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Effects of Material Characteristics on Thermal Stress around an Equiangular Polygonal Hole in a Thermoelectric Material 材料特性对热电材料等角多边形孔周围热应力的影响
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-03-24 DOI: 10.1093/jom/ufad003
M. Shen, Yi-Lun Liao, S. Tseng, C. Chao
In this study, we conducted a theoretical analysis of thermal stress around an arbitrarily-shaped hole in a thermoelectric material under electric current density and energy flux loading. Based on complex variable methods, conformal mapping, and analytical continuation theorem, the exact solutions of the thermal stress around a hole were obtained for the Seebeck coefficient and electric and heat conductivity. Based on the conversion efficiency equation of thermoelectric materials, higher electrical conductivity, and lower heat conductivity should be selected to achieve an optimal design. The theoretical results indicated that higher electrical conductivity could reduce the thermal stress around the hole. However, energy flux and thermal stress concentration might be generated around the adiabatic hole due to the presence of a matrix with lower heat conductivity. Hence, thermoelectric materials with lower thermal conductivity should be selected carefully to avoid premature failure around the hole caused by thermal stress concentration. Finally, we also obtained and discussed the stress intensity factors of a hypocycloid-type crack.
在本研究中,我们对电流密度和能量通量载荷下热电材料中任意形状孔洞周围的热应力进行了理论分析。基于复变法、保角映射和解析延拓定理,得到了塞贝克系数、电导率和导热系数的孔周热应力精确解。根据热电材料的转换效率方程,应选择电导率高、导热系数低的材料进行优化设计。理论结果表明,较高的电导率可以减小孔周围的热应力。然而,由于存在导热系数较低的基体,在绝热孔周围可能会产生能量通量和热应力集中。因此,应谨慎选择导热系数较低的热电材料,避免热应力集中导致孔周围过早失效。最后,我们还得到并讨论了次摆线型裂纹的应力强度因子。
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引用次数: 0
A direct numerical simulation method for solid-solid collision and coupling with fluid 固体-固体碰撞与流体耦合的直接数值模拟方法
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-03-03 DOI: 10.1093/jom/ufad001
Ming Yang, Ju-bao Liu, Y. Ding, Q. Yue, Qiang Zhang
The collision between solids in fluid is common in engineering, but the numerical simulation method is less studied. A direct numerical simulation method combining the sharp interface immersed boundary method and the finite element method based on penalty function was established for solid-solid collision and coupling with fluid. The lubrication model for cylinder structures with and without fluid flow was developed using the data regression method. The partitioned coupling algorithm was used to realize the coupling solution between the fluid and solid domains. Four numerical examples were presented to demonstrate the validity of the established method. The numerical simulation of the vortex-induced collisions between two side-by-side cylinders showed the capabilities of the proposed method.
流体中固体之间的碰撞在工程中很常见,但数值模拟方法研究较少。将锐界面浸入边界法和基于罚函数的有限元法相结合,建立了固-固碰撞与流体耦合的直接数值模拟方法。采用数据回归方法建立了有液流和无液流圆柱结构的润滑模型。采用分区耦合算法实现了流体与固体区域的耦合求解。通过四个算例验证了该方法的有效性。对两个并排圆柱体之间涡流诱导碰撞的数值模拟表明了该方法的能力。
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引用次数: 0
Computational Aerodynamics With Isogeometric Analysis 计算空气动力学与等几何分析
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-02-17 DOI: 10.1093/jom/ufad002
Y. Bazilevs, K. Takizawa, T. Tezduyar, A. Korobenko, T. Kuraishi, Yuto Otoguro
The superior accuracy isogeometric analysis (IGA) brought to computations in fluid and solid mechanics has been yielding higher fidelity in computational aerodynamics. The increased accuracy we achieve with the IGA is in the flow solution, in representing the problem geometry, and, when we use the IGA basis functions also in time in a space–time (ST) framework, in representing the motion of solid surfaces. It is of course as part of a set of methods that the IGA has been very effective in computational aerodynamics, including complex-geometry aerodynamics. The set of methods we have been using can be categorized into those that serve as a core method, those that increase the accuracy, and those that widen the application range. The core methods are the residual-based variational multiscale (VMS), ST-VMS, and arbitrary Lagrangian–Eulerian VMS methods. The IGA and ST-IGA are examples of the methods that increase the accuracy. The complex-geometry IGA mesh generation method is an example of the methods that widen the application range. The ST Topology Change method is another example of that. We provide an overview of these methods for IGA-based computational aerodynamics and present examples of the computations performed. In computational flow analysis with moving solid surfaces and contact between the solid surfaces, it is a challenge to represent the boundary layers with an accuracy attributed to moving-mesh methods and represent the contact without leaving a mesh protection gap.
