Acta Mechanica最新文献_第3页

Dynamic behavior of a class of predator–prey model with two time delays 一类具有两个时间延迟的捕食者--猎物模型的动态行为

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-10-01 DOI: 10.1007/s00707-024-04111-w

Youhua Qian, Meirong Ren, Haolan Wang

引用次数: 0

Revisiting visualization of spiral states in a wide-gap spherical Couette flow 重温宽间隙球形库埃特流中螺旋状态的可视化

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-10-01 DOI: 10.1007/s00707-024-04098-4

Isshin Arai, Tomoaki Itano, Masako Sugihara-Seki

{"title":"Revisiting visualization of spiral states in a wide-gap spherical Couette flow","authors":"Isshin Arai, Tomoaki Itano, Masako Sugihara-Seki","doi":"10.1007/s00707-024-04098-4","DOIUrl":"10.1007/s00707-024-04098-4","url":null,"abstract":"<div><p>A pioneering study conducted by Egbers and Rath [Acta Mech. 111 pp. 125–140 (1995)] experimentally captured spiral waves to elucidate the transition in the wide-gap spherical Couette flow. However, the physical field quantities of the spiral waves corresponding to light patterns of various intensities, as obtained in the experiment, remain unclear, and we have yet to move beyond the understanding that the reflected light from shear-sensitive flake tracers responds to a flow that appears at the transition. In this study, the experiment to visualize spiral waves using aluminum flakes, as performed by Egbers and Rath, was numerically reproduced by solving the translational and rotational motions of the particles in a spiral wave. First, the spiral wave in a spherical Couette flow with an aspect ratio <span>(eta =1/2)</span> was numerically calculated using the Newton–Raphson method. Subsequently, the image that was numerically reproduced from the spiral wave was compared with an experimentally visualized image. The torque acting on the inner sphere and the phase angular velocity of the spiral waves with various wavenumbers were provided. Attempts have been made to determine the instantaneous physical quantity that corresponds to the light and dark patterns observed in the flow visualization. From the attempts, we concluded the orientation motion of the flakes developed in the advective history of the flow is essential to yield these patterns. Exploring the correlation between flow visualization results and shear structures may provide a new avenue for quantitatively estimating spatial structures and time scales in complex and quickly time-varying flow fields, such as turbulence.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7441 - 7452"},"PeriodicalIF":2.3,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Local–nonlocal integral theories of elasticity with discontinuity for longitudinal vibration analysis of cracked rods 用于裂杆纵向振动分析的不连续弹性局部-非局部积分理论

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-30 DOI: 10.1007/s00707-024-04105-8

Pei Zhang, Peter Schiavone, Hai Qing

{"title":"Local–nonlocal integral theories of elasticity with discontinuity for longitudinal vibration analysis of cracked rods","authors":"Pei Zhang, Peter Schiavone, Hai Qing","doi":"10.1007/s00707-024-04105-8","DOIUrl":"10.1007/s00707-024-04105-8","url":null,"abstract":"<div><p>We present a size-dependent formulation for the longitudinal vibration study of cracked thick rods based on both the strain and stress-driven local/nonlocal mixture theories of elasticity with discontinuity. Due to the presence of the crack, the rod is divided into two segments connected by a linear spring, and compatibility conditions are given to describe the geometric discontinuity caused by the crack. The equations of motion of the discrete rods are formulated based on Rayleigh rod theory, and the two classes of local–nonlocal constitutive equations are integrated into an equivalent differential form, equipped with a set of constitutive boundary conditions at two ends of the whole structure and a set of constitutive continuity conditions at the junction of the sub-structures. The differential quadrature method (GDQM), together with the interpolation quadrature formula, is introduced to solve all the equations of motion of the sub-rods, the above constraint condition and the definite integrals occurring therein, simultaneously, through which we extract the dimensionless frequencies of the cracked rods with different boundary edges. After conducting comparison studies with the existing literature, numerical studies reveal that the present local–nonlocal model with discontinuity can effectively address the softening (or hardening) phenomenon as the structure’s size reduces. Moreover, the influence of crack location, crack severity, inertia of lateral motions and nonlocal parameters on the rods’ vibration frequencies is examined in detail.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7419 - 7440"},"PeriodicalIF":2.3,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dispersion and bandgap feature of coupled Bloch waves in one-dimensional piezoelectric semiconductor phononic crystal with PN junction 带 PN 结的一维压电半导体声子晶体中耦合布洛赫波的色散和带隙特征

