{"title":"Effect of leading-edge tubercles on the flow over low-aspect-ratio wings at low Reynolds number","authors":"Pengxin Yang, Yichen Zhu, Jinjun Wang","doi":"10.1016/j.taml.2022.100386","DOIUrl":"10.1016/j.taml.2022.100386","url":null,"abstract":"<div><p>Two-dimensional time-resolved particle image velocimetry (TR-PIV) and stereographic particle image velocimetry (SPIV) techniques were used to investigate the effect of leading-edge tubercles on the flow over low-aspect-ratio wing models. The angle of attack is fixed at 10°, and the Reynolds number based on chord length is 5.8 × 10<sup>3</sup>. It is shown that the leading-edge tubercles can effectively mitigate flow separation in the model and also reduce the contribution of wake vortex to the fluctuating energy of flow. Counter-rotating vortex pairs (CVPs) initiated from the peak of leading-edge tubercles can promote nearby momentum exchange, enhance mixing of the flow and increase the energy contained in the boundary layer, which results in resisting the larger adverse pressure gradient. Therefore, it is concluded that CVPs play an important role in mitigating the flow separation for wings with leading-edge tubercles.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"13 1","pages":"Article 100386"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47577878","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}
{"title":"Artificial neural network-based subgrid-scale models for LES of compressible turbulent channel flow","authors":"Qingjia Meng , Zhou Jiang , Jianchun Wang","doi":"10.1016/j.taml.2022.100399","DOIUrl":"10.1016/j.taml.2022.100399","url":null,"abstract":"<div><p>Fully connected neural networks (FCNNs) have been developed for the closure of subgrid-scale (SGS) stress and SGS heat flux in large-eddy simulations of compressible turbulent channel flow. The FCNN-based SGS model trained using data with Mach number <span><math><mrow><mi>M</mi><mi>a</mi><mo>=</mo><mn>3.0</mn></mrow></math></span> and Reynolds number <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>3000</mn></mrow></math></span> was applied to situations with different Mach numbers and Reynolds numbers. The input variables of the neural network model were the filtered velocity gradients and temperature gradients at a single spatial grid point. The <em>a priori</em> test showed that the FCNN model had a correlation coefficient larger than 0.91 and a relative error smaller than 0.43, with much better reconstructions of SGS unclosed terms than the dynamic Smagorinsky model (DSM). In <em>a posteriori</em> test, the behavior of the FCNN model was marginally better than that of the DSM in predicting the mean velocity profiles, mean temperature profiles, turbulent intensities, total Reynolds stress, total Reynolds heat flux, and mean SGS flux of kinetic energy, and outperformed the Smagorinsky model.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"13 1","pages":"Article 100399"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42455273","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}
{"title":"Artificial neural network-based one-equation model for simulation of laminar-turbulent transitional flow","authors":"Lei Wu , Bing Cui , Zuoli Xiao","doi":"10.1016/j.taml.2022.100387","DOIUrl":"https://doi.org/10.1016/j.taml.2022.100387","url":null,"abstract":"<div><p>A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network (ANN), which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras (SA)-<span><math><mi>γ</mi></math></span> model. By taking SA-<span><math><mi>γ</mi></math></span> model as the benchmark, the present ANN model is trained at two airfoils with various angles of attack, Mach numbers and Reynolds numbers, and tested with unseen airfoils in different flow states. The <em>a posteriori</em> tests manifest that the mean pressure coefficient, skin friction coefficient, size of laminar separation bubble, mean streamwise velocity, Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-<span><math><mi>γ</mi></math></span> model. Furthermore, the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-<span><math><mi>γ</mi></math></span> model.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"13 1","pages":"Article 100387"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49709032","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}
