Accepted Date: 2021-09-07
Compressive properties and energy absorption of BCC lattice structures with bio-inspired gradient design
Fuchao Gao, Qinglei Zeng, Jing Wang, Zengfei Liu, Jun Liang
Abstract
Inspired by the gradient structure of the nature, two gradient lattice structures, i.e., unidirectional gradient lattice (UGL) and bidirectional gradient lattice (BGL), are proposed based on the body-centered cubic (BCC) lattice to obtain specially designed mechanical behaviors, such as load-bearing and energy absorption capacities. First, a theoretical model is proposed to predict the initial stiffness of the gradient lattice structure under compressive loading, and validated against quasi-stat...
Accepted Date: 2021-09-03
A comparative study of cluster-based methods at finite strain
Yang Yang, Lei Zhang, Shaoqiang Tang
Abstract
Virtual Clustering Analysis (VCA) is a reduced-order method for numerical homogenization. We formulate VCA for finite strain problems, illustrate its implementation, and provide numerical codes for free download and perusal. Comparison for four test examples shows that both VCA and Self-consistent Clustering Analysis (SCA) excellently approximate FFT-based direct numerical simulation (DNS) results, yet at much reduced numerical expenses. VCA is actually even faster at the online stage....
Accepted Date: 2021-09-02
Variation in contact load at the most loaded position of the outer raceway of a bearing in high-speed train gearbox
Yu Hou, Xi Wang, Hongbo Que, Rubing Guo, Xinhai Lin, Siqin Jin, Chengpan Wu, Yue Zhou, Xiaolong Liu
Abstract
For the fatigue failure and tribological property of a rolling element bearing, the contact load variation plays a significant role while the most loaded position of the bearing outer raceway takes the greatest risk of failure. This paper focuses on the variation in contact load on the most loaded position of the outer raceway of a gearbox bearing in high-speed train. Under operation conditions of different input speeds and torques, the dynamic contact load distribution in a gearbox bearing of h...
Accepted Date: 2021-08-30
The impact vibration behaviour of railway vehicles: a state-of-the-art overview
Lin Jing, Kaiyun Wang, Wanming Zhai
Abstract
The excessive vibrations of railway vehicles caused by dynamic impact loadings will greatly affect running safety and stability of trains; however, they are very difficult to be completely eliminated due to the complexity and diversity of railway lines and service environment. A comprehensive overview of recent studies on the impact vibration behaviour of railway vehicles was given in this paper. Firstly, the sources of impact excitations were classified and summarized in term of wheel-rail cont...
Accepted Date: 2021-08-18
Numerical Investigation of Efficient Synthetic Jets Generated by Multiple-frequency Actuating Signals
Yiran Lu, Jiangsheng Wang, Jinjun Wang
Abstract
The synthetic jets generated by multiple-frequency actuating signals composed of a basic sinusoidal wave and a superposed high-frequency signal is investigated by two-dimensional simulation in the present study. The effect of the frequency and amplitude of the high-frequency signal on the synthetic jet in the quiescent flow is investigated in detail with stroke length ratio L and Reynolds number 〖Re〗_(U_0 ) kept as constant. It is found that, with the high-frequency signal superposed, the vortex...
Accepted Date: 2021-08-13
Magnetically induced first-order composite beams incorporating couple stress and its flexoelectric effects
Gongye Zhang, Yilin Qu, Ziwen Guo, Feng Jin
Abstract
A new model of a first-order composite beam with flexoelectric and piezomagnetic layers is developed. The new model is under a transverse magnetic field and can capture the couple stress and its flexoelectric effects. The magnetically induced governing equations are obtained through a variational approach. To illustrate the new model, the static bending problem is analytically solved based on a Navier’s technique. The numerical results reveal that the extension, de?ection and shear deformation o...
Accepted Date: 2021-08-11
Review of Lagrangian stochastic models for turbulent combustion
Tianwei Yang, Yu Yin, Hua Zhou, Zhuyin Ren
Abstract
Predictive simulation of the combustion process in engine is crucial to understand the complex underlying physicochemical processes, improve engine performance, and reduce pollutant emissions. Key issues such as the physical modeling of the interaction between turbulence, chemistry and droplets, and the incorporation of the detailed chemistry in high-fidelity simulations of complex flows remain essential though challenging. This paper reviews the transported probability density function (PDF) me...
