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管状上皮组织的三维形态发生

Acta Mechanica Sinica 2024年第2期40卷 237-243页

作者：于鹏宇李博 institute of Biomechanics and Medical engineering Applied Mechanics LaboratoryDepartment of Engineering MechanicsTsinghua UniversityBeijing100084China

管状上皮组织是组成多种器官的基本结构,其形态发生涉及到细胞变形、生化信号转导,以及细胞之间和细胞与细胞外基质之间的相互作用.目前尚未完全清楚力学和生化信号之间的相互作用如何调节该形态学过程.本文构建了耦合生化信号通路的三... 详细信息

管状上皮组织是组成多种器官的基本结构,其形态发生涉及到细胞变形、生化信号转导,以及细胞之间和细胞与细胞外基质之间的相互作用.目前尚未完全清楚力学和生化信号之间的相互作用如何调节该形态学过程.本文构建了耦合生化信号通路的三维细胞顶点模型,用于探究管状组织的形态发生.数值计算结果表明管腔尺寸受到细胞和细胞外基质的力学性质的影响,且细胞的力学-化学耦合的变形可以激发斑点状和条带状的超细胞肌动球蛋白斑图,进而介导组织形成波浪形和竹节形的管腔结构,该过程会受到化学扩散强度的调节.本研究突显了力学-化学相互作用在生物组织形态动力学中的重要作用,并且提供了一个三维计算框架以深入理解生命系统中复杂的斑图形成过程.

关键词：化学相互作用细胞变形肌动球蛋白形态发生管状组织细胞外基质三维形态波浪形

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辐射加热颗粒槽道湍流两相流的相间传热特性

Acta Mechanica Sinica 2024年第2期40卷 54-64页

作者：唐晓峰潘明杨文武董宇红 Shanghai institute of Applied Mathematics and mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai200072China Shanghai Key Laboratory of mechanics in Energy engineering and Shanghai institute of Aircraft mechanics and Control Shanghai200072China

本文采用直接数值模拟方法结合拉格朗日点-粒模型研究了携带辐射热惯性颗粒的竖直槽道湍流两相流相间传热特性.研究中采用双向耦合模型描述分散相颗粒与流体之间的动量交换和热交换,辐射强度和颗粒Stokes数范围分别为1≤q/q0≤20,0.36×... 详细信息

本文采用直接数值模拟方法结合拉格朗日点-粒模型研究了携带辐射热惯性颗粒的竖直槽道湍流两相流相间传热特性.研究中采用双向耦合模型描述分散相颗粒与流体之间的动量交换和热交换,辐射强度和颗粒Stokes数范围分别为1≤q/q0≤20,0.36×10^(−1)≤Stf≤2.16×10^(−1).研究发现辐射加热颗粒对流体的动力学调制加速了流体运动,使湍流强度增大.高辐射下的小Stokes数颗粒能显著加热流体.我们从流场时均温度方程出发,导出了两相流系统中相间传热Nusselt数的理论表达式,理论分析表明相间传热引起冷板和热板Nusselt数的差异,并进一步得到了相间传热效率与颗粒Stokes数及颗粒所受辐射强度的标度关系.

关键词：加热流体 Stokes数传热效率辐射加热辐射强度直接数值模拟拉格朗日点理论表达式

Effect of Stokes number on energy modulation of the fluid in turbulent particle-laden channel flows

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Journal of Hydrodynamics 2022年第3期34卷 510-521页

作者： Zhi-feng Wu Jian-zhao Wu Bo-fu Wang Zhi-ming Lu Shanghai institute of Applied Mathematics and mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai200072China

The effect of Stokes number on the kinetic energy(KE)budget in particle-laden turbulent channel flows is examined by conducting two-way coupled direct numerical simulations using the Eulerian-Lagrangian approach.The friction Reynolds number of the single phase channel flow is Re_(τ)=180,the particle mass loading and volume fraction areφ_(m)=0.2,φ_(v)≈10−4,and the Stokes numbers range from St^(+)=14–92.The statistics show that due to the presence of solid particles,the mean velocity is reduced in the vicinity of the wall but enhanced in the outer region,and the off-streamwise intensity of fluctuated velocity and the Reynolds stress are reduced in the whole channel.The analysis on the budgets of turbulent kinetic energy(TKE)finds that the presence of particles induces a significant reduction on both the production and dissipation rates.With increasing Stokes number St^(+),both the production and dissipation rates exhibit non-monotonical trends,i.e.,both initially decrease for St^(+)40.This suggests that the particle-induced suppression on TKE production and dissipation is the strongest nearly at St^(+)=40.It is also found that particles act as an additional sink/source term in the budgets of both mean-flow kinetic energy(MKE)and TKE.In addition,we investigate the influence of St^(+)on the“zero point”which indicates the balance of exchanging energy between the particle and fluid phases.It is shown that with increasing St^(+),the“zero point”moves toward the wall,suggesting that the position of perfect following between particle and fluid is closer to the wall with larger St^(+).The present results reveal the Stokes number effects on the spatial transport mechanisms of MKE,TKE in turbulent channel flows laden with inertial particles.