{"title":"New algorithm of shape-finding of suspension bridge with spatial cables","authors":"Xiao-Kang Deng , Zhuo Deng , Xin Ren","doi":"10.1016/j.taml.2022.100402","DOIUrl":"10.1016/j.taml.2022.100402","url":null,"abstract":"<div><p>A new algorithm is proposed to solve the problems of shape-finding of suspension bridge with spatial cables what include tedious iteration, slow convergence speed and even no convergent under some circumstances. In this paper, the stress analysis of the main cable is carried out, and the relationship between the slope change and the coordinate change is found. This paper also discussed how to find the minimum slope point of symmetrical or asymmetric main cable, and the deformation compatibility equation is established and solved to obtain the shape of main cable. The algorithm in this paper can ensure the convergence of the solution for the suspension bridge with spatial cables. The calculation accuracy is high through the demonstration of the calculation examples.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"13 1","pages":"Article 100402"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45617544","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}
Zi-Fei Lin , Yan-Ming Liang , Jia-Li Zhao , Jiao-Rui Li
{"title":"Predicting solutions of the Lotka‐Volterra equation using hybrid deep network","authors":"Zi-Fei Lin , Yan-Ming Liang , Jia-Li Zhao , Jiao-Rui Li","doi":"10.1016/j.taml.2022.100384","DOIUrl":"10.1016/j.taml.2022.100384","url":null,"abstract":"<div><p>Prediction of Lotka-Volterra equations has always been a complex problem due to their dynamic properties. In this paper, we present an algorithm for predicting the Lotka-Volterra equation and investigate the prediction for both the original system and the system driven by noise. This demonstrates that deep learning can be applied in dynamics of population. This is the first study that uses deep learning algorithms to predict Lotka-Volterra equations. Several numerical examples are presented to illustrate the performances of the proposed algorithm, including Predator nonlinear breeding and prey competition systems, one prey and two predator competition systems, and their respective systems. All the results suggest that the proposed algorithm is feasible and effective for predicting Lotka-Volterra equations. Furthermore, the influence of the optimizer on the algorithm is discussed in detail. These results indicate that the performance of the machine learning technique can be improved by constructing the neural networks appropriately.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100384"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000642/pdfft?md5=206b18bf31ec90ab00a5aa32543d0d0b&pid=1-s2.0-S2095034922000642-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41553026","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}
{"title":"Influence of physical parameters on the collapse of a spherical bubble","authors":"Bo-Hua Sun","doi":"10.1016/j.taml.2022.100369","DOIUrl":"https://doi.org/10.1016/j.taml.2022.100369","url":null,"abstract":"<div><p>This paper examines the influence of physical parameters on the collapse dynamics of a spherical bubble filled with diatomic gas (<span><math><mrow><mi>κ</mi><mo>=</mo><mn>7</mn><mo>/</mo><mn>5</mn></mrow></math></span>). The problem is formulated by the Rayleigh–Plesset dynamical equation, whose numerical solutions are carried out by Maple. Our studies show that each physical parameter affects the bubble collapse dynamics in different degree, which reveals that bubble collapse dynamics must considers all the parameters including liquid viscosity, surface tension, etc, else the outcome cannot be trusted.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100369"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000496/pdfft?md5=26f834976e3bf0976ce842c74e65613b&pid=1-s2.0-S2095034922000496-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"137328557","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}
{"title":"Sedimentation motion of sand particles in moving water (I): The resistance on a small sphere moving in non-uniform flow","authors":"Shu-Tang Tsai","doi":"10.1016/j.taml.2022.100392","DOIUrl":"10.1016/j.taml.2022.100392","url":null,"abstract":"<div><p>In hydraulics, when we deal with the problem of sand particles moving relative to the surrounding water, Stokes’ formula of resistance has usually been used to render the velocity of sedimentation of the particles. But such an approach has not been proved rigorously, and its accuracy must be carefully considered. In this paper, we discuss the problem of a sphere moving in a non-uniform flow field, on the basis of the fundamental theory of hydrodynamics. We introduce two assumptions: i) the diameter of the sphere is much smaller than the linear dimension of the flow field, and ii) the velocity of the sphere relative to the surrounding water is very small. Using these two assumptions, we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform, and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100392"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000721/pdfft?md5=20caceabd265b693c87cd2fd28f86ae1&pid=1-s2.0-S2095034922000721-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41817752","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}
