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The Anti-Plane Problem of Collinear Interface Cracks Emanating From a Circular Hole in 1D Hexagonal Quasicrystal Bi-Materials
ZHANG Bingcai, DING Shenghu, ZHANG Laiping
 doi: 10.21656/1000-0887.420202
Abstract(33) HTML(15) PDF(3)
The anti-plane problem of asymmetric collinear interface cracks emanating from a circular hole in 1D hexagonal quasicrystal bi-materials was studied. With the Stroh formula and the complex function method, the complex potential functions under the coupling action of the phonon field and the phason field were obtained. The analytical expressions of the stress intensity factor (SIF) and the energy release rate (ERR) at the crack tip were given. The effects of the circular hole radius and the crack length on the SIF, and the effects of the coupling coefficient, the phonon field stress and the phason field stress on the ERR, were discussed. The results show that, the SIF tends to be stable with the increase of the right crack length for a constant circular hole radius. For a certain phason field stress value, the ERR reaches the minimum value, which indicates that a specific phason field stress can inhibit the crack growth.
Sampling Consensus of Second-Order Multi-Agent Systems Based on Time-Varying Topology
ZHENG Liying, YANG Yongqing, XU Xianyun
 doi: 10.21656/1000-0887.420220
Abstract(9) HTML(12) PDF(1)
The sampling consensus of second-order multi-agent systems with time-varying topology is investigated based on the constant position difference and consistent speed. Firstly, the virtual leader is introduced and the sampling consensus problem of multi-agent systems is transformed into the stability problem of the corresponding error system. Secondly, by estimating the sampling error, the influence of sampling error on system consistency is studied. Finally, by virtue of the Lyapunov stability theory, the stability of the constructed error system is analyzed, and a sufficient condition for the stability of the error system is given. The numerical simulation results verify the effectiveness and correctness of the theoretical analysis.
Mesoscopic Numerical Study on Flow Boiling Heat Transfer Performance in Channels With Multiple Rectangular Heaters
LI Yingxue, WANG Haoyuan, LOU Qin
 doi: 10.21656/1000-0887.420325
Abstract(6) HTML(13) PDF(1)
The flow boiling phenomenon in a channel with multiple rectangular heaters under constant wall temperature was numerically studied by lattice Boltzmann method. The effects of distance between/among heater, heater length and heater surface wettability on bubble morphology, bubble area and heat flux of the heater surface were studied. The results show that the bubble growth rate increases with the increase of the distance between/among heaters, the larger bubble area promotes the nucleated bubbles to leave the heater surface in advance, and the corresponding boiling heat transfer performance increases by 12% with the increase of the distance between/among heaters from 250 lattices to 1000 lattices. On the other hand, the longer the heater length, the earlier the bubble nucleation time and separation time from the heater surface, and the better the boiling heat transfer performance, and the boiling heat transfer performance increases by 13% with the increase of the heater length from 16 lattices to 22 lattices. In addition, the bubble nucleation time of the hydrophilic surface is later than that of the hydrophobic surface. Compared with the hydrophilic surface, there are residual bubbles on the hydrophobic surface after the bubbles leave the heater. The average heat flux and bubble area of hydrophilic surface are less than those of hydrophobic surface. When the contact Angle changes from 77° to 120°, the heat transfer performance increases by 26%. Finally, through the orthogonal test scheme, it is found that the wettability of the heat exchanger surface has the greatest influence on the flow boiling heat transfer performance, while the heater length has the least influence on the flow boiling heat transfer performance.
Research on the Deposition and Orientation Characteristics of Cylindrical Particles in a Gas-solid Two-phase Turbulent Flow Through a Curved Tube
LI Liang, SHI Ruifang, LIN Jianzhong
 doi: 10.21656/1000-0887.420320
Abstract(37) HTML(24) PDF(3)
In the case of Reynolds number Re=3000 ~ 50000, Stokes number St=0.1 ~ 10, Dean number De=1400 ~ 2800, the orientation and deposition characteristics of cylindrical particles with aspect ratio β=2 ~ 12 in a turbulent flow through a curved tube are studied. The motion of cylindrical particles is described by the slender body theory combined with the Newton's second law. The orientation distribution function of cylindrical particles is given by the Fokker Planck equation. The mean velocity of the flow is obtained by solving the Reynolds-averaged Navier-Stokes equation and Reynolds stress equation. The turbulent fluctuating velocity acting on particles is described by the kinetic simulation sweeping model. By solving the equations of turbulent flow and particle motion and orientation distribution function, the orientation distribution of particles on the cross-section at different axial positions and outlet is obtained and analyzed. The effects of various parameters on the deposition rate of particles are discussed. The results showed that the main axis of particles tends to the flow direction with the increase of St and β, and the decrease of De and Re. Deposition rate of particles increases with increasing De, Re and β. However, it shows a non monotonic trend with the change of St. Conclusion has reference value for practical engineering application.
Size-Dependent Effect of Micro-Nano Mindlin Plate Based on Couple Stress Theory
Jianghong XUE, Zanhang HE, Fei XIA, Zerong LI, Fusong JIN, Peng YANG
 doi: 10.21656/1000-0887.420171
Abstract(18) HTML(14) PDF(0)
A Mindlin plate theory for micro-nano structures is proposed based on couple stress theory. A length scale parameter was introduced to take into account the scale effect and the constitutive equations of the micro-nano Mindlin plate were derived by considering the transverse shear deformation. The governing equations in terms of displacements and the slope functions of buckling and free vibration for shear deformation micro-nano plate were further deduced from force equilibrium conditions. The analytical solutions of buckling and free vibration for shear deformation micro-nano plate were obtained by separating the displacement and rotation variables in space and time domains. Two scenarios of boundary conditions were analyzed: SSSS (simply supported by four edges) and SCSC (two opposite edges simply supported and other two edges clamped). A MATLAB program was developed to compute the critical buckling and natural frequency with different value of scale ratio, aspect ratio and length-to-thickness ratio. The theoretical solutions are compared with the results from ABAQUS finite element analysis and the predictions obtained from existing studies and found in good agreement with the other two methods. The results show that the scale effect has a significant effect on the buckling load and the natural frequency.
Analysis and Simulation of Natural Frequencies of a Slightly Curved Pipe
Jiarui YUAN, Hu DING, Liqun CHEN
 doi: 10.21656/1000-0887.420299
Abstract(32) HTML(18) PDF(9)
For the transverse vibration of slightly curved pipe, a dynamic mechanical model based on Timoshenko beam theory is established for the first time. The natural vibration characteristic of slightly curved pipe under the influence of the fluid flow is analyzed. With generalized Hamiltonian principle, the governing equation of the transverse vibration of slightly curved pipe considering the effect of fluid-structure coupling is derived. Based on Galerkin truncation, the natural frequencies of slightly curved pipe are obtained by generalized eigenvalue method. Effects of the fluid velocity and the initial deflection on the natural vibration characteristic of the pipe are studied. The equivalent stiffness and equivalent damping method base on finite element simulation for the natural vibration of the slightly curved pipe are developed. Then through the finite element numerical simulation software, the results of Galerkin truncation method and the effectiveness of the Timoshenko model are verified. The results show that fluid velocity and the initial bending degree both have significant effects on the natural frequencies of slightly curved pipe.
An Improved Third Order WENO Scheme Based on a New Reference Smoothness Indicator
Yahui WANG
 doi: 10.21656/1000-0887.420194
Abstract(52) HTML(12) PDF(6