K. Fujisaki, Ayane Kondo, K. Sasagawa, T. Moriwaki
{"title":"Development of compact pressing system for muscle activity evaluation in force myography","authors":"K. Fujisaki, Ayane Kondo, K. Sasagawa, T. Moriwaki","doi":"10.1299/mel.21-00283","DOIUrl":"https://doi.org/10.1299/mel.21-00283","url":null,"abstract":"","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"234 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124573947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The objective of this study is to quantify the influence of higher orders of expansion in the formulation of stochastic finite elements method on the linear elastic response in 2-dimensional problems with random physical parameters in the left hand side term. Neumann expansion was used to get an explicit expression of the result. Young’s modulus was considered as a random variable following normal distribution. The coefficient of variance (COV) of this input parameter ranged in this study up to 0.3 (30%), and mainly 20% of COV was analyzed. The displacement was selected as the quantity of interest. The difference in distribution function of the displacement for different orders of expansion was observed in the tail distribution. A fundamental example revealed the limitation of the applicability of first, second and third orders being approximately 3%, 12% and 20% of COV of input parameter. In the analysis of 2-phase composite material, the influence of geometrical random morphology was larger than that of physical parameter, but the latter was not negligible in the microscopic response.
{"title":"Influence of higher orders of Neumann expansion on accuracy of stochastic linear elastic finite element method with random physical parameters","authors":"L. Degeneve, N. Takano","doi":"10.1299/mel.20-00228","DOIUrl":"https://doi.org/10.1299/mel.20-00228","url":null,"abstract":"The objective of this study is to quantify the influence of higher orders of expansion in the formulation of stochastic finite elements method on the linear elastic response in 2-dimensional problems with random physical parameters in the left hand side term. Neumann expansion was used to get an explicit expression of the result. Young’s modulus was considered as a random variable following normal distribution. The coefficient of variance (COV) of this input parameter ranged in this study up to 0.3 (30%), and mainly 20% of COV was analyzed. The displacement was selected as the quantity of interest. The difference in distribution function of the displacement for different orders of expansion was observed in the tail distribution. A fundamental example revealed the limitation of the applicability of first, second and third orders being approximately 3%, 12% and 20% of COV of input parameter. In the analysis of 2-phase composite material, the influence of geometrical random morphology was larger than that of physical parameter, but the latter was not negligible in the microscopic response.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133098510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Keigo Shimizu, T. Nakashima, S. Sekimoto, K. Fujii, Takenori Hiraoka, Yusuke Nakamura, T. Nouzawa, Jun Ikeda, M. Tsubokura
In recent years, the dielectric barrier discharge plasma actuator (DBD-PA), which is a fluid control device, has been investigated for achieving both high aerodynamic performance and pleasing styling of transportation equipment. In this study, the authors installed a DBD-PA system on a simplified three-dimensional bluff automobile body to reduce the aerodynamic drag. In particular, the authors focused on the sides of the rear end of the body, where the local shape has high sensitivity regarding both styling and aerodynamic drag. At the rear sides of the automobile-like bluff body, a sharp edge rather than a smooth rounded corner often reduces the aerodynamic drag by promoting airflow separation. Therefore, the authors aimed to reduce the aerodynamic drag by using a DBD-PA system to promote flow separation at the rear end while retaining its rounded shape. Aerodynamic measurements using a one-fifth scale simplified automobile model were conducted in a wind tunnel. Preliminary investigation of the aerodynamic effect at the rear clarified how the longitudinal vortices from the rear pillar and the side edge of the trunk deck cause the drag increase at the rear-end corners. Two parallel DBD-PAs were installed on the rear surface to shift these vortices away from the corners by promoting flow separation. The drag reduction rate reached 3% at the highest applied voltage using the DBD-PA system on a rounded shape, and it achieved approximately half the effect of the sharp-edged shape. The longitudinal vortices were successfully kept away from the rear-end corners by the DBD-PAs. The surface pressure increased with the displacement of the vortices, which led to the drag reduction observed.
