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Numerical investigation on the nanofluids heat transfer inside a porous inclined cavity with wavy boundary 波浪边界多孔倾斜腔内纳米流体传热的数值研究
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-12-16 DOI: 10.24423/AOM.3550
B. Karimi, M. Pirmohammadi, A. Salehi-Shabestari
In the present work, a numerical study on the free-convective heat transfer in a porous media cavity with a wavy boundary was carried out. The validation was done by comparing the results with the experimental data. The cavity inclination angle, material of nanofluid, nanoparticles volume fraction, the Rayleigh number, and porosity of the medium are the parameters which are investigated in this study. Results suggested that, due to the thermophysical properties of Cu particles in water, the heat transfer rate was increased for Cu-Water nanofluid in comparison to Al 2 O 3 -Water nanofluid, while the heat transfer rate decreased by increasing the volume fraction of nanoparticles. Numerical results showed that the Rayleigh number has significant effect on the heat transfer rate so that increase in the Rayleigh number from 100 to 10 000 increased the averaged Nusselt number between 2 to 3 times. The effect of porosity on heat transfer proved that the convective heat transfer rate increased with increasing the porosity of the porous medium. The effect of inclination angle of cavity on the heat transfer rate suggested that the optimum angle of cavity causing the highest heat transfer rate from wavy wall is 45°.
本文对具有波浪边界的多孔介质腔内的自由对流换热进行了数值研究。通过与实验数据的比较,验证了该方法的有效性。研究了空腔倾角、纳米流体材料、纳米颗粒体积分数、瑞利数和介质孔隙度等参数。结果表明,由于Cu颗粒在水中的热物理性质,Cu-Water纳米流体的传热速率比Al 2o3 -Water纳米流体高,而随着纳米颗粒体积分数的增加,传热速率降低。数值结果表明,瑞利数对换热速率有显著影响,瑞利数从100增加到10000,平均努塞尔数增加2 ~ 3倍。孔隙率对传热的影响表明,多孔介质的对流换热率随着孔隙率的增大而增大。腔体倾角对换热率的影响表明,腔体倾角为45°时,波壁换热率最高。
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引用次数: 0
The effect of temperature-dependent viscosity and thermal conductivity on velocity and temperature field: an analytical solution using the perturbation technique 温度依赖性粘度和热导率对速度和温度场的影响:用微扰技术的解析解
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-12-16 DOI: 10.24423/AOM.3618
H. Panahi-Kalus, M. Ahmadinejad, A. Moosaie
This paper proposes a general form of the perturbation expansion method for the governing equations of viscous flow coupled to the temperature evolution. The effect of the variations of viscosity and thermal conductivity with temperature on the temperature and velocity fields in a steady two-dimensional Couette–Poiseuille flow is examined. The presented analytical solution by the perturbation method is validated against a finite difference solution of the governing equations. The numerical and analytical solutions are in good agreement.
本文提出了含温度变化的粘性流动控制方程的摄动展开法的一般形式。研究了稳态二维库埃-泊叶流动中粘度和导热系数随温度的变化对温度场和速度场的影响。用摄动法对控制方程的有限差分解进行了验证。数值解与解析解吻合较好。
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引用次数: 4
Assessment of mechanical properties of bone trabeculae as an inverse problem of heterogeneous material modeling 作为非均质材料建模的反问题评估骨小梁的力学性能
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-10-19 DOI: 10.24423/AOM.3469
K. Janc, J. Tarasiuk, P. Lipinski, A. Bonnet, S. Wronski
In this study, the trabecular bone was treated as a composite material that consists of a bone matrix weakened by ellipsoidal pores. Under the hypothesis that all information concerning the local properties and the microarchitecture are “encrypted” in the apparent properties of a given volume element (VE) of the bone, a method of retrieving these data was proposed. Software based on a genetic algorithm, combined with the incremental scale transition method was developed to this end. To test the approach, μCT measurements of four bone samples were performed providing their real micro-architecture. Tensors of apparent properties of the samples were next computed by numerical (finite element) homogenization method for a large range of the elastic properties of trabeculae. They were considered as the fitness function for the proposed algorithm. Very good agreement was found between the obtained and target values of the apparent elastic properties of the samples and volume fraction of pores. The approach is fast and accurate enough in comparison to the finite element homogenization. As an auxiliary result it was shown that the anisotropy of apparent elastic properties is mainly related to the microarchitecture of the bone, not to the intrinsic properties of trabeculae.