等高几何分析(IGA)为流体和固体力学计算带来了更高的精度,在计算空气动力学中产生了更高的保真度。我们用IGA实现的精度提高是在流解中,在表示问题几何形状时,当我们在时空(ST)框架中使用IGA基函数时,在表示固体表面的运动时。当然,作为一系列方法的一部分,IGA在计算空气动力学方面非常有效,包括复杂几何空气动力学。我们一直在使用的方法可以分为核心方法、提高准确性的方法和扩大应用范围的方法。其核心方法是基于残差的变分多尺度(VMS)、ST-VMS和任意拉格朗日-欧拉VMS方法。IGA和ST-IGA是提高准确性的方法的例子。复杂几何IGA网格生成方法是拓宽应用范围的方法之一。ST拓扑更改方法是另一个例子。我们提供了这些方法的概述,以iga为基础的计算空气动力学和执行计算的实例。在具有移动实体表面和实体表面之间接触的计算流分析中,如何在不留下网格保护间隙的情况下准确地表示边界层是一个挑战。
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引用次数: 4
Influence on structure and fracture mechanics evaluations of a BWR feedwater nozzle following weld overlay repair 堆焊修复对沸水堆给水喷嘴结构及断裂力学评价的影响
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad008
Ru-Feng Liu, Ming-Chung Young
This present paper summarizes applying weld overlay repair on the feedwater nozzle in a boiling water reactor, and evaluates the influence on the structure and fracture mechanics of the component. The requirements for utilizing a full structural weld overlay, including the weld overlay design, effects of welding residual stresses (WRSs), impacts of weld shrinkage, prediction of potential flaw growth, and influence on ASME Code Section III design evaluations, are further defined in ASME Code Case N-504–2. In order to confirm the effectiveness of the weld overlay design of the nozzle, the WRSs following overlay installation were determined using engineering simulation software. The impacts of weld shrinkage from overlay welding are also addressed. The shrinkage stresses were evaluated via a numerical model of the attached piping system to ensure the design margins of the pipe structure. Since the weld overlay technique is well known to be effective in mitigating crack initiation or cracking to leakage, a fatigue crack growth prediction under ASME Code Section XI must be conducted to address the fatigue qualification of the affected component. The ASME Code Section III construction qualification of the whole nozzle region must consider the applicable thermal transient stresses, structural discontinuities, and bimetallic effects that are caused by the weld overlay. This investigation proves that the current stress analyses of the nozzle and the pipe structure are not significantly affected by the added overlay mass, so the structural integrity of the component can be ensured, meeting the requirements of ASME Code Case N-504–2.
本文综述了在沸水反应堆给水喷嘴上应用焊缝堆焊修复的情况,并对其对构件结构和断裂力学的影响进行了评价。使用完整的结构焊缝覆盖层的要求,包括焊缝覆盖层设计、焊接残余应力(wrs)的影响、焊缝收缩的影响、潜在缺陷生长的预测以及对ASME规范第III节设计评估的影响,在ASME规范案例N-504-2中有进一步的定义。为了验证喷管焊缝叠加设计的有效性,利用工程仿真软件确定了叠加后的wrs。还讨论了堆焊时焊缝收缩的影响。在保证管道结构设计裕度的前提下,通过附加管道系统的数值模型对收缩应力进行了评估。ASME规范第三部分对整个喷嘴区域的施工资格必须考虑适用的热瞬态应力、结构不连续和由焊缝覆盖引起的双金属效应。本次调查证明,增加的覆盖质量对喷管结构和管道结构的当前应力分析影响不大,可以保证构件的结构完整性,满足ASME规范案例N-504-2的要求。
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引用次数: 0
Simulation of unconfined seepage in soil–rock mixture slope by virtual element method 用虚元法模拟土石混合体边坡无侧限渗流
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad011
Yinghao Sun, Qi Yi, Jiao Wang, Guanhua Sun, Shan Lin
The virtual element method (VEM) is commonly used in engineering due to its ability to solve arbitrary node meshes. In this study, we propose a method to determine the free surface of the unconfined seepage problem in soil–rock mixtures slope using the advantages of the VEM. By cutting meshes in the iteration, our method overcomes the limitation of fixed mesh in solving the free surface, and the numerical tests confirm the accuracy of the proposed method in predicting the location of the seepage surface. Moreover, the results demonstrate that the presence of rock blocks significantly impacts the unconfined seepage behavior of soil–rock mixtures slope, revealing the importance of considering rock blocks in the analysis of such systems.