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-30 DOI: 10.1007/s00707-024-04094-8

Zibo Wei, Peijun Wei, Chunyu Xu, Xiao Guo

{"title":"Dispersion and bandgap feature of coupled Bloch waves in one-dimensional piezoelectric semiconductor phononic crystal with PN junction","authors":"Zibo Wei, Peijun Wei, Chunyu Xu, Xiao Guo","doi":"10.1007/s00707-024-04094-8","DOIUrl":"10.1007/s00707-024-04094-8","url":null,"abstract":"<div><p>The dispersion, attenuation and bandgap feature of coupled Bloch waves in one-dimensional piezoelectric semiconductor phononic crystal are studied in the present work. In particular, the influences of PN junction are emphasized. Different from the Bloch waves in the piezoelectric phononic crystal, the Bloch wave in piezoelectric semiconductor phononic crystal is attenuated. Moreover, the existence of the carrier fields brings forth more modes of Bloch waves due to the coupling of multiple physical fields. Using the state transfer equation method, the transfer matrix of the unit cell in a one-dimensional piezoelectric semiconductor phononic crystal is derived. Combining this with Bloch theory for periodic structures, the dispersion equation for multi-field coupled Bloch waves is obtained. The dispersion, attenuation and bandgap characteristics of the coupled Bloch waves are then plotted in the complex wave number domain. It is found that the influences of the PN junction are evident and thus provide an enlightenment that the propagation feature of Bloch waves can be adjusted by the control of the PN junction.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7405 - 7417"},"PeriodicalIF":2.3,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Lamb waves in sandwich plates: group velocity not equal to velocity of energy transport 夹层板中的 Lamb 波：群速度不等于能量传输速度

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-29 DOI: 10.1007/s00707-024-04099-3

Sergey V. Kuznetsov

引用次数: 0

Numerical study of steam flow on the low-pressure turbine under off-design conditions: a case study of the Neka steam power plant 非设计条件下低压涡轮机上蒸汽流的数值研究：Neka 蒸汽发电厂案例研究

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-29 DOI: 10.1007/s00707-024-04097-5

Jamshid Naeimi, Saadat Zirak, Mojtaba Biglari, Iraj Jafari Gavzan

{"title":"Numerical study of steam flow on the low-pressure turbine under off-design conditions: a case study of the Neka steam power plant","authors":"Jamshid Naeimi, Saadat Zirak, Mojtaba Biglari, Iraj Jafari Gavzan","doi":"10.1007/s00707-024-04097-5","DOIUrl":"10.1007/s00707-024-04097-5","url":null,"abstract":"<div><p>In the repowering of conventional steam power plants, we face off-design conditions. In this paper, a numerical study of the steam flow in the blades of the last stage of the low-pressure turbine of the Neka thermal power plant was carried out. To analyze the steam flow in the turbine, one design mode and two off-design modes including part-load and over-load were considered. In this research, three-dimensional Reynolds-averaged Navier–Stokes equations were simulated by using Ansys CFX software. Also, the SST k-ω method was used to model the turbulent flow. According to the obtained results, the effect of steam mass flow rate changes on the low-pressure turbine performance, such as velocity triangles, pressure, Mach number, and temperature distribution on blade surfaces, flow angles, degree of reaction, back pressure, steam quality, and efficiency, was investigated. For example, the loss of isentropic efficiency of the last stage in the off-design mode was less than 0.37% compared to the design conditions. Furthermore, the changes in the degree of reaction of the blades due to the changes in the mass flow rate of the fluid were less than 3%. Validation of the numerical solution was done in two-dimensional and three-dimensional models, and the results showed that there was a good agreement between numerical simulation and experimental data.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7369 - 7391"},"PeriodicalIF":2.3,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An improved incompressible SPH with unified semi-analytical wall boundary conditions for free surface flow 采用统一半解析壁面边界条件的改进型不可压缩自由表面流 SPH

