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Investigating the Impact of Flow Profile on Heat Transfer in Nanofluid Flow: A Numerical Study 纳米流体流动中流动剖面对传热影响的数值研究
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34638
B. Litouche, Billel Rebai, Khelifa Mansouri
Assessing the profitability of an energy system requires careful consideration of various factors, including fluid characteristics, geometry shape, and operating conditions. This study investigates the influence of sinusoidal rib shapes, with different space ratios (e/b) ranging from 0 to 1, on heat transfer in nanofluid flow. The channel's upper surface is subjected to a uniform heat flux, employing Al2O3 nanofluid as the working fluid and varying Reynolds numbers from 5000 to 20000. Additionally, the effect of aluminum nanoparticle volume fraction, ranging from 0 to 6%, is analyzed. Simulation results indicate that the performance of the corrugated surface in the channel is significantly influenced by rib shapes and their geometrical parameters. The highest Performance Evaluation Criteria (PEC) index is achieved for ribs with a space ratio (e/b) of 0 at Reynolds number of 5000 and a volume fraction of 6% nanoparticles. Furthermore, the average Nusselt number shows an increasing trend with higher particle volume fraction and Reynolds numbers.
评估能源系统的盈利能力需要仔细考虑各种因素,包括流体特性、几何形状和运行条件。本研究探讨了不同空间比(e/b)(从 0 到 1)的正弦肋形状对纳米流体流动传热的影响。采用 Al2O3 纳米流体作为工作流体,雷诺数从 5000 到 20000 不等,通道上表面受到均匀热通量的影响。此外,还分析了铝纳米粒子体积分数(0 至 6%)的影响。模拟结果表明,通道中波纹表面的性能受肋条形状及其几何参数的影响很大。在雷诺数为 5000 和纳米颗粒体积分数为 6% 时,空间比 (e/b) 为 0 的肋条的性能评估标准 (PEC) 指数最高。此外,随着颗粒体积分数和雷诺数的增加,平均努塞尔特数也呈上升趋势。
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引用次数: 0
Vibration Analysis of Porous Functionally Graded Material Truncated Conical Shells in Axial Motion 轴向运动中多孔功能分级材料截顶锥壳的振动分析
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34592
Weiwei Xiao, Siqi Liu, Xiaolin Huang, Xiaojun Wu, Xusheng Yuan
In this study, a vibration equation for axially moving truncated conical thin shells made of functionally gradient materials with uniformly and non-uniformly distributed pores has been established based on classical thin shell theory. The free vibration and dynamic response solutions are obtained using the Galerkin method. The effects of axial velocity, half cone angle, ceramic material mass composition, material component index, and internal porosity on the free vibration and dynamic response of mentioned shells were analyzed and discussed. The results show that the increase of axial velocity, half cone angle, and material composition index all decrease the natural frequency of the truncated conical shell but amplify its dynamic response, and the rise of the mass fraction of the ceramic material increases the natural frequency of the truncated conical shell but reduces the dynamic response. The results also demonstrate that compared with non-uniformly distributed pores, the effects of uniformly distributed pores on the shells’ dynamic responses are more evident under axial motion.
本研究以经典薄壳理论为基础,建立了由均匀和非均匀分布孔隙的功能梯度材料制成的轴向移动截顶锥形薄壳的振动方程。采用 Galerkin 方法获得了自由振动和动态响应解。分析并讨论了轴向速度、半锥角、陶瓷材料质量成分、材料成分指数和内部孔隙率对所述壳体自由振动和动态响应的影响。结果表明,轴向速度、半锥角和材料成分指数的增加都会降低截顶锥形壳的固有频率,但会放大其动态响应;陶瓷材料质量分数的增加会提高截顶锥形壳的固有频率,但会降低其动态响应。结果还表明,与非均匀分布孔隙相比,均匀分布孔隙在轴向运动下对壳体动态响应的影响更为明显。
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引用次数: 0
Effects of Weld Heat Input on Mechanical Characteristics of Low Carbon Sheet Steels 焊接热输入对低碳薄板钢机械特性的影响
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34356
S. O. Eruslu, Ismail Berk Akbulut, I. Dalmis
This study focuses on examining the variation in mechanical characteristics of low-carbon sheet steels when they are subjected to heat input from Tungsten Inert Gas (TIG) welding. The weld heat input parameters, such as welding speed and current, were controlled through the TIG welding process. A finite element analysis was performed to evaluate the couple field thermomechanical effects of the weld heat line, using the Gauss heat flux approach for thermal heat variation across the weld heat-affected zone. The numerical study yielded results for weld heat-affected deflection, residual stress, and modal analysis through the finite element model. It was found that the ductility decreased and hardness increased in the fusion zone, as a function of weld current and speed. The residual stresses and their zone of influence, as determined by weld line parameters, were found to be key factors affecting deflection and natural frequencies in structural aspects of low carbon sheet steels.
