Acta Mechanica最新文献_第10页

Flow characteristics at the interface during droplet formation in a flow-focusing microfluidic channel—numerical analysis of dripping and jetting regimes 流动聚焦微流体通道中液滴形成过程中界面的流动特性--对滴落和喷射状态的数值分析

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-26 DOI: 10.1007/s00707-024-04031-9

Emil Grigorov, Jordan A. Denev, Boris Kirov, Vassil Galabov

{"title":"Flow characteristics at the interface during droplet formation in a flow-focusing microfluidic channel—numerical analysis of dripping and jetting regimes","authors":"Emil Grigorov, Jordan A. Denev, Boris Kirov, Vassil Galabov","doi":"10.1007/s00707-024-04031-9","DOIUrl":"10.1007/s00707-024-04031-9","url":null,"abstract":"<div><p>This work has the purpose to elucidate in deeper detail the conjugated physical phenomena at the interface between two immiscible fluids in microfluidic devices. The two typical regimes—dripping and jetting—emerging in flow-focusing devices are considered for the analysis. Dynamic (time-dependent analysis of fixed or Lagrangian-tracked points) and local (lines along the interface, at a fixed time instance) analyses have been conducted from a parallel numerical simulation on a fine numerical grid. The results comprise various pressures and tangential stresses and their balance during the droplet formation process with special attention paid to the moments and locations of the droplet release. It was found that the dripping regime is characterized by the local balance of the pressure drop due to surface tension <span>({ {Delta p}}_{upsigma } text{and})</span> the Laplace pressure <span>({ {Delta p}}_{text{Lapl}})</span> across the interface. Only at the last moments before the droplet pinch-off does the former pressure dominate. In contrast, in the jetting regime, there is a clear domination of the pressure due to tension during the whole process of droplet formation. Shear stresses, presented by the von Mises criterion, are several times (jetting regime) or even an order of magnitude (dripping regime) lower than the surface tension pressure and the Laplace pressure. In both regimes, when the interface curvature κ changes locally its sign, the pressure at the centerline axis shows a clear local maximum. For the jetting regime, the downstream derivative of this centerline pressure is the first parameter that changes along the jet axis—thus indicating the onset of instabilities for this regime—and it is then followed by a wavelike change of the radius of the jet.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"6057 - 6075"},"PeriodicalIF":2.3,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782054","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

CFD-DEM modelling of particle entrainment in wheel–rail interface: a parametric study on train characteristics 轮轨界面颗粒夹带的 CFD-DEM 建模：关于列车特性的参数研究

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-26 DOI: 10.1007/s00707-024-04032-8

Sadaf Maramizonouz, Sadegh Nadimi, Roger Lewis

{"title":"CFD-DEM modelling of particle entrainment in wheel–rail interface: a parametric study on train characteristics","authors":"Sadaf Maramizonouz, Sadegh Nadimi, Roger Lewis","doi":"10.1007/s00707-024-04032-8","DOIUrl":"10.1007/s00707-024-04032-8","url":null,"abstract":"<div><p>Rail-sanding is employed to improve the train’s wheel–rail traction loss in low adhesion conditions. This can significantly impede trains’ kinematics, operation, and performance by hindering the train’s acceleration and deceleration, resulting in delays and unreliability of transport system as well as causing safety risks and in the worst cases train collisions. Rail-sanding has its own merits in recovering the wheel–rail traction but can result in a sand wastage of more than 80% due to its low sand entrainment efficiency. In this research, computational fluid dynamics is coupled to discrete element modelling to study the behaviour of sand particles during rail-sanding. A parametric study based on the train characteristics, including train velocity, sand flow rate, and the geometry of the sander nozzle, is performed by comparing the entrainment efficiency of the sand particles. It is found that train velocities over 30 m/s result in the entrainment efficiency of almost zero. A moving air layer generated at the wheel–rail interface influences the lower bound of acceptable particle size range. The flow rate and nozzle geometry can be designed to enhance entrainment efficiency.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"6077 - 6087"},"PeriodicalIF":2.3,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00707-024-04032-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Vibration stability and bifurcation analysis of two-stage spur gear systems supported by squeeze film dampers 由挤压膜阻尼器支撑的双级正齿轮系统的振动稳定性和分岔分析

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-24 DOI: 10.1007/s00707-024-04021-x