{"title":"Numerical simulation of laser ultrasonic detection of the surface microdefects on laser powder bed fusion additive manufactured 316L stainless steel","authors":"Yang Liu , Zhixin Peng , Sheng Liu , Ping Hu","doi":"10.1016/j.taml.2022.100398","DOIUrl":"10.1016/j.taml.2022.100398","url":null,"abstract":"<div><p>A numerical model is presented in this article to investigate the interactions between laser generated ultrasonic and the microdefects (0.01 to 0.1 mm), which are on the surface of the laser powder bed fusion additive manufactured 316L stainless steel. Firstly, the influence of the transient sound field and detection positions on Rayleigh wave signals are investigated. The interactions between the varied microdefects and the laser ultrasonic are studied. It is shown that arrival time of reflected Rayleigh (RR) waves wave is only related to the location of defects. The depth can be checked from the feature point Q, the displacement amplitude and time delay of converted transverse (RS) wave, while the width information can be evaluated from the RS wave time delay. With the aid of fitting curves, it is found to be linearly related. This simulation study provides a theoretical basis for quantitative detection of surface microdefects of additive manufactured 316L stainless steel components.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100398"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000782/pdfft?md5=63604a6a53c0a05319279df70aa597b2&pid=1-s2.0-S2095034922000782-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46778561","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}
Zefeng Yu , Chenghang Han , Hang Yang , Yu Wang , Shan Tang , Xu Guo
{"title":"Elastoplastic constitutive modeling under the complex loading driven by GRU and small-amount data","authors":"Zefeng Yu , Chenghang Han , Hang Yang , Yu Wang , Shan Tang , Xu Guo","doi":"10.1016/j.taml.2022.100363","DOIUrl":"10.1016/j.taml.2022.100363","url":null,"abstract":"<div><p>In this paper, a data-driven method to model the three-dimensional engineering structure under the cyclic load with the one-dimensional stress-strain data is proposed. In this method, one-dimensional stress-strain data obtained under uniaxial load and different loading history is learned offline by gate recurrent unit (GRU) network. The learned constitutive model is embedded into the general finite element framework through data expansion from one dimension to three dimensions, which can perform stress updates under the three-dimensional setting. The proposed method is then adopted to drive numerical solutions of boundary value problems for engineering structures. Compared with direct numerical simulations using the J2 plasticity model, the stress-strain response of beam structure with elastoplastic materials under forward loading, reverse loading and cyclic loading were predicted accurately. Loading path dependent response of structure was captured and the effectiveness of the proposed method is verified. The shortcomings of the proposed method are also discussed.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100363"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000435/pdfft?md5=eb3173a33751c3f913e8e92f05dda63e&pid=1-s2.0-S2095034922000435-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43990834","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}
{"title":"Shapes of the fastest fish and optimal underwater and floating hulls","authors":"Igor Nesteruk","doi":"10.1016/j.taml.2022.100378","DOIUrl":"10.1016/j.taml.2022.100378","url":null,"abstract":"<div><p>A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern. The fastest fish have a very sharp convex nose (rostrum), the purpose of which remains unclear. The bodies of revolution similar to their shapes are analyzed in steady underwater and floating motion. The sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water surface. It was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface elevation. These fact allow diminishing the maximum pressure on the surface and wave drag. Special shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls.</p></div>","PeriodicalId":46902,"journal":{"name":"Theoretical and Applied Mechanics Letters","volume":"12 6","pages":"Article 100378"},"PeriodicalIF":3.4,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2095034922000587/pdfft?md5=e5ada91585b5014fa7717ab69fd5e22a&pid=1-s2.0-S2095034922000587-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48353951","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}