{"title":"Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator","authors":"Keigo Shimizu, T. Nakashima, S. Sekimoto, K. Fujii, Takenori Hiraoka, Yusuke Nakamura, T. Nouzawa, Jun Ikeda, M. Tsubokura","doi":"10.1299/mel.19-00354","DOIUrl":"https://doi.org/10.1299/mel.19-00354","url":null,"abstract":"In recent years, the dielectric barrier discharge plasma actuator (DBD-PA), which is a fluid control device, has been investigated for achieving both high aerodynamic performance and pleasing styling of transportation equipment. In this study, the authors installed a DBD-PA system on a simplified three-dimensional bluff automobile body to reduce the aerodynamic drag. In particular, the authors focused on the sides of the rear end of the body, where the local shape has high sensitivity regarding both styling and aerodynamic drag. At the rear sides of the automobile-like bluff body, a sharp edge rather than a smooth rounded corner often reduces the aerodynamic drag by promoting airflow separation. Therefore, the authors aimed to reduce the aerodynamic drag by using a DBD-PA system to promote flow separation at the rear end while retaining its rounded shape. Aerodynamic measurements using a one-fifth scale simplified automobile model were conducted in a wind tunnel. Preliminary investigation of the aerodynamic effect at the rear clarified how the longitudinal vortices from the rear pillar and the side edge of the trunk deck cause the drag increase at the rear-end corners. Two parallel DBD-PAs were installed on the rear surface to shift these vortices away from the corners by promoting flow separation. The drag reduction rate reached 3% at the highest applied voltage using the DBD-PA system on a rounded shape, and it achieved approximately half the effect of the sharp-edged shape. The longitudinal vortices were successfully kept away from the rear-end corners by the DBD-PAs. The surface pressure increased with the displacement of the vortices, which led to the drag reduction observed.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130384084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents numerical solution to a shape optimization for stationary fluid structure interactive fields. In the fluid structure interactive analysis, a weak coupled analysis is used to alternately analyze the governing equations of the flow field domain and the structural field considering geometrically nonlinear. A mean compliance minimization problem is formulated in order to achieve sti ff ness maximization on the structural field. Shape derivative, which means the sensitivity in the shape optimization problem, is derived theoretically by using the Lagrange multiplier method and adjoint variable method, and the formulae of the shape derivative with respect to domain variation of the distribution function. Reshaping is carried out by the H 1 gradient method proposed as an approach to solving shape optimization problems. Numerical analysis program for the problem is developed by using FreeFEM, and validity of proposed method is confirmed by numerical results of 2D problems.
{"title":"Shape optimization for stiffness maximization of geometrically nonlinear structure by considering fluid-structure-interaction","authors":"E. Katamine, Ryuga Kawai, Minori Takahashi","doi":"10.1299/MEL.21-00048","DOIUrl":"https://doi.org/10.1299/MEL.21-00048","url":null,"abstract":"This paper presents numerical solution to a shape optimization for stationary fluid structure interactive fields. In the fluid structure interactive analysis, a weak coupled analysis is used to alternately analyze the governing equations of the flow field domain and the structural field considering geometrically nonlinear. A mean compliance minimization problem is formulated in order to achieve sti ff ness maximization on the structural field. Shape derivative, which means the sensitivity in the shape optimization problem, is derived theoretically by using the Lagrange multiplier method and adjoint variable method, and the formulae of the shape derivative with respect to domain variation of the distribution function. Reshaping is carried out by the H 1 gradient method proposed as an approach to solving shape optimization problems. Numerical analysis program for the problem is developed by using FreeFEM, and validity of proposed method is confirmed by numerical results of 2D problems.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"07 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124483057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Takaaki Yasui, Fumihiro Akatsuka, Y. Nomura, T. Sugiura
Focusing on humans’ velocity perceptual characteristics, this study clarified the velocity JNDs that is minimal velocity differences humans can discriminate. For this purpose, using a 2-DOF SCARA-type haptic device, we conducted an experiment, assuming a pattern in which velocities were increased from constant values to other constant ones for shoulder and/or elbow joints. In the experiment, subjects’ upper limbs were enforced to move by the device, while the subjects focused on their hand velocity change using their proprioceptive sensations. After the movements, the subjects answered whether they perceived a velocity change during the movement. Iterating this trial with various velocity difference, velocity JNDs were obtained for each of the subjects and the following two factors. The two factors to be evaluated were the joint factor and the before-acceleration velocity factor: (1) the joint factor was the joints to be moved, of which levels were set as the shoulder, the elbow, and the shoulder-and-elbow, (2) the before-acceleration velocity factor was the nearly-constant tangential velocity of hand motions before velocity change, Vbefore. As a result, it was confirmed that a linear relationship of the velocity JND against the Vbefore was confirmed for all the joint factor levels, i.e., the shoulder only, the elbow only, and both the shoulder-and-elbow. Here, it should be noted that the joint angular velocities corresponding to hand tangential velocities are greatly different between the three joint factor levels. Nevertheless, the correspondence between Vbefore and the velocity JNDs were approximately the same between the three jointfactor levels. Therefore, it is concluded that the hand velocities, not the joint angular velocities, are dominant in human velocity-change perception for passive movements in the shoulder and/or elbow joint.