Hongtai Shi, Weitao Chen, Jingbin Li, Zhipeng Wang, Long Jiang

{"title":"Vibration stability and bifurcation analysis of two-stage spur gear systems supported by squeeze film dampers","authors":"Hongtai Shi, Weitao Chen, Jingbin Li, Zhipeng Wang, Long Jiang","doi":"10.1007/s00707-024-04021-x","DOIUrl":"10.1007/s00707-024-04021-x","url":null,"abstract":"<div><p>The squeeze film dampers (SFDs) demonstrate superior efficacy in attenuating vibrations. In the present study, the oil-film forces of SFDs are computed utilizing the finite element method, adhering to the Galerkin principle. Taking into account the time-varying meshing stiffness (TVMS), static transmission error (STE), and tooth backlash, a nonlinear dynamic model for a two-stage spur gear system, bolstered by SFDs, is developed by the lumped parameter methodology and D’Alembert’s principle. Based on the Gram-Schmidt QR decomposition, a strategy for calculating the Lyapunov exponent spectrum and Floquet characteristic multipliers of high-dimensional gear-rotor-SFD systems is proposed. By comparing with classical literature, the accuracy of the computational strategy is verified. Qualitative and quantitative assessments are conducted on the vibration stability of a two-stage spur gear system supported by rolling bearings and SFDs. The analysis evaluated the damping effect of SFDs in enhancing the vibration stability of gear systems and improving the periodic motion of the system. The study indicates that the application of SFDs can effectively reduce the occurrence of saddle-node bifurcations, Hopf bifurcations, and period-doubling bifurcations, and the chaotic and unstable vibration region is greatly narrowed and suppress nonlinear characteristics such as bistable responses and jump phenomena.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"6011 - 6032"},"PeriodicalIF":2.3,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782159","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

Prestressed vibration and buckling analysis of graphene platelets reinforced composite plates using the dynamic stiffness method 使用动态刚度法对石墨烯平板增强复合板进行预应力振动和屈曲分析

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-23 DOI: 10.1007/s00707-024-04016-8

Raj Kumar, Prasun Jana

{"title":"Prestressed vibration and buckling analysis of graphene platelets reinforced composite plates using the dynamic stiffness method","authors":"Raj Kumar, Prasun Jana","doi":"10.1007/s00707-024-04016-8","DOIUrl":"10.1007/s00707-024-04016-8","url":null,"abstract":"<div><p>The article presents the use of the dynamic stiffness method (DSM) for analyzing the buckling and prestressed vibration of advanced composite plates subjected to uniaxial and biaxial in-plane loads. The plate consists of laminated layers reinforced with graphene platelets and the effective material properties of the plate are computed using the Halpin-Tsai micromechanical model. Through the application of Hamilton’s principle, the governing differential equations (GDEs), based on the first order shear deformation theory, are obtained for the GPL-reinforced plate resting on elastic foundations. For a segment of the plate, the dynamic stiffness matrix is obtained by solving the GDEs with the Levy form of boundary conditions. Subsequently, the assembled global dynamic stiffness matrix is solved using the Wittrick-Williams algorithm to compute the buckling and prestressed vibration behavior of the plates. Convergence and comparative studies are performed to show that the DSM is efficient and produces very accurate results as it is formulated based on closed-form solutions. Several parametric studies are carried out to study the effect of different edge loads, foundation parameters, and plate boundary conditions. Results for non-uniform plate configurations are also presented to highlight the applicability and efficacy of the present DSM to fairly complex plate configurations.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"5963 - 5992"},"PeriodicalIF":2.3,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782088","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

A novel efficient energy absorber: circular metal foam-filled tube under external inversion over a die 新型高效能量吸收器：模具外部反转下的圆形金属泡沫填充管

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-23 DOI: 10.1007/s00707-024-04030-w

Jinwen Bai, Jianxun Zhang

{"title":"A novel efficient energy absorber: circular metal foam-filled tube under external inversion over a die","authors":"Jinwen Bai, Jianxun Zhang","doi":"10.1007/s00707-024-04030-w","DOIUrl":"10.1007/s00707-024-04030-w","url":null,"abstract":"<div><p>To enhance the energy-absorbing capacity of the energy absorber, the circular metal foam-filled tube (CMFFT) under external inversion over a circular die is designed. According to the rule of energy conservation, a theoretical model for the inversion of the CMFFT over a circular die is proposed, considering the radial bending of the CMFFT and the circumferential expansion of the CMFFT in the contact region and disengaging region, and the foam compression. Then, the die inversion deformation of the CMFFT under axial compression is investigated by the commercial software ABAQUS/Explicit. It is seen that the analytical model captures the numerical results reasonably. Next, the influences of the strength of the metal filled foam, the circular corner radius of the die, the average radius of the metal circular tube and the wall thickness of the metal circular tube are discussed. It is found that the force increases with the strength of the metal filled foam and the average radius of the metal circular tube. In addition, the force firstly decreases and then increases with the increase of the radius of the circular die and the wall thickness of the metal circular tube. The absorbed energy increases with the wall thickness of the metal circular tube, the circular corner radius of the die, the average radius of the metal circular tube, and the strength of the metal filled foam. The optimum radius of the circular die is proposed based on the theoretical model. The special energy absorption (SEA) efficiency of the CMFFT under external inversion over a circular die is significantly better than the metal empty tube. The SEA ratio of the CMFFT is 130.21%, when the compressive strength of metal filled foam <span>(overline{sigma }_{F} = 0.0{694})</span>. It is demonstrated that the CMFFT under external inversion over a die is a good energy absorber.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"5993 - 6010"},"PeriodicalIF":2.3,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782057","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