本研究主要探讨低碳薄板钢在钨极惰性气体(TIG)焊接热输入作用下的机械特性变化。通过 TIG 焊接过程控制焊接热输入参数,如焊接速度和电流。采用高斯热通量法对整个焊接热影响区的热量变化进行了有限元分析,以评估焊接热线的耦合场热机械效应。数值研究通过有限元模型得出了焊缝热影响挠度、残余应力和模态分析的结果。研究发现,随着焊接电流和速度的变化,熔合区的延展性降低,硬度增加。研究发现,由焊接线参数决定的残余应力及其影响区域是影响低碳薄板钢结构挠度和固有频率的关键因素。
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引用次数: 0
Averaged Heat Fluxes Densities During Condensation and Evaporation of a Water Droplet 水滴凝结和蒸发过程中的平均热通量密度
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.35522
Kristina Biknienė, L. Paukštaitis
This study is intended for experimental investigation of the influence of boundary conditions on the intensity of phase transformations and heat transfer processes in  a suspended water droplet. The results of the dynamics of the averaged heat fluxes densities during the droplet phase change cycle are presented and analysed. The influence of the droplet initial temperature, the surrounding air flow temperature and the additional humidity in the air flow were defined in separate regimes of the droplet phase transformations cycle. The  experiments performed demonstrated that the parameters of the air flow surrounding the suspended water droplet affect the intensity of heat fluxes in the droplet throughout whole its phase change cycle. It was experimentally claimed that the initial temperature of the water droplet has no influence on the droplet heat and mass transfer processes in the equilibrium evaporation regime. The obtained results showed that most intensity heat flux densities are at the beginning of the droplet phase change cycle when condensation process occurs on the droplet’s surface in case with biggest amount of additional humidity in the surrounding air flow. This is very important in technologies of cleaning and heat recovery from flue gases.
本研究旨在通过实验研究边界条件对悬浮水滴中相变强度和传热过程的影响。研究介绍并分析了水滴相变周期中平均热通量密度的动态变化结果。在水滴相变周期的不同阶段,确定了水滴初始温度、周围气流温度和气流中额外湿度的影响。实验证明,悬浮水滴周围的气流参数会影响水滴在整个相变周期中的热通量强度。实验证明,在平衡蒸发状态下,水滴的初始温度对水滴的传热和传质过程没有影响。实验结果表明,在周围气流附加湿度最大的情况下,水滴相变周期开始时的热流密度最大,此时水滴表面发生凝结过程。这对烟气清洁和热回收技术非常重要。
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引用次数: 0
Effect of Structural Parameters on the Jet Formation and Penetration Capability of Small Caliber Shaped Charges 结构参数对小口径异形装药射流形成和穿透能力的影响
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.32649
Yongjie Xu, Xiaodong Wang, Wenhui XIE, Nana Zheng
Take small caliber high explosive antitank cartridge as research platform, establish 35mm diameter warhead model. Numerical simulation for the process of shaped charge jet forming and penetrating the target has been done through explosion mechanics analysis software AUTODYN. Effect of liner thickness, cone angle and charging length-diameter ratio on shaped charge jet performance has been analyzed. And the optimal combination of the structural parameters of the shaped charge has been determined by orthogonal optimum design. Results show that optimized shaped charge structure can penetrate 105mm steel target under simulation conditions and the maximum penetration depth of main charge in the explosion test is 100mm, the average value of penetration depth is 86.67mm. The minimum and average of relative error between results of static explosion test and numerical simulation are 4.76% and 17.46% respectively. The research results can provide theoretical and technical support for the optimization design and engineering application of small caliber shaped charge.