{"title":"Human velocity-change perceptual characteristics in passive movements of shoulder and/or elbow joint","authors":"Takaaki Yasui, Fumihiro Akatsuka, Y. Nomura, T. Sugiura","doi":"10.1299/mel.18-00503","DOIUrl":"https://doi.org/10.1299/mel.18-00503","url":null,"abstract":"Focusing on humans’ velocity perceptual characteristics, this study clarified the velocity JNDs that is minimal velocity differences humans can discriminate. For this purpose, using a 2-DOF SCARA-type haptic device, we conducted an experiment, assuming a pattern in which velocities were increased from constant values to other constant ones for shoulder and/or elbow joints. In the experiment, subjects’ upper limbs were enforced to move by the device, while the subjects focused on their hand velocity change using their proprioceptive sensations. After the movements, the subjects answered whether they perceived a velocity change during the movement. Iterating this trial with various velocity difference, velocity JNDs were obtained for each of the subjects and the following two factors. The two factors to be evaluated were the joint factor and the before-acceleration velocity factor: (1) the joint factor was the joints to be moved, of which levels were set as the shoulder, the elbow, and the shoulder-and-elbow, (2) the before-acceleration velocity factor was the nearly-constant tangential velocity of hand motions before velocity change, Vbefore. As a result, it was confirmed that a linear relationship of the velocity JND against the Vbefore was confirmed for all the joint factor levels, i.e., the shoulder only, the elbow only, and both the shoulder-and-elbow. Here, it should be noted that the joint angular velocities corresponding to hand tangential velocities are greatly different between the three joint factor levels. Nevertheless, the correspondence between Vbefore and the velocity JNDs were approximately the same between the three jointfactor levels. Therefore, it is concluded that the hand velocities, not the joint angular velocities, are dominant in human velocity-change perception for passive movements in the shoulder and/or elbow joint.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115850872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nonlinear short-term prediction incorporating modeling technique is used in various fields such as stock prices, exchange, daily temperature and power demand, and is one of the crucial research topics. Radial basis function (RBF) network, which is one of the artificial neural networks (ANNs), is widely used for the modeling and prediction (He and Lapedes, 1993; Rosupal et al., 1998; Gan et al., 2012). Kondo used an ANN with four layers for modeling and prediction of Sulfur Dioxide (SO2) (Kondo, 1993), in which he reported that highly accurate prediction could be made by the ANN in comparison with a linear regression model and an auto-regressive (AR) model. Cowper et al. adopted the RBF network for nonlinear modeling and prediction (Cowper et al., 2002), in which they pointed out that the width of Gaussian kernel was a key factor for highly accurate modeling and prediction using the RBF network. They adopted a simple estimate for the width proposed by Haykin (1994), and the validation of normalization of Gaussian kernel was discussed. Du and Zhang also adopted the RBF network for modeling and prediction (Du and Zhang, 2008), in which genetic algorithm (GA) was used to optimize several parameters (the width and center of Gaussian kernel, the number of hidden layers) in the RBF network unlike Cowper et al. (Cowper et al., 2002). Manjunatha et al. adopted the RBF network for predicting diesel engine emissions, and concluded that the highly accurate prediction could be made in comparison with back propagation neural network (Manjunatha et al., 2012). Based on the above review, we developed a system for modeling and prediction using the RBF network and applied it to several benchmarks. Here, as an illustrative example, let us consider Mackey-Glass delay-differential equation given by Eq. (1).
