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21.
Piotr Bogusaw Mucha Witold Sadowski 《Mathematical Methods in the Applied Sciences》2005,28(15):1867-1880
The paper analyses long time behaviour of solutions of the Navier–Stokes equations in a two‐dimensional pipe‐like domain. The system is studied with perfect slip boundary conditions with arbitrary inflow conditions at infinity. The main results show the existence of global in time solutions and of an attractor for the dynamical system generated by the model. The paper also establishes an upper bound for the Hausdorff dimension of the attractor. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
22.
利用非平衡分子动力学模拟方法, 模拟了两无限大平行平板组成的纳米通道内的库埃特流动, 并给出了壁面润湿性和速度对流场密度、速度分布及壁面滑移的影响规律.数值模拟中, 统计系综采用微正则系综, 势能函数选用LJ/126模型, 壁面设为刚性原子壁面, 温度校正使用速度定标法, 牛顿运动方程的求解则采用文莱特算法.结果表明, 纳米通道内流体密度呈对称的衰减振荡分布, 且随壁面润湿性的降低, 振荡幅度减小, 振荡周期保持不变;滑移量随壁面润湿性的提高而降低, 甚至在亲水壁面时出现负滑移现象;随壁面速度的增加滑移速度逐渐增大, 且在流体呈现非线性流动阶段其增幅显著加大.另外, 还发现当壁面设置为超疏水性时, 壁面滑移呈现出随润湿性降低而减小的反常现象, 并基于杨氏方程对其进行了解释. 相似文献
23.
Employing crystal plasticity theory and micromechanics inclusion theory, we developed a full-strain relaxation model under isotropic assumption of materials properties to predict the dependence of the critical shell thickness (CST) for defect-free core/shell nanowires (NWs) on their growth direction. Unlike prior models, we consider three important factors in the energetic analysis (1) the self-energy of a dislocation loop in a finite domain, (2) the three-dimensional mismatch strains that develop in core/shell NWs (axial, radial and tangential directions) as a result of the finite NW geometry and the lattice mismatch between the core and shell materials, and (3) the three-dimensional plastic strains from misfit dislocations that nucleate to relax the mismatch strains. With these, the full-relaxation model is able to reveal that (i) the variation of the CST with growth direction depends on the core radius, (ii) misfit dislocations will not nucleate when the core radius falls below a critical value, (iii) the CST tends to a constant as the core radius increases, and (iv) the CST predicted by prior uniaxial-strain relaxation models is a lower bound. 相似文献
24.
Pengxin Liu Zhangfeng Huang Hanxin Zhang 《International Journal of Computational Fluid Dynamics》2013,27(8-9):379-394
ABSTRACTIn studies on instabilities of flowfield in rotating detonation, one of the most common concerns is the instability at the slip line originating from the conjunction of the detonation wave and oblique shock. Using Euler equations associated with the 7-species-and-8-reaction finite-rate chemical reaction model of hydrogen/air mixtures, further studies are performed to simulate the 2-D rotating detonation, and the flow mechanism of instability at the slip line is investigated in depth. The results show that the distinct wake profile exists at the slip line, which is different from the typical mixing layer. Analysis indicates that the generation of wake is caused by the transition shock between the detonation wave and oblique shock. Because of the wake profile, the vorticity distribution therein appears in a double-layer layout, and different evolutions exist in different vorticity layers. Based on the velocity profile across the slip line, the analysis by the linear stability theory is made, and two main unstable modes which have different shape profiles and phase velocities are found. Discrete Fourier transformation is utilised to analyse the numerical results, and similar shape profiles are obtained. A general coincidence in velocity of vortex movement is also attained between the theoretical predictions and simulations. Investigations show that the wake instability is responsible for the unstable mechanism, and corresponding unstable structures differ from the canonical ones in typical mixing layers. 相似文献
25.
26.
页岩气和致密砂岩气藏微裂缝气体传输特性 总被引:3,自引:0,他引:3
页岩气和致密砂岩气藏发育微裂缝,其开度多在纳米级和微米级尺度且变化大,因此微裂缝气体传输机理异常复杂.本文基于滑脱流动和努森扩散模型,分别以分子之间碰撞频率和分子与壁面碰撞频率占总碰撞频率的比值作为滑脱流动和努森扩散的权重系数,耦合这两种传输机理,建立了微裂缝气体传输模型. 该模型考虑微裂缝形状和尺度对气体传输的影响. 模型可靠性用分子模拟数据验证.结果表明:(1)模型能够合理描述微裂缝中所有气体传输机理,包括连续流动,滑脱流动和过渡流动;(2)模型能够描述不同开发阶段,微裂缝中各气体传输机理对传输贡献的逐渐变化过程;(3)微裂缝形状和尺度影响气体传输,相同开度且宽度越大的微裂缝,气体传输能力越强,且在高压和微裂缝大开度的情况下表现更明显. 相似文献
27.
Guangwu Wang Boling Guo Shaomei Fang 《Mathematical Methods in the Applied Sciences》2017,40(14):5262-5272
In this paper, we will firstly extend the results about Jiu, Wang, and Xin (JDE, 2015, 259, 2981–3003). We prove that any smooth solution of compressible fluid will blow up without any restriction about the specific heat ratio γ. Then we prove the blow‐up of smooth solution of compressible Navier–Stokes equations in half space with Navier‐slip boundary. The main ideal is constructing the differential inequality. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
28.
Piotr Kacprzyk 《Mathematical Methods in the Applied Sciences》2013,36(3):313-322
Global existence of regular solutions to the Navier–Stokes equations coupled with the heat convection in a cylindrical pipe has already been shown. In this paper, we prove the existence of the global attractor to the equations and convergence of their solutions to a stationary one. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
29.
Jules K. Djoko Virginie S. Konlack Mohamed Mbehou 《Numerical Methods for Partial Differential Equations》2020,36(1):86-117
In this work, we consider the heat equation coupled with Stokes equations under threshold type boundary condition. The conditions for existence and uniqueness of the weak solution are made clear. Next we formulate the finite element problem, recall the conditions of its solvability, and study its convergence by making use of Babuska–Brezzi's conditions for mixed problems. Third we formulate an Uzawa's type iterative algorithm that separates the fluid from heat conduction, study its feasibility, and convergence. Finally the theoretical findings are validated by numerical simulations. 相似文献
30.
Influence of cross diffusions on mixed convection chemical reaction flow in a vertical channel with Navier slip: Homotopy approach 下载免费PDF全文
This paper is to examine the incompressible, laminar mixed convective Navier slip flow between vertical plates with cross diffusion effects. This research includes the first order chemical reaction also. The resulting equations with boundary conditions are reduced into dimensionless form using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The influence of emerging parameters on fluid flow quantities have been presented graphically. Also, the nature of physical quantities are shown in tabular form. 相似文献