Accepted Date: 2021-08-09
Evaluating the Blast Mitigation Performance of Hard/Soft Composite Structures through Field Explosion Experiment and Numerical Analysis
Fengyuan Yang, Zhijie Li, Zhuo Zhuang, Zhanli Liu
Abstract
The application of hard/soft composite structure in personnel armor for blast mitigation is relatively practical and effective in realistic protection engineering, such as the shell/liner system of the helmet. However, there is still lacking a reliable experimental methodology to effectively evaluate the blast mitigation performance when the structure directly contacts the protected target, which limits the development of protection structures. In this paper, the blast mitigation performance of ...
Accepted Date: 2021-08-06
Hamilton-Pontryagin spectral-collocation methods for the orbit propagation
Zhonggui Yi, Baozeng Yue, Mingle Deng
Abstract
According to the discrete Hamilton-Pontryagin variational principle, we construct a class of variational integrators in the real vector spaces and extend to the Lie Groups for the left-trivialized Lagrangian mechanical systems by employing the spectral-collocation method to discretizing the corresponding Lagrangian and kinematic constraints. The constructed framework can be transformed easily to the well-known symplectic partitioned Runge-Kutta methods and the higher-order symplectic partitioned...
Accepted Date: 2021-08-01
Implementing fractional Fourier transform and solving partial differential equations using acoustic computational metamaterials in space domain
Zengyao Lv, Peng Liu, Yuanshuai Ding, Hangyu Li, Yongmao Pei
Abstract
Metamaterials can control incident waves in the sub-wavelength range through the design of artificial structures, and realize the functions that natural materials cannot achieve. The study of metamaterials has important theoretical value and application prospects. In recent years, the proposal of computational metamaterials has opened up a brand-new direction for analog computing, providing high-throughput, energy-free computing methods for special computing tasks. However, the development of ac...
Accepted Date: 2021-07-30
Design and Transition Characteristic Analysis of a Standard Model for Hypersonic Boundary Layer Transition Research
Shenshen Liu1;2, Xianxu Yuan1, Zhiyong Liu3, Qiang Yang1, Guohua Tu1, Xi Chen1, Yewei Gui1, Jianqiang Chen1;2
Abstract
To understand fundamental problems in hypersonic laminar-turbulent boundary layer transition (BLT) for three-dimensional (3D) complex vehicles, a new standard model with typical lifting-body features has been proposed, named as HyTRV (Hypersonic Transition Research Vehicle). The configuration of HyTRV is fully analytical, and details of the design process are discussed in this study. The transition characteristics for HyTRV are investigated using three combined methods, i.e., theoretical analyse...
Accepted Date: 2021-07-28
The geometry effect in reactive shock-elliptic bubble interactions
Dong-dong Li, Ge Wang, Bin Zhang, Zhi-bang Wang, Ben Guan
Abstract
he shock-induced ignition and detonation wave propagation in reactive elliptic premixed bubbles are numerically studied. Close attention is paid to the bubble geometry effect on the ignition pattern and the ensuing bubble behavior. Five elliptic bubbles with different aspect ratios are examined. According to the numerical results, three typical ignition patterns are identified under the same incident shock strength and the underlying mechanisms are interpreted. The difference in ignition pattern...
Accepted Date: 2021-07-27
Scaling analysis for the circulation growth of leading-edge vortex in flapping flight
Yang Xiang, Haotian Hang, Suyang Qin, Hong Liu
Abstract
n this paper, an experiment of a robotic model at Reynolds number of approximately 240 is performed with the aim of establishing a scaling law for describing the circulation growth of the leading edge vortex (LEV) on a flapping wing. Three typical modes of wing rotation, i.e., advanced, symmetric, and delayed modes, are considered to examine the effects of wing rotation on the scaling formation of LEV. The streamwise velocity fields of the LEV along the span of the wing are measured by particle ...
Accepted Date: 2021-07-23
Theoretical investigations on lattice Boltzmann method: an amended MBD and improved LBM
Jing Tang Xing
Abstract
This paper presents theoretical investigations of lattice Boltzmann method (LBM) to develop a completed LBM theory. Based on H-theorem with Lagrangian multiplier method, an amended theoretical equilibrium distribution function (EDF) is derived, which modifies the current Maxwell-Boltzmann distribution (MBD) to include the total internal energy as its parameter. This modification allows the three conservation laws derived directly from lattice Boltzmann equation (LBE) without additional small-par...