结合建模技术的非线性短期预测应用于股票价格、交易所、日常温度和电力需求等各个领域，是重要的研究课题之一。径向基函数(RBF)网络是人工神经网络(ann)的一种，广泛用于建模和预测(He and Lapedes, 1993;Rosupal等人，1998;Gan et al.， 2012)。Kondo使用四层人工神经网络对二氧化硫(SO2)进行建模和预测(Kondo, 1993)，他在其中报告说，与线性回归模型和自回归(AR)模型相比，人工神经网络可以做出高度准确的预测。Cowper等人采用RBF网络进行非线性建模和预测(Cowper et al.， 2002)，他们指出高斯核的宽度是使用RBF网络进行高精度建模和预测的关键因素。他们采用Haykin(1994)提出的宽度的简单估计，并讨论了高斯核归一化的验证。Du和Zhang也采用RBF网络进行建模和预测(Du和Zhang, 2008)，与Cowper等人(Cowper et al.， 2002)不同的是，该网络采用遗传算法(GA)对RBF网络中的几个参数(高斯核的宽度和中心、隐藏层的数量)进行优化。Manjunatha等人采用RBF网络预测柴油机排放，与反向传播神经网络相比，预测精度较高(Manjunatha et al.， 2012)。基于以上回顾，我们开发了一个使用RBF网络进行建模和预测的系统，并将其应用于几个基准测试。这里，作为一个说明性的例子，让我们考虑由Eq.(1)给出的Mackey-Glass延迟微分方程。
{"title":"Nonlinear prediction using radial basis function network incorporating coordinate transformation","authors":"S. Kitayama, Kanako Tamada, Y. Kanno","doi":"10.1299/MEL.18-00517","DOIUrl":"https://doi.org/10.1299/MEL.18-00517","url":null,"abstract":"Nonlinear short-term prediction incorporating modeling technique is used in various fields such as stock prices, exchange, daily temperature and power demand, and is one of the crucial research topics. Radial basis function (RBF) network, which is one of the artificial neural networks (ANNs), is widely used for the modeling and prediction (He and Lapedes, 1993; Rosupal et al., 1998; Gan et al., 2012). Kondo used an ANN with four layers for modeling and prediction of Sulfur Dioxide (SO2) (Kondo, 1993), in which he reported that highly accurate prediction could be made by the ANN in comparison with a linear regression model and an auto-regressive (AR) model. Cowper et al. adopted the RBF network for nonlinear modeling and prediction (Cowper et al., 2002), in which they pointed out that the width of Gaussian kernel was a key factor for highly accurate modeling and prediction using the RBF network. They adopted a simple estimate for the width proposed by Haykin (1994), and the validation of normalization of Gaussian kernel was discussed. Du and Zhang also adopted the RBF network for modeling and prediction (Du and Zhang, 2008), in which genetic algorithm (GA) was used to optimize several parameters (the width and center of Gaussian kernel, the number of hidden layers) in the RBF network unlike Cowper et al. (Cowper et al., 2002). Manjunatha et al. adopted the RBF network for predicting diesel engine emissions, and concluded that the highly accurate prediction could be made in comparison with back propagation neural network (Manjunatha et al., 2012). Based on the above review, we developed a system for modeling and prediction using the RBF network and applied it to several benchmarks. Here, as an illustrative example, let us consider Mackey-Glass delay-differential equation given by Eq. (1).","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125902166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we developed a method for obtaining high contributing part (reference point) to the response point at the operational condition by operational TPA (OTPA) using several measurement systems. OTPA calculates contribution of each reference point to the response point using only operational signals. All reference and response signals are necessary to be measured simultaneously by single measurement system because the method calculates the contribution using their correlation along time. However, this occasionally requires preparing large measurement system depending on the number of measurement points and the size of products. This may decrease the applicability of the method. We then considered a post processing procedure to obtain accurate contribution of each reference point to the response point by using several measurement systems instead of preparing large single measurement system. In the proposed method, all signals are measured using different several systems at around same timing. The exact sampling timing gaps among systems are estimated by using the estimation error between the calculated and actual measured response signal. After then, all reference signals compensated by the estimated time gap in each system are regarded to be measured simultaneously and contribution of all reference signals are calculated by OTPA. As the verification of the proposed method, the procedure was applied to a simple vehicle model. As the result, the contribution of the proposed method was similar with the contribution by single measurement system and clarified to have an ability to obtain correct contribution by several measurement systems.