虚元法(VEM)因其具有求解任意节点网格的能力而在工程中得到广泛应用。在这项研究中,我们提出了一种利用向量机的优点来确定土石混合边坡无侧限渗流问题的自由面方法。通过在迭代中切割网格,克服了固定网格在求解自由面时的局限性,数值试验验证了该方法预测渗流面位置的准确性。此外,研究结果表明,岩石块体的存在显著影响土石混合边坡的无侧限渗流行为,揭示了在土石混合体系分析中考虑岩石块体的重要性。
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引用次数: 0
Preface Recent advances in isogeometric analysis 等几何分析的新进展
IF 1.7 4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufac051
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引用次数: 0
Pressure-sensitive paint measurements on the cavity with passive control devices under transonic flow 用无源控制装置对跨声速流腔进行压敏涂料测量
4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad023
Jun-Kai Ouyang, Yi-Ting Liao, Yen-Ting Hsu, Cheng-Chi Lee, Yu-Hung Lin, Chung-Lung Chen, Wei-Hsiang Wang
Abstract In this study, the pressure-sensitive paint (PSP) technique, specifically the mesoporous-particle-based PSP, was employed to compare rectangular cavities with varying length-to-depth ratios (L/D) and different trailing edge shapes under transonic conditions. By utilizing PSP, comprehensive and quantitative pressure data were obtained, enabling the simultaneous observation of surface flow field distribution. The results obtained using PSP were found to be consistent with those obtained from conventional pressure sensors. The study revealed that the pressure distribution within the cavities changed with increasing L/D, and cavities with different trailing edge shapes demonstrated a reduction in pressure at the bottom region. Furthermore, the comparison of results obtained through the oil flow method corroborated the PSP findings, indicating that a beveled or sawtooth-shaped trailing edge of the cavity induced air flow deflection, effectively disrupting the upstream shear flow structure and altering the pressure distribution at the cavityʼs bottom.
在本研究中,采用压敏涂料(PSP)技术,特别是基于介孔颗粒的PSP,在跨声速条件下比较了具有不同长深比(L/D)和不同尾缘形状的矩形空腔。利用PSP获得了全面、定量的压力数据,实现了对地表流场分布的同步观测。用PSP得到的结果与传统压力传感器得到的结果一致。研究发现,随着L/D的增加,空腔内压力分布发生变化,不同尾缘形状的空腔底部压力减小。此外,通过油流法得到的对比结果证实了PSP的发现,表明空腔的斜缘或锯齿形尾缘引起气流偏转,有效地破坏了上游剪切流结构,改变了空腔底部的压力分布。
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引用次数: 0
A numerical investigation of microtube length effect on convective boiling 微管长度对对流沸腾影响的数值研究
4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad029
Hua-Yi Hsu, Yu-Chen Lin, Zong-You Chen, Ying Wang, Cheng-En Li, Shong-Han Pai, Chia-Wei Lin
Abstract The microtube length significantly influences the convective boiling process and associated heat transfer characteristics. Other than high heat transfer, low pressure drop is also desired to improve the energy efficiency of the pumping system. This work numerically investigates the microtube length effect on heat transfer and pressure drops of convective boiling with the volume of fluid (VOF) method. The simulation results of vapor formation, heat transfer coefficient, and pressure drop are shown with different microtube lengths L = 2–20 mm. The onset of boiling is around 2 mm away from the mass flux inlet. The subcooled boiling regime can be observed between 2 and 10 mm. Three distinct regimes, liquid single-phase flow, bubbly flow, and plug flow, are shown in the longer microtubes (L = 15 mm and 20 mm). It is found that shorter microtubes can lead to less bubble formation with higher heat transfer and lower pressure drop. The average heat transfer coefficient can achieve 2432 W/(m2K) with a lower quasi-steady total pressure drop Δp|total of 32.8 Pa inside a 2-mm-long microtube. This work offers a detailed study of the impact of microtube length on convective boiling, along with pertinent physical insights. It may serve as an indicator for future microscale heat transfer application designs.