Accepted Date: 2021-07-14
Hybrid deep neural network based prediction method for unsteady flows with moving boundary
Ren-Kun Han, Zhong Zhang, Yi-Xing Wang, Zi-Yang Liu, Yang Zhang, Gang Chen
Abstract
Any motion, forced or free, of boundary affects the flow field around this boundary. A new kind of reduced order model (ROM) based on hybrid deep neural network is proposed to model flow field evolution process of unsteady flow around moving boundary. This hybrid deep neural network can map the relationship between the flow field at the next time step and the flow field and boundary positions at the previous time steps. Based on the learned information, the hybrid deep neural network can quickly...
Accepted Date: 2021-07-14
Studies on Theory and Modeling of Droplet and Spray Combustion in China-A Review
Zhou, Lixing
Abstract
Combustion phenomena were discovered still in far ancient time of China. From the 50’s of the last century, owing to the fast development of energy and power, aeronautical and astronautical, chemical and metallurgical engineering, combustion theory started to be studied in China. The Chinese scientists studied the theory of ignition, laminar flame propagation, droplet combustion and spray combustion. Later, from the 80’s of the last century, numerical modeling of combustion started to be studied...
Accepted Date: 2021-07-14
Coordinated motion of molecular motors on DNA chains with branch topology
Di Lu, Bin Chen
Abstract
Toward understanding the macroscopic mechanical behaviors of responsive DNA hydrogels integrated with DNA motors, here we construct the state map for the translocation process of a single FtsKC on a single DNA chain at the molecular level and then investigate the movement of single or multiple FtsKC motors on DNA chains with varied branch topology. Our studies indicate that multiple FtsKC motors can have coordinated motion, which is essentially due to the force responsive behavior of individual ...
Accepted Date: 2021-07-08
Reconstructing shock front of unstable detonations based on multi-layer perceptron
Lin Zhou, Honghui Teng, Hoi Dick Ng, Pengfei Yang, Zonglin Jiang
Abstract
The dynamics of frontal and transverse shocks in gaseous detonation waves is a complex phenomenon bringing many difficulties to both numerical and experimental research. Advanced laser-optical visualization of detonation structure may provide certain information of its reactive front, but the corresponding lead shock needs to be reconstructed building the complete flow field. Using the Multi-Layer Perceptron (MLP) approach, we propose a shock front reconstruction method which can predict evoluti...
Accepted Date: 2021-07-07
Tuning frictional properties of molecularly thin erucamide films through controlled self-assembling
Youyu Di, Shuai Zhang, Xi-Qiao Feng, Qunyang Li
Abstract
Self-assembled films (SAFs) have been proposed to be a promising candidate for molecularly thin lubricants. However, the frictional performance of SAFs is sensitively dependent on their molecular structures that are susceptible to external environments. Taking erucamide, a fatty amide widely used as a macroscale slip additive, as an example, we demonstrate that SAFs can be readily formed on various substrates, including silicon oxide, sapphire, copper and graphite. Through high-resolution topogr...
Accepted Date: 2021-07-06
Novel lift enhancement method based on zero-mass-flux jets and its adaptive controlling laws design
Zhijie Zhao, Zhenbing Luo, Bin Xu, Panfeng Zhang, Xiong Deng, Yuyan Guo,Wenqiang Peng,Shiqing Li
Abstract
For lessening the weight and volume of flow control system, enlarging the circulation control applying area of angle of attack (AOA) and achieving nice controlling characteristics, a novel lift enhancement method based on dual synthetic jet actuators (DSJAs) and synthetic jet actuator (SJA), and an adaptive PID algorithm based on radial basis function neural network are introduced. DSJAs are uniformly located along the chord to suppress the separation and trailing-edge SJA is applied to achieve ...
Accepted Date: 2021-07-01
A numerical investigation of the effects of turbulence on the ignition process in a turbulent MILD flame
Xiang Qian, Hao Lu, Chun Zou, Hanlin Zhang, Shujing Shao, Hong Yao
Abstract
In this study, we conduct three-dimensional nonlinear large-eddy simulation to investigate the interactions between turbulence and reaction during the initial ignition process of a turbulent methane/hydrogen jet-in-hot-coflow flame under moderate or intense low-oxygen dilution (MILD) condition. Special focus has been placed on the spatial development of the flame and the temporal evolution of representative ignition spots that characterize the range of ignition behaviors observed in the case. Re...
Accepted Date: 2021-06-29
Machine learning for adjoint vector in aerodynamic shape optimization
Mengfei Xu, Shufang Song, Xuxiang Sun, Wengang Chen, Weiwei Zhang
Abstract
Adjoint method is widely used in aerodynamic design because only once solution of flow field is required for adjoint method to obtain the gradients of all design variables. However, the calculation cost of adjoint vector is approximately equal to that of flow computation. In order to accelerate the solution of adjoint vector and improve the adjoint-based optimization efficiency, machine learning for adjoint vector modeling is presented. Deep neural network (DNN) is employed to construct the mapp...