{"title":"Operational transfer path analysis method using several measurement systems","authors":"J. Yoshida, Takashi Yamamoto, Yuta Nozuchi","doi":"10.1299/mel.21-00163","DOIUrl":"https://doi.org/10.1299/mel.21-00163","url":null,"abstract":"In this study, we developed a method for obtaining high contributing part (reference point) to the response point at the operational condition by operational TPA (OTPA) using several measurement systems. OTPA calculates contribution of each reference point to the response point using only operational signals. All reference and response signals are necessary to be measured simultaneously by single measurement system because the method calculates the contribution using their correlation along time. However, this occasionally requires preparing large measurement system depending on the number of measurement points and the size of products. This may decrease the applicability of the method. We then considered a post processing procedure to obtain accurate contribution of each reference point to the response point by using several measurement systems instead of preparing large single measurement system. In the proposed method, all signals are measured using different several systems at around same timing. The exact sampling timing gaps among systems are estimated by using the estimation error between the calculated and actual measured response signal. After then, all reference signals compensated by the estimated time gap in each system are regarded to be measured simultaneously and contribution of all reference signals are calculated by OTPA. As the verification of the proposed method, the procedure was applied to a simple vehicle model. As the result, the contribution of the proposed method was similar with the contribution by single measurement system and clarified to have an ability to obtain correct contribution by several measurement systems.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129135744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Baby carriage vibrations cause unpleasant sensations for both the babies and carriage operators. This study analyzed the baby carriage vibration generated by passing over a level difference on a road surface because this situation introduces a large physical burden and significant stress. The purpose of this study is to develop simulation models in order to improve the performances of baby carriages under operating conditions efficiently. Furthermore, experiments were conducted using a real baby carriage to verify the accuracy of the simulation models. We focused on vibrations in the front leg because characteristic vibrations were generated in this part. Baby carriage models, such as the rigid body model (modeled as a rigid body other than the elastic deformation of suspension) and the elastic connection model (modeled the movement of joints around the legs), have been developed. However, the accuracy of these models are insufficient because these are not able to model high-frequency vibrations and the trend in the vibration peaks when the baby carriage passes over the level difference. Additionally, we developed the front leg elastic body model considered the elastic deformation of front legs based on the finite segment method. In the front leg elastic body model, front legs were divided into fifths, which were connected by translational and rotational springs because the time is required for analysis using the general finite element method. This model was able to provide the trend similar to the experimental result. Finally, the vibration reduction design for a baby carriage was considered by using the developed simulation model.