微管长度对对流沸腾过程及其传热特性影响显著。除了高传热,低压降也希望提高抽水系统的能源效率。本文采用流体体积法数值研究了微管长度对对流沸腾传热和压降的影响。给出了不同微管长度L = 2 ~ 20 mm时的蒸汽形成、换热系数和压降的模拟结果。沸腾发生在距离质量通量入口约2mm的地方。过冷沸腾状态可观察到2和10毫米之间。在较长的微管(L = 15 mm和20 mm)中显示了三种不同的状态,即液体单相流、气泡流和塞流。研究发现,微管越短,气泡形成越少,传热越好,压降越小。在2 mm长的微管内,平均换热系数可达到2432 W/(m2K),准稳态总压降Δp|总计32.8 Pa。这项工作提供了微管长度对对流沸腾的影响的详细研究,以及相关的物理见解。它可以作为未来微尺度传热应用设计的一个指标。
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引用次数: 0
An investigation on the evolution of strain localization zone in metallic materials based on tensile tests and a 1-D nonlocal model 基于拉伸试验和一维非局部模型的金属材料应变局部化区演化研究
4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad024
Wei Chen, Lizhi Xia, Yin Yao
Abstract Metallic materials exhibit pronounced strain localization during damage and failure, posing a challenge in damage mechanics when predicting the change in the size of the strain localization zone. In this study, uniaxial tensile tests were carried out to observe changes in the size of the strain localization zone during the loading of aluminum and low-carbon steel. The initial and final states of the two metallic materials during deformation localization were compared. The strain localization zone shrank gradually with the increase in the load, which agrees with existing electronic speckle pattern interferometry (ESPI) results. This experimental phenomenon was further analyzed theoretically. By establishing the relationship between the material characteristic length and the damage, the variation of the material characteristic length was revealed, and the form of the nonlocal kernel function with a varying characteristic length was determined. The results demonstrated that within the framework of nonlocal damage theory, the nonlocal kernel function with a varying characteristic length can be used to satisfactorily simulate the gradual shrinkage of the strain localization zone of metallic materials with the damage evolution. Therefore, this study provides an effective theoretical tool for predicting the size of the strain localization zone.
金属材料在损伤和失效过程中表现出明显的应变局部化,这对损伤力学中预测应变局部化区大小的变化提出了挑战。本研究通过单轴拉伸试验,观察铝和低碳钢加载过程中应变局部化区大小的变化。比较了两种金属材料在变形局部化过程中的初始状态和最终状态。随着载荷的增加,应变局部化区逐渐缩小,这与电子散斑干涉测量(ESPI)的结果一致。对这一实验现象进行了进一步的理论分析。通过建立材料特征长度与损伤之间的关系,揭示了材料特征长度的变化规律,确定了具有不同特征长度的非局部核函数的形式。结果表明,在非局部损伤理论框架下,采用变特征长度的非局部核函数可以较好地模拟金属材料应变局部化区随损伤演化的逐渐收缩。因此,本研究为预测应变局部化区大小提供了有效的理论工具。
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引用次数: 0
Analytical and numerical investigation on the effects of landslide acceleration in landslide-generated tsunamis 滑坡引发海啸中滑坡加速效应的分析与数值研究
4区 工程技术 Q2 Mathematics Pub Date : 2023-01-01 DOI: 10.1093/jom/ufad025
Peter H-Y Lo, I-Chi Chan
Abstract Submarine landslides are capable of causing locally catastrophic tsunamis. A landslide necessarily begins its motion by accelerating from a halt. However, the role of landslide acceleration on the tsunami generated by a landslide remains understudied. Assuming an idealized configuration, in this study we cast the landslide acceleration problem as an extension to the existing knowledge on landslide-generated tsunamis above a flat sea bottom. By using the Green’s function approach, we derived new analytical solutions for the tsunami generated by an accelerating submarine landslide. Consistent with the observations in existing studies, we found that a slower landslide acceleration results in a longer but smaller leading submarine landslide tsunami wave. Based on a large number of numerical simulations, empirical formulas were established to quantify the wave modification factors due to landslide acceleration. Combining existing analytical solutions and the newly determined empirical formulas, we assembled semi-analytical solutions that can be easily used to predict the characteristics of the tsunami generated by an accelerating submarine landslide.
海底滑坡能够引起局部灾难性的海啸。山体滑坡的运动必然是从静止加速开始的。然而,滑坡加速对滑坡引发的海啸的作用仍未得到充分研究。在本研究中,假设一个理想的配置,我们将滑坡加速问题作为对平坦海底以上滑坡引发的海啸的现有知识的扩展。通过使用格林函数方法,我们为加速海底滑坡产生的海啸导出了新的解析解。与已有研究的观测结果一致,我们发现滑坡加速度越慢,海底滑坡海啸波越长,但越小。在大量数值模拟的基础上,建立了量化滑坡加速度对波浪修正因子的经验公式。结合现有的解析解和新确定的经验公式,我们组装了半解析解,可以很容易地用于预测加速海底滑坡产生的海啸的特征。
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引用次数: 0
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Journal of Mechanics
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