在这项研究中,小梁骨被视为一种复合材料,由被椭球孔削弱的骨基质组成。在假设所有关于局部特性和微结构的信息都在给定骨体积元素(VE)的表观特性中“加密”的情况下,提出了一种检索这些数据的方法。为此,开发了基于遗传算法并结合增量尺度转换方法的软件。为了测试该方法,对四个骨骼样本进行了μCT测量,以提供其真实的微观结构。接下来,对于小梁的大范围弹性特性,通过数值(有限元)均匀化方法计算样品的表观特性张量。它们被认为是所提出算法的适应度函数。在样品的表观弹性性质和孔隙体积分数的所获得的值和目标值之间发现了非常好的一致性。与有限元均匀化方法相比,该方法足够快速和准确。辅助结果表明,表观弹性特性的各向异性主要与骨的微结构有关,而与小梁的固有特性无关。
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引用次数: 2
A new dynamic model for a rotating beam carrying extra partially distributed mass 一种带有额外部分分布质量的旋转梁的新动力学模型
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-10-08 DOI: 10.24423/AOM.3498
A. Altınkaynak, M. Gürgöze
In this paper, a new dynamic model for the vibration analysis of an inwardoriented rotating cantilever beam with extra distributed mass was presented. The derived differential equation of motion was solved using the meshless methods of generalizedMultiquadric Radial Basis Function (RBF) and the eigenfrequencies of the system were determined. The same problem was also modeled using the finite element method and the results were compared to validate the accuracy of the proposed model. Later, the effect of the partially distributed mass amount and location on the eigenfrequencies was studied for various beam lengths. The results showed that the eigenfrequency at a constant rotational speed mostly decreased unless the mass was located at the free end of the beam. The location of the mass had a greater effect on the first eigenfrequency compared to the second and third eigenfrequencies. A joint dimensionless eigenfrequency was found at a specific rotational speed regardless of the distributed mass. Nearly constant dimensionless eigenfrequencies could be obtained for a wide range of rotational speeds by adjusting the distributed mass.
本文提出了一种新的动力学模型,用于分析具有额外分布质量的向内旋转悬臂梁的振动。利用广义二次径向基函数(RBF)的无网格方法求解导出的运动微分方程,确定了系统的本征频率。同样的问题也使用有限元方法进行了建模,并对结果进行了比较,以验证所提出模型的准确性。随后,研究了不同光束长度下部分分布的质量量和位置对本征频率的影响。结果表明,在恒定转速下,除非质量位于梁的自由端,否则本征频率大多会降低。与第二和第三本征频率相比,质量的位置对第一本征频率具有更大的影响。在特定转速下,无论分布质量如何,都会发现联合无量纲本征频率。通过调整分布质量,可以在宽转速范围内获得几乎恒定的无量纲本振频率。
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引用次数: 0
Nanofluid flow and heat transfer of carbon nanotube and graphene platelette nanofluids in entrance region of microchannels 碳纳米管和石墨烯板纳米流体在微通道入口区域的流动和传热
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-10-08 DOI: 10.24423/AOM.3556
M. Fuller, J. Liu
Suspensions of nano-scale particles in liquids, dubbed nanofluids, are of great interest for heat transfer applications. Nanofluids potentially offer superior thermal conductivity to alternative, pure fluids and are of particular interest in applications where active cooling of power-dense systems is required. In this work, the thermophysical properties of carbon nanotube nanofluids (CNTNf) and those of graphene nanoplatelette nanofluids (GNPNf) as functions of particle volume fraction are deduced from published experiments. These properties are applied to a perturbative boundary layer model to examine how the velocity and temperature profiles (and correspondingly shear stress and surface heat transfer) vary with the nanoparticle concentration in the entrance region of microchannels. Findings of this modeling effort indicate that both shear stress and heat transfer in GNPNf increase with increasing particle concentration. The normalized increase in shear stress is approximately twice that for heat transfer as a function of the GNP particle concentration. Interestingly, CNTNf shows anti-enhancement heat transfer behaviour; an increasing concentration of CNT nanoparticles is associated with both an increase in shear stress and a decrease in the surface heat transfer rate.