以小口径高爆反坦克弹为研究平台,建立直径 35 毫米的弹头模型。通过爆炸力学分析软件 AUTODYN 对定型装药射流形成和穿透目标的过程进行了数值模拟。分析了衬垫厚度、锥角和装药长径比对定型装药射流性能的影响。并通过正交优化设计确定了定型装药结构参数的最佳组合。结果表明,优化后的异形装药结构在模拟条件下可穿透 105mm 钢靶,爆炸试验中主装药的最大穿透深度为 100mm,穿透深度的平均值为 86.67mm。静爆试验结果与数值模拟结果的最小相对误差为 4.76%,平均相对误差为 17.46%。研究成果可为小口径定型装药的优化设计和工程应用提供理论和技术支持。
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引用次数: 0
Research on Complementary Filtered Attitude Solution Method for Quadcopter Based on Double Filter Preprocessing 基于双重滤波预处理的四旋翼飞行器互补滤波姿态解算方法研究
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34093
Linlin Zhang, Haoyu ZHOU, Jianshu Liang, Meng Xie, Guang Yang
In the attitude calculation process of quadrotor, the traditional pre-filtering method has degraded the attitude solving accuracy due to incomplete denoising of accelerometer and gyroscope measurements. Therefore, a complementary filtered attitude solution method based on double filter pre-processing is proposed to address this problem. First, the signal decomposition, hard threshold denoising, and signal reconstruction of the accelerometer and gyroscope acquired data are performed using the Haar real-time wavelet filtering algorithm. The reconstructed signal is then filtered by the infinite impulse response ( IIR ) low-pass filtering algorithm to remove the residual high-frequency noise and complete the dual filtering preprocessing. Next, the gyroscope data is corrected with accelerometer data according to the complementary filtering algorithm. Finally, the corrected data are used to solve the quaternion and thus the attitude angle by combining the Longacurta method. The results show that the dual filtering preprocessing method can further reduce the noise in the measurements of accelerometer and gyroscope. The attitude angle results calculated by the proposed method in the static and dynamic hovering states of the four-rotor aircraft have a small degree of dispersion, which can effectively improve the accuracy of attitude calculation.
在四旋翼飞行器的姿态计算过程中,由于加速度计和陀螺仪测量值去噪不彻底,传统的预滤波方法降低了姿态解算精度。因此,针对这一问题,提出了一种基于双滤波预处理的互补滤波姿态求解方法。首先,使用 Haar 实时小波滤波算法对加速度计和陀螺仪采集的数据进行信号分解、硬阈值去噪和信号重构。然后用无限脉冲响应(IIR)低通滤波算法对重建后的信号进行滤波,以去除残留的高频噪声,完成双重滤波预处理。接着,根据互补滤波算法,用加速度计数据校正陀螺仪数据。最后,利用校正后的数据求解四元数,并结合 Longacurta 方法求解姿态角。结果表明,双重滤波预处理方法可以进一步降低加速度计和陀螺仪测量值中的噪声。在四旋翼飞行器的静态和动态悬停状态下,所提出的方法计算出的姿态角结果具有较小的离散度,能有效提高姿态计算的精度。
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引用次数: 0
Physical-Model-Based Assessment of Reduction of Hydraulic Forces Acting on Channel Bed through Advanced Energy Dissipator Design 基于物理模型的评估:通过先进的消能设计减少作用于河床的水力
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.33307
Petr Štemberk, M. Petřík, Jan Edlák, Milan Zukal, Tomas Picek
The hydraulic engineering designers focus on shaping up the flow regime so that the greatest energy dissipation is ensured. On the other hand, the structural designers focus on load bearing capacity and durability of the structural components which may contradict the focus of the hydraulic experts. Such a case may occur when the spillway chute floor slab must be thin due to the limited spaces. Then, the dynamic load acting on the chute floor slab may compromise its long-term operation. The dynamic forces are created by the violent turbulences which may even coincide with the natural frequency of the reinforced concrete floor slab. Therefore, the objective of this paper is a complex approach to small-scale physical model testing which makes use of the latest rapid-prototyping techniques and the particle image velocimetry, and which in the end allows to estimate the magnitude of the dynamic hydraulic forces acting on the channel bed. The newly developed organic-shape energy dissipators play a key role in reducing the kinetic energy of water through its enhances aeration. The proposed method on a small scale can assist favorably the design process of real-scale hydraulic reinforced concrete structures.