关键词： Particle-laden flows two-way coupling Stokes numbers kinetic energy budgets

粗糙表面和水平振动下Rayleigh-Benard揣流的大规模传热强化

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Acta Mechanica Sinica 2022年第2期38卷 60-67,I0002页

作者：吴建钊王伯福周全 Shanghai Key Laboratory of mechanics in Energy engineering Shanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China

本文在考虑粗糙度和外部振动条件下,对瑞利数范围10^(7)≤Ra≤10^(11)和振动频率范围0<ω<1400的Rayleigh-Benard对流(RBC)湍流进行了直接数值模拟.三角形粗糙单元均匀分布在顶面和底面上,并在水平方向上施加振动.结果表明,在粗糙度和... 详细信息

本文在考虑粗糙度和外部振动条件下,对瑞利数范围10^(7)≤Ra≤10^(11)和振动频率范围0<ω<1400的Rayleigh-Benard对流(RBC)湍流进行了直接数值模拟.三角形粗糙单元均匀分布在顶面和底面上,并在水平方向上施加振动.结果表明,在粗糙度和水平振动的共同作用下,随着振动频率ω的增加,传热最初略有降低,当ω超过临界值后,传热大大增强.大量传热强化的物理原因是高频振动使粗糙表面上的热边界层(BL)不稳定,触发大量热羽流的排放,并加强大尺度环流(LSC)的运动,从而使热边界层厚度变薄,对流输送增强.此外,研究还表明振动强化传热可以明显影响热流密度与瑞利数之间的标度行为,标度指数随ω的增加而增加;而振动对LSC强度和之间的标度行为的影响非常微弱.

关键词：水平振动粗糙表面热边界层标度行为传热强化高频振动物理原因标度指数

Tuning turbulent convection through rough element arrangement

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Journal of Hydrodynamics 2022年第2期34卷 308-314页

作者： Jian-zhao Wu Dao-liang Dong Bo-fu Wang Yu-hong Dong Quan Zhou Shanghai institute of Applied Mathematics and mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai200072China

The tuning of turbulent Rayleigh-Bénard(RB)convection in a box is realized numerically by designed rough element arrangement.Considering the nonlinear dynamics of the thermal turbulence system,five models with rough elements of different widths and the same height are proposed to tune the fluid flow heat-transport capacity.Numerical simulations are performed using spectral element method for Rayleigh number in the range 10^(6)≤Ra≤10^(9) and a fixed Prandtl number Pr=0.7.It is found that heat transport is enhanced for large roughness widths as the interaction between the large-scale circulation and secondary flows inside the cavity regions between the rough elements promotes the eruptions of thermal plumes,but is suppressed for small ones as more heat are trapped inside the cavities.In all the rough models studied,different scaling exponents for the heat transport are identified and the influences of roughness arrangement on flow structure are studied.

关键词： Rayleigh-Bénard(RB)turbulence heat transport roughness arrangement

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接地限幅型非线性能量汇

Acta Mechanica Sinica 2022年第5期38卷 135-146,I0003页

作者：耿晓锋丁虎毛晓晔陈立群 Shanghai Key Laboratory of mechanics in Energy engineering Shanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China

非线性能量汇(NES)以能量定向传输和共振自动捕获的特性在被动振动控制方面表现突出.为了提高实用性,本文提出了一种接地限幅型NES.该设计可以封装在一个盒子里.然而,由于NES的振动区域有限,需要考虑其控制效率.因此,通过近似解析方法... 详细信息

非线性能量汇(NES)以能量定向传输和共振自动捕获的特性在被动振动控制方面表现突出.为了提高实用性,本文提出了一种接地限幅型NES.该设计可以封装在一个盒子里.然而,由于NES的振动区域有限,需要考虑其控制效率.因此,通过近似解析方法、数值仿真方法,特别是强迫振动实验,研究接地限幅型NES的动力学特性.本研究中涉及的所有参数均通过基于实验平台的参数辨识得到.通过双曲正切函数将分段非线性拟合成连续非线性.然后在分析处理过程中使用谐波平衡法(HBM)来提高解的准确性.直接数值方法产生的结果与实验记录一起验证了解析方法.对控制参数的分析表明,适当的限位弹簧可以有效地降低NES的振动,同时控制效率的代价很小.总之,这项工作为NES的约束提供了一种简单可靠的方法,有利于NES的设计,拓宽了NES在工程中的应用.