{"title":"Dynamic simulation of baby carriage under running condition: analyzing vibration when passing over a level difference","authors":"Chihiro Kamio, T. Aihara","doi":"10.1299/mel.19-00376","DOIUrl":"https://doi.org/10.1299/mel.19-00376","url":null,"abstract":"Baby carriage vibrations cause unpleasant sensations for both the babies and carriage operators. This study analyzed the baby carriage vibration generated by passing over a level difference on a road surface because this situation introduces a large physical burden and significant stress. The purpose of this study is to develop simulation models in order to improve the performances of baby carriages under operating conditions efficiently. Furthermore, experiments were conducted using a real baby carriage to verify the accuracy of the simulation models. We focused on vibrations in the front leg because characteristic vibrations were generated in this part. Baby carriage models, such as the rigid body model (modeled as a rigid body other than the elastic deformation of suspension) and the elastic connection model (modeled the movement of joints around the legs), have been developed. However, the accuracy of these models are insufficient because these are not able to model high-frequency vibrations and the trend in the vibration peaks when the baby carriage passes over the level difference. Additionally, we developed the front leg elastic body model considered the elastic deformation of front legs based on the finite segment method. In the front leg elastic body model, front legs were divided into fifths, which were connected by translational and rotational springs because the time is required for analysis using the general finite element method. This model was able to provide the trend similar to the experimental result. Finally, the vibration reduction design for a baby carriage was considered by using the developed simulation model.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132794047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We realized a direct numerical simulation (DNS) of the turbulent flow of liquid along a solid wall with solidification by incorporating the phase-field model. The combination of DNS and phase-field model can clarify the mechanism of modulation of a turbulent boundary layer of liquid solidifying upon a solid wall and assist in constructing a prediction method in the future. The simulations allow observation of turbulent flow along a solid wall surface that grows with the solidification of a flowing liquid under an undercooling condition. In the flow field, turbulence structures such as velocity streaks and quasi-streamwise vortices were noted to diminish, and the turbulent flow tended to be laminar. In contrast, there were no changes in the turbulence statistics in the region above the growing solid–liquid interface. The solidification structure had a bent shape, which was caused by the e ff ects of advection downstream and growing in the upstream direction owing to the undercooled fluid flowing from upstream. The wall surface grew non-uniformly depending on the local flow patterns and temperature distribution caused by turbulence structures close to the wall surface. The complex shape of the wall surface, which was observed during simulation, was originally triggered by the initial distribution of the turbulence structures. Sweep events in the high-speed streaks relatively expedited the growth of the solidification structures, which then modified the turbulence structures. The interaction between the turbulence structure and solidification structure promotes laminarization of the fluid flow.
{"title":"Direct numerical simulation of solidifying liquid turbulence using the phase-field model","authors":"T. Ohta, T. Ichiyanagi, Taisei Tanaka","doi":"10.1299/mel.20-00327","DOIUrl":"https://doi.org/10.1299/mel.20-00327","url":null,"abstract":"We realized a direct numerical simulation (DNS) of the turbulent flow of liquid along a solid wall with solidification by incorporating the phase-field model. The combination of DNS and phase-field model can clarify the mechanism of modulation of a turbulent boundary layer of liquid solidifying upon a solid wall and assist in constructing a prediction method in the future. The simulations allow observation of turbulent flow along a solid wall surface that grows with the solidification of a flowing liquid under an undercooling condition. In the flow field, turbulence structures such as velocity streaks and quasi-streamwise vortices were noted to diminish, and the turbulent flow tended to be laminar. In contrast, there were no changes in the turbulence statistics in the region above the growing solid–liquid interface. The solidification structure had a bent shape, which was caused by the e ff ects of advection downstream and growing in the upstream direction owing to the undercooled fluid flowing from upstream. The wall surface grew non-uniformly depending on the local flow patterns and temperature distribution caused by turbulence structures close to the wall surface. The complex shape of the wall surface, which was observed during simulation, was originally triggered by the initial distribution of the turbulence structures. Sweep events in the high-speed streaks relatively expedited the growth of the solidification structures, which then modified the turbulence structures. The interaction between the turbulence structure and solidification structure promotes laminarization of the fluid flow.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127836243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Uemura, T. Sasabe, Y. Tabuchi, Junko Kurihara, T. Jao, S. Hirai
Lithium-ion secondary batteries have become key devices for energy storage for automotive and renewable energy applications. To further improve battery performance, clarification of the ion transport phenomena within the batteries is necessary. However, experimental investigation has not yet been performed. In this study, in situ visualization of lithium-ion batteries with a hard carbon or graphite negative electrode was achieved using low-energy X-ray microscopy. Visualization experiments were conducted on two different negative electrode materials. The concentration distributions of lithium ions (Li + ) and hexafluorophosphate ions (PF6 − ) inside the hard carbon negative electrode were investigated. Additionally, stage transformation caused by lithium intercalation was observed in the graphite negative electrode. These results suggest that transport phenomena in the electrodes of operating lithium-ion batteries can be investigated using low-energy X-ray microscopy.
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