a pendent viscous thin film underneath two corrugated ceilings are studied numerically and theoretically in comparison with the case of a flat wall. With the same initial interface perturbations, it is shown numerically that both the supercritical instability and the subcritical instability can be retarded by the in-phase corrugated ceilings. The lubrication approximation is used to explain the retardation effect of the corrugated ceiling on the supercritical instability of the pendant film, where the linear growth rate is revealed to be power three of the initial film thickness.

关键词： pendent film surface tension Rayleigh-Taylor instability(RTI) corrugated wall

Stability of Atomic Simulations with Matching Boundary Conditions

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Advances in Applied Mathematics and Mechanics 2014年第5期6卷 539-551页

作者： Shaoqiang Tan Songsong Ji hedps CAPT and LTCSCollege of EngineeringPeking UniversityBeijing 100871China

.We explore the stability of matching boundary conditions in one space dimension,which were proposed recently for atomic simulations(Wang and Tang,***.,93(2013),pp.1255–1285).For a finite segment of the linear harmonic chain,we construct explicit energy functionals that decay along with *** a nonlinear atomic chain with its nonlinearity vanished around the boundaries,an energy functional is constructed for the first order matching boundary *** verifications are also presented.

关键词： Stability matching boundary condition atomic simulation

Magneto-Rayleigh-Taylor instability in compressible Z-pinch liner plasmas

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Chinese Physics B 2017年第7期26卷 244-249页

作者：杨学肖德龙丁宁刘杰 Institute of Applied Physics and Computational Mathematics Graduate School China Academy of Engineering Physics hedps capt and CICIFSA MoE Peking University

In this paper, the characteristics of magneto-Rayleigh-Taylor（MRT） instability of liner plasmas in Mag LIF is theoretically investigated. A three-region slab model, based on ideal MHD equations, is used to derive the dispersion relation of MRT instability. The effect of compressibility on the development of MRT instability is specially examined. It is shown that the growth rate of MRT instability in compressible condition is generally lower than that in incompressible condition in the presence of magnetic field. In the case of zero magnetic field, the growth rate in compressible assumption is approximately the same as that in incompressible assumption. Generally, MRT instability in（x, y） plane can be remarkably mitigated due to the presence of magnetic field especially for short-wavelength perturbations. Perturbations may be nearly completely mitigated when the magnetic field is increased to over 1000 T during liner implosions. The feedthrough of MRT instability in liner outer surface on inner surface is also discussed.

关键词： magneto-Rayleigh-Taylor(MRT) instability magnetized liner inertial fusion(Mag LIF) Z-pinch compressibility

Artificial boundary conditions for Euler–Bernoulli beam equation

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Acta Mechanica Sinica 2014年第5期30卷 687-692页

作者： Shao-Qiang Tang Eduard G.Karpov hedps CAPT and LTCS College of EngineeringPeking University Department of Civil and Materials Engineering University of Illinois at ChicagoChicago IL60607 USA

In a semi-discretized Euler-Bernoulli beam equa- tion, the non-nearest neighboring interaction and large span of temporal scales for wave propagations pose challenges to the effectiveness and stability for artificial boundary treat- ments. With the discrete equation regarded as an atomic lattice with a three-atom potential, two accurate artificial boundary conditions are first derived here. Reflection co- efficient and numerical tests illustrate the capability of the proposed methods. In particular, the time history treatment gives an exact boundary condition, yet with sensitivity to nu- merical implementations. The ALEX （almost EXact） bound- ary condition is numerically more effective.

关键词： Euler-Bernoulli beam. Artificial boundary con- dition - Wave propagation