Analysis of effects of inlet air and fuel conditions on reactive flow characteristics in a gas turbine model combustion chamber 分析进气和燃料条件对燃气轮机模型燃烧室内反应流特性的影响

IF 2.7 3区工程技术

Acta Mechanica Pub Date : 2024-07-22 DOI: 10.1007/s00707-024-04023-9

Mohammad Sadegh Abedinejad, Farzad Bazdidi-Tehrani, Ebrahim Sharifi-Sedeh

{"title":"Analysis of effects of inlet air and fuel conditions on reactive flow characteristics in a gas turbine model combustion chamber","authors":"Mohammad Sadegh Abedinejad, Farzad Bazdidi-Tehrani, Ebrahim Sharifi-Sedeh","doi":"10.1007/s00707-024-04023-9","DOIUrl":"https://doi.org/10.1007/s00707-024-04023-9","url":null,"abstract":"<p>The aim of the current article is to study the combustion characteristics of the liquid fuel (Jet-A) inside a gas turbine model combustor under different conditions of the inlet air and fuel. The two-phase flow of the air and liquid droplets is modeled with the two-way coupling in the Eulerian–Lagrangian approach. The steady flamelet and discrete ordinates models are implemented to model the combustion and radiative heat transfer, successively. The <span>({text{NO}}_{text{x}})</span> modeling is done as a post-process using the finite rate model. The outcomes indicate that increasing the fuel spray velocity leads to an improvement in the combustion phenomenon in the primary region, a rise in the flame temperature, and finally, a growth in the amount of <span>({text{NO}}_{text{x}})</span> produced. By decreasing the half angle of fuel injection by 10°, the maximum temperature inside the combustion chamber decreases by 43 K. An increase of <span>(26text{%})</span> in the inlet air temperature (from <span>(373)</span> to <span>(473text{ K})</span>) does not have a considerable effect on the species’ concentration distribution. However, with a <span>(54text{%})</span> growth in the inlet air temperature, changes in the concentration distributions particularly in the concentration of <span>({text{CO}}_{2})</span> become noticeable. Enhancing the temperature of the inlet air causes a rise in the concentration of <span>(text{NO})</span>. The concentration of <span>(text{NO})</span> is highly dependent on the inlet air pressure, and a direct relationship has been observed between increasing the inlet air pressure and the amount of the <span>(text{NO})</span> produced.</p>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"21 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782056","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

Enhancing non-intrusive reduced-order models with space-dependent aggregation methods 用空间相关聚合方法增强非侵入式降阶模型

IF 2.7 3区工程技术

Acta Mechanica Pub Date : 2024-07-22 DOI: 10.1007/s00707-024-04007-9

Anna Ivagnes, Niccolò Tonicello, Paola Cinnella, Gianluigi Rozza

{"title":"Enhancing non-intrusive reduced-order models with space-dependent aggregation methods","authors":"Anna Ivagnes, Niccolò Tonicello, Paola Cinnella, Gianluigi Rozza","doi":"10.1007/s00707-024-04007-9","DOIUrl":"https://doi.org/10.1007/s00707-024-04007-9","url":null,"abstract":"<p>In this manuscript, we combine non-intrusive reduced-order models (ROMs) with space-dependent aggregation techniques to build a <i>mixed-ROM</i>, able to accurately capture the flow dynamics in different physical settings. The flow prediction obtained using the <i>mixed</i> formulation is derived from a convex combination of the predictions of several previously trained reduced-order models (ROMs), with each model assigned a space-dependent weight. The ROMs incorporated in the <i>mixed</i> model utilize different <i>reduction</i> methods, such as proper orthogonal decomposition and autoencoders, and various <i>approximation</i> techniques, including radial basis function interpolation (RBF), Gaussian process regression, and feed-forward artificial neural networks. Each model’s contribution is given higher weights in regions where it performs best and lower weights where its accuracy is lower compared to the other models. Additionally, a random forest regression technique is used to determine the weights for previously unseen conditions. The performance of the aggregated model is assessed through two test cases: the 2D flow past a NACA 4412 airfoil at a 5-degree angle of attack, with the Reynolds number ranging between <span>(1 times 10^{5})</span> and <span>(1 times 10^{6})</span>, and a transonic flow over a NACA 0012 airfoil, with the angle of attack as the varying parameter. In both scenarios, the mixed-ROM demonstrated improved accuracy compared to each individual ROM technique, while providing an estimate for the predictive uncertainty.</p>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"4 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785840","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