纳米颗粒在液体中的悬浮液,被称为纳米流体,对传热应用非常感兴趣。纳米流体可能比替代的纯流体具有更高的导热性,并且在需要对功率密集系统进行主动冷却的应用中特别令人感兴趣。在这项工作中,从已发表的实验中推导了碳纳米管纳米流体(CNTNf)和石墨烯纳米板纳米流体(GNPNf)的热物理性质作为颗粒体积分数的函数。将这些特性应用于微扰边界层模型,以检查速度和温度分布(以及相应的剪切应力和表面传热)如何随着微通道入口区域中的纳米颗粒浓度而变化。该建模工作的结果表明,GNPNf中的剪切应力和传热都随着颗粒浓度的增加而增加。作为GNP颗粒浓度的函数,剪切应力的归一化增加大约是传热的两倍。有趣的是,CNTNf表现出抗增强传热行为;CNT纳米颗粒浓度的增加与剪切应力的增加和表面热传递速率的降低都相关。
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引用次数: 1
Analysis of multiple bifurcation behavior for periodic structures 周期结构的多重分岔行为分析
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-10-08 DOI: 10.24423/AOM.3433
I. Ario, M. Nakazawa
The classification of simple singularities in the post-buckling analysis of truss structures is well-known for elastic stability. To focus on multiple singularities including a hilltop bifurcation point (h-BP) and its bifurcation paths, we reviewed the multiple bifurcation analysis of multi-folding microstructure (MFM) models with periodic symmetry. Because the Jacobian at the h-BP of the MFM involves multiple 0-eigenvalues, it is challenging to analyse the bifurcation paths from the h-BP accurately. In this study, we investigated the multiple folding mechanism by analysing the neighbourhood of the h-BP and the symmetric subgroups of the geometric system in the two-dimensional plane and three-dimensional core of the MFM. We demonstrated that through the classification of multiple h-BP and bifurcation paths, it is possible to determine the unknown bifurcation equilibrium paths following h-BP, based on the Jacobian stability and the mechanism of symmetric subgroups in group theory containing the relationships between the primary path and the known bifurcation path(s) in the MFM system with periodic symmetry.
在桁架结构的后屈曲分析中,简单奇异点的分类是众所周知的弹性稳定性问题。针对包括山顶分岔点(h-BP)在内的多奇异点及其分岔路径,综述了具有周期对称性的多折叠微结构(MFM)模型的多分岔分析。由于MFM的h-BP处的雅可比矩阵包含多个0特征值,因此从h-BP处准确分析分叉路径具有挑战性。在本研究中,我们通过分析二维平面和三维核心中的h-BP和几何系统的对称子群的邻域来研究多重折叠机制。基于Jacobian稳定性和群论中包含主路径与已知分岔路径关系的对称子群机制,证明了通过对多个h-BP和分岔路径的分类,可以确定具有周期对称性的MFM系统中h-BP之后的未知分岔平衡路径。
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引用次数: 1
Non-linear modelling of elastic hysteretic damping in the time domain 弹性滞回阻尼的时域非线性建模
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-10-08 DOI: 10.24423/AOM.3536
C. Spitas, M. Dwaikat, V. Spitas
Elastic hysteretic damping is defined as the dissipation of energy at a rate that is weakly dependent on frequency of vibration. In this article, we propose that the elastic hysteretic damping can be achieved by a simple modification to the viscous damping model. The proposed modification is based on computing an instantaneous correction factor that recursively depends on the state variables of the system. This correction factor is related to the rate by which the velocity changes with respect to the displacement. The new model compares quite favourably with the other existing solutions in the time-domain and differences between the solutions become evident for higher damping ratios. It is found that the new model predicts consistently the weak variation in the loss factor as a function of frequency. In addition to its simple mathematical formulation, the proposed model is superior to the existing solutions in that it does not require knowledge of the past history of motion neither the knowledge of the excitation frequency and is extensible to any type of loading. Various aspects pertaining to the linearity of the proposed approach are finally discussed.
弹性滞回阻尼的定义是能量的耗散速率与振动频率的关系很弱。在本文中,我们提出弹性滞回阻尼可以通过对粘性阻尼模型的简单修改来实现。所提出的修正是基于计算一个递归依赖于系统状态变量的瞬时修正因子。这个修正系数与速度相对于位移的变化率有关。新模型在时域上与其他现有的解相比非常有利,并且在较高的阻尼比下,解之间的差异变得明显。结果表明,新模型能较好地预测损耗因子随频率的微弱变化。除了其简单的数学公式外,所提出的模型优于现有的解决方案,因为它不需要了解过去的运动历史,也不需要了解激励频率,并且可以扩展到任何类型的加载。最后讨论了与所提出的方法的线性有关的各个方面。
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引用次数: 9
Formulas for the slowness of Stoneley waves with sliding contact 具有滑动接触的斯通利波慢度公式
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-09-23 DOI: 10.24423/AOM.3612
P. Giang, P. C. Vinh, V. Anh
The main aim of this paper is to derive formulas for the slowness of Stoneley waves traveling along the sliding interface of two isotropic elastic half-spaces. These formulas have been obtained by employing the complex function method. From the derivation of them, it is shown that if a Stoneley wave exists, it is unique. Based on the obtained formulas, it is proved that a Stoneley wave is always possible for two isotropic elastic half-spaces with the same bulk wave velocities. This result leads to the fact that a Stoneley wave is always possible for two elastic half-spaces satisfying the Wiechert condition, a condition that plays an important role in acoustic analyses. The obtained formulas are of theoretical interest and they will be useful in practical applications, especially in nondestructive evaluations.