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-28 DOI: 10.1007/s00707-024-04103-w

Jianwu Ruan, Lihua Wang, Yueting Zhou

{"title":"An improved incompressible SPH with unified semi-analytical wall boundary conditions for free surface flow","authors":"Jianwu Ruan, Lihua Wang, Yueting Zhou","doi":"10.1007/s00707-024-04103-w","DOIUrl":"10.1007/s00707-024-04103-w","url":null,"abstract":"<div><p>An enhanced treatment of the free surface boundary in the incompressible smoothed particle hydrodynamics (ISPH) method using the unified semi-analytical wall (USAW) boundary is proposed in this work. The instability problem at the free surface caused by kernel truncation can be resolved by assuming some virtual particles around the surface. The pressure of the virtual particles is considered as zero to impose pressure boundary conditions on the free surface, while the pressure of free surface particles is set to be a tiny value to reduce particle accumulation. To further improve the stability, the non-penetration algorithm is employed on the USAW boundary to avoid particle penetration. Afterward, the ISPH method with the USAW boundary is utilized to simulate several free surface flow problems. The enhancement of stability as well as the accuracy of the simulations is validated firstly by the dam break tests and further studied through examples of solitary wave propagation and liquid sloshing. The numerical results are compared with available experiment data or results from other numerical methods, verifying that the improved ISPH model with the USAW boundary in this work is highly suitable for simulating free surface flow problems.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7351 - 7368"},"PeriodicalIF":2.3,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142737102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study of biaxial stress transfer in multilayer composites under uniaxial or biaxial tensile loading 单轴或双轴拉伸加载下多层复合材料的双轴应力传递研究

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-27 DOI: 10.1007/s00707-024-04100-z

Si-Yu Guo, Hui-Ying Zhang, Yan-Gao Hu

引用次数: 0

Multifield gradient theory on vibration of FG magneto-electro-elastic microbeams resting on Pasternak foundation 帕斯捷尔纳克地基上 FG 磁弹性微梁振动的多场梯度理论

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-27 DOI: 10.1007/s00707-024-04066-y

Y. S. Li, S. Li

引用次数: 0

Predictive modeling of nonlinear system responses using the Residual Improvement Deep Learning Algorithm (RIDLA) 利用残差改进深度学习算法（RIDLA）对非线性系统响应进行预测建模

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-09-27 DOI: 10.1007/s00707-024-04095-7

Naijian Gu, Wenhua Wu, Kun Liu, Xinglin Guo

{"title":"Predictive modeling of nonlinear system responses using the Residual Improvement Deep Learning Algorithm (RIDLA)","authors":"Naijian Gu, Wenhua Wu, Kun Liu, Xinglin Guo","doi":"10.1007/s00707-024-04095-7","DOIUrl":"10.1007/s00707-024-04095-7","url":null,"abstract":"<div><p>Predicting specific location responses in nonlinear systems under random excitations is crucial for structural health monitoring, optimization design, and safety assessment. Traditional sensor-based response measurements face challenges due to limitations in quantity and installation positions, while nonlinear time history analysis suffers from high computational costs and modeling time. Simplified regression equations used in engineering often lack accuracy. This study introduces a novel Residual Improvement Deep Learning Algorithm (RIDLA) to construct high-precision prediction models for nonlinear systems subjected to random excitations. RIDLA leverages Long Short-Term Memory (LSTM) neural networks to capture nonlinear relationships in time series and iteratively improve model accuracy through interactive training with measured responses and computed residuals. This approach effectively predicts time history responses of nonlinear systems under random excitations. RIDLA’s performance is validated by predicting responses in two typical nonlinear systems: a 6-DOF nonlinear oscillator system and the interface force of a satellite–rocket connection subjected to random excitations. The results demonstrate that RIDLA provides highly accurate predictions and can be applied to other complex nonlinear systems.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 12","pages":"7301 - 7315"},"PeriodicalIF":2.3,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0