水利工程设计师的工作重点是塑造水流状态,以确保最大程度地消散能量。另一方面,结构设计人员侧重于结构部件的承载能力和耐用性,这可能与水力专家的工作重点相矛盾。当溢流槽底板因空间有限而必须很薄时,就会出现这种情况。这时,作用在滑道底板上的动荷载可能会影响其长期运行。动荷载是由剧烈的湍流产生的,这些湍流甚至可能与钢筋混凝土楼板的固有频率相吻合。因此,本文的目标是利用最新的快速成型技术和粒子图像测速仪,采用复杂的方法进行小规模物理模型试验,最终估算出作用在滑道底板上的动态水力的大小。新开发的有机形状消能装置在通过增强曝气来降低水的动能方面发挥了关键作用。所提出的小规模方法可以为实际规模的水工钢筋混凝土结构的设计过程提供有益的帮助。
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引用次数: 0
Experimental Study of Vibration Isolation Using Electromagnetic Damping 利用电磁阻尼进行振动隔离的实验研究
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34759
Easu Dakshnamoorthy, Ralph H. Ryntathiang, Sarang, Sivakumar, Sidharth Krishna VINOD KUMAR
This study presents an experimental investigation focused on the reduction of vibrations using electromagnetic damping techniques. The objective is to explore the effectiveness of electromagnetic damping in mitigating undesirable vibrations and enhancing system stability. A single-degree vertically constrained spring-mass system, two pairs of electromagnets, Lab VIEW software, an accelerometer, DAQ card were used for the experimentation. SWG 17 and SWG19 coil electromagnets were used in different conditions of energization to evaluate the effectiveness of the electromagnetic damping system. The parameters such as excitation frequency, vibration amplitude, and electromagnetic damping force are systematically varied and their effects on vibration isolation are analysed. The results demonstrate that the electromagnetic damping system effectively isolates base induced vibrations across a range of frequencies and amplitudes. The experimental data reveal  that at lower frequencies, upto 6Hz the amplitude of RMS acceleration was same as that of the system without energizing the electromagnet and at higher frequencies, above 10 Hz, all 2V,4V and 6V of energized electromagnets in the SDVC system  showed negligible  variation in the  RMS amplitude of acceleration. A substantial isolation of top plate was observed at higher frequencies of base excitation.    
本研究介绍了一项实验调查,重点是利用电磁阻尼技术减少振动。目的是探索电磁阻尼在减轻不良振动和增强系统稳定性方面的有效性。实验使用了单度垂直约束弹簧-质量系统、两对电磁铁、Lab VIEW 软件、加速度计和 DAQ 卡。在不同的通电条件下使用了 SWG17 和 SWG19 线圈电磁铁,以评估电磁阻尼系统的有效性。系统地改变了激励频率、振幅和电磁阻尼力等参数,并分析了它们对隔振的影响。结果表明,电磁阻尼系统能在一定频率和振幅范围内有效地隔离基座引起的振动。实验数据显示,在较低频率(6 Hz 以下)下,加速度有效值振幅与未通电电磁铁的系统相同;在较高频率(10 Hz 以上)下,SDVC 系统中所有 2V、4V 和 6V 通电电磁铁的加速度有效值振幅变化微乎其微。在较高频率的底座激励下,顶板出现了明显的隔离现象。
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引用次数: 0
Vibration Characteristics Analysis of Twin-Screw Compressor Shell Based on the Fluid-Solid Coupling Method 基于流固耦合法的双螺杆压缩机壳体振动特性分析
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.33175
Yayin He, Wei Zhang, Xuyang He, Kai WANG, Junli Wang, Yongqiang Zhao
Under the action of the flow field force and the constraint reaction force of the negative rotor and the positive rotor, the twin screw compressor shell will produce vibration, which will affect the life of the parts and produce noise. The rotors restraint reaction force are calculated by fluid-structure coupling method. The shell inherent frequency is solved by modal analysis, and the shell resonance is analyzed during the rotors meshing process. On this basis, the flow field force and rotor constraint reaction force are used as the compressor shell vibration excitation sources, and the vibration response of the compressor shell under the action of excitation force is studied. The research results can provide some reference for the optimized design of compressor shell structure.