本文的主要目的是推导出沿两个各向同性弹性半空间滑动界面传播的斯通利波慢度的计算公式。这些公式是用复变函数法得到的。通过对它们的推导,证明了如果存在斯通利波,那么它是唯一的。根据所得公式,证明了具有相同体波速的两个各向同性弹性半空间总是可能存在斯通利波。这一结果导致两个满足Wiechert条件的弹性半空间总是可能存在斯通利波,这一条件在声学分析中起着重要作用。所得公式不仅具有理论意义,而且在实际应用中,特别是在无损评价中具有实用价值。
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引用次数: 1
Integro-differential form of the first-order dual phase lag heat transfer equation and its numerical solution using the Control Volume Method 一阶双相滞后传热方程的积分-微分形式及其控制体积法的数值解
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-07-10 DOI: 10.24423/AOM.3555
M. Ciesielski, B. Mochnacki, E. Majchrzak
The start point of the dual phase lag equation (DPLE) formulation is the generalized Fourier law in which two positive constants (the relaxation and thermalization times) appear. This type of equation can be used (among others) to describe the heat conduction processes proceeding in micro-scale. Depending on the number of components in the development of the generalized Fourier law into a power series, one can obtain both the first-order DPLE and the second-order one. In this paper the first-order dual phase lag equation is considered. The primary objective of this research is the transformation of DPLE differential form to the integro-differential one supplemented by the appropriate boundary-initial conditions. The obtained form of the differential equation is much simpler and more convenient at the stage of numerical computations – the numerical algorithm based on the three-time-level scheme reduces to the two-time-level one. To find the numerical solution, the Control Volume Method is used (the heating of thin metal film subjected to a laser beam is considered). The choice of the numerical method was not accidental. The method has a simple physical interpretation ensuring the preservation of the local and global energy balances. To our knowledge, it has not been used so far in this type of tasks. In the final part of the paper the examples of numerical simulations are presented and the conclusions are formulated.
双相滞后方程(DPLE)的出发点是出现两个正常数(弛豫时间和热化时间)的广义傅立叶定律。这种类型的方程可以用来(除其他外)描述在微观尺度上进行的热传导过程。根据将广义傅里叶定律发展成幂级数的分量数量,可以得到一阶DPLE和二阶DPLE。本文考虑一阶双相位滞后方程。本研究的主要目的是将DPLE微分形式转化为补充适当的边界初始条件的积分微分形式。得到的微分方程形式在数值计算阶段更加简单和方便——基于三时间级格式的数值算法简化为两时间级格式。为了求出数值解,采用了控制体积法(考虑了激光束对金属薄膜的加热)。数值方法的选择不是偶然的。该方法具有简单的物理解释,确保了局部和全局能量平衡的保存。据我们所知,到目前为止还没有在这类任务中使用它。在论文的最后部分给出了数值模拟的实例,并给出了结论。
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引用次数: 4
Misfit dislocation in a precipitate/matrix interface of any orientation relative to the matrix free-surface 在相对于基体自由表面的任意取向的沉淀/基体界面上的错位
IF 0.8 4区 工程技术 Q3 Engineering Pub Date : 2020-07-10 DOI: 10.24423/AOM.3590
J. Colin
The presence of an edge dislocation in a surface of a two-dimensional precipitate of square shape embedded in a semi-infinite matrix has been discussed when the precipitate is submitted to misfit strain due to the lattice mismatch between the two phases. Considering any orientation of the precipitate relative to the matrix free-surface, the total force applying on the dislocation has been analytically calculated and its equilibrium position has been determined. The conjugated effects of the precipitate misorientation, of the lattice mismatch and of the precipitate/matrix distance have been finally characterized. A shifting effect on this equilibrium position has been analyzed.
本文讨论了镶嵌在半无限基体中的二维方形析出物由于两相晶格失配而产生失配应变时,析出物表面出现边缘位错的问题。考虑析出相相对于基体自由表面的任意取向,分析计算了施加在位错上的总力,并确定了位错的平衡位置。最后对析出相取向错误、晶格失配和析出相/基体距离的共轭效应进行了表征。分析了位移对平衡位置的影响。
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引用次数: 0
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Archives of Mechanics
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