关键词： Nonlinear energy sink Vibration suppression Piecewise nonlinearity Harmonic balance method

Thickness dependence of viscoelastic stress relaxation of laminated microbeams due to mismatch strain

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Applied Mathematics and mechanics(English Edition) 2022年第4期43卷 467-478页

作者： Xiaosheng CAI Nenghui ZHANG Hanlin LIU Shanghai institute of Applied Mathematics and mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China

Time-dependent behaviors due to various mismatch strains are very important to the reliability of micro-/nano-devices.This paper aims at presenting an analytical model to study the viscoelastic stress relaxation of the laminated microbeam caused by mismatch strain.Firstly,Zhang’s two-variable method is used to establish a mechanical model for predicting the quasi-static stress relaxation of the laminated microbeam.Secondly,the related analytical solutions are obtained by combining the differential method and the eigenvalue method in the temporal domain.Finally,the influence of the substrateto-film thickness/modulus ratio on the relaxation responses of the laminated microbeam subject to a step load of the mismatch strain is studied.The results show that the present predictions are consistent with the previous theoretical studies.Furthermore,the thickness dependence of stress relaxation time of the laminated microbeam is jointly determined by the intrinsic structural evolution factors and tension-bending coupling state;the stress relaxation time can be controlled by adjusting the substrate-to-film thickness/modulus ratio.

关键词： laminated structure stress relaxation mismatch strain tension-bending coupling effect analytical method

Dirac method for nonlinear and non-homogenous boundary value problems of plates

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Applied Mathematics and mechanics(English Edition) 2024年第1期45卷 15-38页

作者： Xiaoye MAO Jiabin WU Junning ZHANG Hu DING Liqun CHEN Shanghai Key Laboratory of mechanics in Energy engineering Shanghai Frontier Science Center of MechanoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China Shanghai institute of Aircraft mechanics and Control Shanghai 200092China

The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundary value problem of rectangular plates is proposed. The key concept behind this method is to transform the nonlinear or non-homogeneous part on the boundary into a lateral force within the governing function by the Dirac operator, which linearizes and homogenizes the original boundary, allowing one to employ the modal superposition method for obtaining solutions to reconstructive governing equations. Once projected into the modal space, the harmonic balance method(HBM) is utilized to solve coupled ordinary differential equations(ODEs)of truncated systems with nonlinearity. To validate the convergence and accuracy of the proposed Dirac method, the results of typical examples, involving nonlinearly restricted boundaries, moment excitation, and displacement excitation, are compared with those of the differential quadrature element method(DQEM). The results demonstrate that when dealing with nonlinear boundaries, the Dirac method exhibits more excellent accuracy and convergence compared with the DQEM. However, when facing displacement excitation, there exist some discrepancies between the proposed approach and simulations;nevertheless, the proposed method still accurately predicts resonant frequencies while being uniquely capable of handling nonuniform displacement excitations. Overall, this methodology offers a convenient way for addressing nonlinear and non-homogenous plate boundaries.

关键词： rectangular plate Dirac operator nonlinear boundary time-dependent boundary boundary value problem

Large-eddy simulation of turbulent boundary layer flow over multiple hills

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Journal of Hydrodynamics 2023年第4期35卷 746-756页

作者： Ying Deng Kai Leong Chong Yan Li Zhi-ming Lu Bo-fu Wang Shanghai Key Laboratory of mechanics in Energy engineering Shanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai200072China School of Aerospace engineering and Applied mechanics Tongji UniversityShanghai200092China

Atmospheric boundary layer(ABL)flow over multiple-hill terrain is studied numerically.The spectral vanishing viscosity(SVV)method is employed for implicit large eddy simulation(ILES).ABL flow over one hill,double hills,and three hills are presented in detail.The instantaneous three-dimensional vortex structures,mean velocity,and turbulence intensity in mainstream and vertical directions around the hills are investigated to reveal the main properties of this turbulent flow.During the flow evolution downstream,the Kelvin-Helmholtz vortex,braid vortex,and hairpin vortex are observed sequentially.The turbulence intensity is enhanced around crests and reduced in the recirculation zones.The present results are helpful for understanding the impact of topography on the turbulent flow.The findings can be useful in various fields,such as wind energy,air pollution,and weather forecasting.

关键词： Large-eddy simulation(LES) atmospheric boundary layer(ABL)flow complex terrain turbulent flow fields