在流场力以及负转子和正转子的约束反力的作用下,双螺杆压缩机壳体会产生振动,从而影响部件的寿命并产生噪音。转子约束反力采用流固耦合法计算。通过模态分析求解壳体固有频率,分析转子啮合过程中的壳体共振。在此基础上,将流场力和转子约束反力作为压缩机壳体振动激振源,研究了激振力作用下压缩机壳体的振动响应。研究结果可为压缩机壳体结构的优化设计提供一定的参考。
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引用次数: 0
Study on the Thermal Sensitivity of Anisotropic Thin Sheets: Application to Hot Bulge Tests 各向异性薄板的热敏感性研究:热胀测试的应用
Pub Date : 2024-04-23 DOI: 10.5755/j02.mech.34214
Aboulbaba Eladeb, M. Nasri, Nidhal Becheikh, N. Ghazouani, M. Tashkandi
This article presents a study on the thermal sensitivity of anisotropic thin sheets, focusing specifically on their behavior during hot bulge tests. Anisotropic materials exhibit different mechanical properties in different directions, and understanding their response to thermal loading is crucial for various engineering applications. The experimental investigation involves subjecting thin sheets of anisotropic materials to controlled thermal conditions and measuring their response. The hot bulge test, a well-established method, is employed to analyze the behavior of the sheets under elevated temperatures. This test involves applying a controlled internal pressure to a heated circular and elliptical specimen, causing it to deform and form a bulge. Through this study, the thermal sensitivity of anisotropic thin sheets is characterized by analyzing the bulge height, bulge profile, and strain distribution. The influence of various factors, such as temperature, material anisotropy, and loading rate, is examined to understand their effects on the sheet's response. Experimental results reveal significant variations in the thermal sensitivity of anisotropic thin sheets, depending on the material's orientation and temperature. The study demonstrates that certain orientations exhibit greater sensitivity to thermal loading, leading to distinct bulge profiles and strain distributions. Furthermore, numerical simulations are conducted using finite element analysis to validate and complement the experimental findings. The simulation models incorporate the anisotropic material properties and the thermal boundary conditions, enabling a comprehensive understanding of the thermal sensitivity behavior observed experimentally. The outcomes of this study provide valuable insights into the thermal behavior of anisotropic thin sheets, particularly in the context of hot bulge tests. The findings contribute to the knowledge base of material characterization and can aid in the design and optimization of structures and components subjected to thermal loading, where anisotropic materials are involved.
本文介绍了对各向异性薄板热敏感性的研究,特别关注它们在热膨胀试验中的行为。各向异性材料在不同方向上表现出不同的机械特性,了解它们对热负荷的响应对各种工程应用至关重要。实验研究包括将各向异性材料薄片置于受控热条件下并测量其响应。热胀试验是一种成熟的方法,用于分析薄片在高温下的行为。该试验包括对加热的圆形和椭圆形试样施加受控内压,使其变形并形成隆起。这项研究通过分析隆起高度、隆起轮廓和应变分布,描述了各向异性薄板的热敏感性。研究了温度、材料各向异性和加载速率等各种因素的影响,以了解它们对薄片响应的影响。实验结果表明,各向异性薄片的热敏感性因材料的取向和温度而有很大不同。研究表明,某些取向对热负荷表现出更大的敏感性,从而导致不同的隆起轮廓和应变分布。此外,还利用有限元分析进行了数值模拟,以验证和补充实验结果。模拟模型结合了各向异性的材料特性和热边界条件,使人们能够全面了解实验观察到的热敏感性行为。这项研究的成果为了解各向异性薄片的热行为,尤其是热膨胀试验中的热行为,提供了宝贵的见解。研究结果有助于完善材料表征的知识库,并有助于设计和优化各向异性材料在热负荷作用下的结构和部件。
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引用次数: 0
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Mechanics
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