Reflection and transmission of plane waves at interface between two transversely isotropic microstretch half-spaces 平面波在两个横向各向同性微拉伸半空间界面上的反射和传输

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-20 DOI: 10.1007/s00707-024-04013-x

Princy Gupta, Jitander Singh Sikka

引用次数: 0

A novel metamaterial multiple beam structure with internal local resonance 具有内部局部共振的新型超材料多波束结构

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-20 DOI: 10.1007/s00707-024-04006-w

Giuseppe Failla, Andrea Burlon, Andrea Francesco Russillo

{"title":"A novel metamaterial multiple beam structure with internal local resonance","authors":"Giuseppe Failla, Andrea Burlon, Andrea Francesco Russillo","doi":"10.1007/s00707-024-04006-w","DOIUrl":"10.1007/s00707-024-04006-w","url":null,"abstract":"<div><p>This paper presents a novel locally resonant metamaterial structure and proposes a method to analyze its elastic wave dispersion properties. The structure is conceived as a multiple beam system with parallel beams transversely interconnected by periodic arrays of small resonators, each consisting of a spring-mass-spring subsystem in parallel with a couple of springs. Inserting the resonators between the beams, instead of attaching them as external appendages like in some alternative examples of locally resonant beams in the literature, makes the structure appealing for practical realization and use; furthermore, hosting several arrays of resonators gives the possibility to open multiple band gaps. The proposed method is a homogenization approach for flexural wave dispersion analysis, which removes the equations for the resonators from the set governing the dynamics of the system and reverts the original structure to an equivalent one featuring a tri-diagonal effective mass matrix with frequency dependent terms. The advantage of the homogenization approach is twofold: (1) it demonstrates that the band gaps arise in the frequency ranges where the effective mass matrix is negative definite, generalizing the well-established concept of band gaps attributable to negative mass effects in single locally resonant beams; (2) it provides dispersion curves and band gaps very efficiently, and the band gaps are identified upon calculating the eigenvalues of the tri-diagonal effective mass matrix. Analytical expressions of the band gap edges are obtained for the baseline case of a double beam system, to be readily used for design. Additionally, the exact transfer matrix method in conjunction with the Bloch theorem is formulated as alternative to the homogenization approach for wave dispersion analysis. Finally, the proposed concept of locally resonant structure and pertinent homogenization approach are validated by calculating the transmittance properties of the corresponding finite structure, via the standard finite element method.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 9","pages":"5885 - 5903"},"PeriodicalIF":2.3,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742217","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

A dislocation-based crystal plasticity model for single-crystal micropillars based on strain burst with stochastic characteristics 基于随机应变爆发的单晶微柱的位错晶体塑性模型

IF 2.3 3区工程技术

Acta Mechanica Pub Date : 2024-07-20 DOI: 10.1007/s00707-024-04022-w

Huili Guo, Wenjie Xu, Fulin Shang

{"title":"A dislocation-based crystal plasticity model for single-crystal micropillars based on strain burst with stochastic characteristics","authors":"Huili Guo, Wenjie Xu, Fulin Shang","doi":"10.1007/s00707-024-04022-w","DOIUrl":"10.1007/s00707-024-04022-w","url":null,"abstract":"<div><p>The recent uniaxial micron-compression experiments exhibit the size effect and stochastic phenomenon such as stair-like fluctuation of the strain for the plasticity deformation of the single-crystal micropillars. Nevertheless, the current crystal plasticity theories fail to predict and characterize these phenomena due to lack of consideration of the related physical mechanisms. To compensate for such deficiency, this paper mainly aims to establish a dislocation-based crystal plasticity model for the single-crystal micropillars in the micro-compression to characterize the jerky fluctuation features by considering variational and stochastic micro-boundary conditions, which are controlled the dislocation source length. The new model is applied to investigate the size effect and stair-like fluctuation of the strain for single-crystal Ni with size from 2 to 20 μm by the finite element analysis. The predicted intermittent flows match well with those by experimental observations during the plastic flow. The simulation results reveal that the stress and the amplitude of the strain burst show obvious size effect and stochastic behavior.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"235 10","pages":"5947 - 5962"},"PeriodicalIF":2.3,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742218","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