Accepted Date: 2021-06-29
Effect of cooperative injection and suction jet on power extraction characteristics of a semi-active flapping airfoil
Jianyang Zhu, Mingkang Zhu, Tinghai Cheng
Abstract
A novel cooperative injection and suction jet was employed in this work to improve the power extraction characteristics of a semi-active flapping airfoil(S-AFA). The combined TAGUCHI method and numerical simulations was used to optimize the characteristic parameters of the cooperative injection and suction jet that affect the power extraction characteristics of the S-AFA. Under the Reynolds number of 6×104 and the pitching axis location at the center of the ellipse airfoil, the effects of the je...
Accepted Date: 2021-06-28
The rupture of a rubber sheet by a cavitation bubble: an experimental study
Xing-Yu Kan,Jia-Le Yan, Shuai Li,A-Man Zhang
Abstract
The dynamics of spark-generated cavitation bubbles near a deformable rubber sheet are experimentally investigated in this study. The transient bubble-rubber interaction is captured by high-speed photography, including the expansion and collapse of the bubble, jetting behaviors, large deformation, and the rubber sheet rupture. The dependence of the bubble behaviors and rubber response on two governing parameters (the bubble-rubber stand-off distance γ and the rubber thickness T) are systematicall...
Accepted Date: 2021-06-28
Biomechanical study on implantable and interventional medical devices
Lizhen Wang, Xili Ding, Wentao Feng, Yuanming Gao, Shudong Zhao, Yubo Fan
Abstract
Implants are used to repair human tissues or organs and restore their functions, including artificial joints, bone fixation devices, other orthopedic implants, and vascular interventional devices. Personalized and biodegradable implants are an irresistible trend in the clinic for implantable and interventional medical devices. Biomechanics play a vital role in the innovation of implants. Biodegradable implants have advantages of avoiding long-term complications, i.e., bone stress shielding, rest...
Accepted Date: 2021-06-22
Study on propellant management device in plate surface tension tanks
Shangtong Chen, Li Duan, Qi Kang
Abstract
Surface tension tanks exploit the liquid surface tension in liquid transport and gas-liquid separation to provide gas-free propellant for the thruster. High transport efficiency of deflectors can ensure liquid relocation in the microgravity environment within a short period of time, which is helpful for providing gas-free propellant. This paper explores transport efficiency of deflectors through drop tower experiments and numerical simulations with the Volume of Fluid (VOF) method. The experimen...
Accepted Date: 2021-06-15
Viscoelastic characterization and prediction of a wormlike micellar solution
Shuxin Huang
Abstract
A structure-based viscoelastic model was employed in the present paper to characterize and predict the viscoelastic properties of the wormlike micellar solution at 20 °C reported by Zhao et al. (2015), in which one structural parameter f is obtained with reference to the shear rate effect on the linear viscoelastic property and the other z to shear time and shear rate simultaneously. Both structural parameters are calculated by using linear interpolation method. The startup experiment can be des...
Accepted Date: 2021-06-07
Wave propagation in graphene reinforced piezoelectric sandwich nanoplates via high-order nonlocal strain gradient theory
Biao Hu, Juan Liu, Yuxing Wang, Bo Zhang, Huoming Shen
Abstract
Αn analytical method to explore the wave propagation characteristics of piezoelectric sandwich nanoplates was developed in the present work. The sandwich nanoplate is composed of a graphene reinforced composite core layer with two piezoelectric surface layers exposed to electric field. The material properties of the nanocomposite layer are given by the Halpin-Tsai model and mixture’s rule. The Euler-Lagrange equation of the nanoplate is obtained by Hamilton's principle and first-order shear defo...
Accepted Date: 2021-06-07
Length and stiffness effects of the attached flexible plate on the flow over a traveling wavy foil
Lin Tian, Zhiye Zhao, Wenjiang Wang
Abstract
Flow over a traveling wavy foil attached with a flexible plate has been numerically investigated using the lattice Boltzmann method combined with the immersed boundary method. The influence of the flexibility and length of the caudal fin on the locomotion of swimming fish through this simplified model, whereas the fish body is modeled by the undulating foil and the caudal fin by the plate passively flapping as a consequence of fluid-structure interaction. It is found that the plate flexibility d...
Accepted Date: 2021-06-02
Confined Thin Film Wrinkling on Shape Memory Polymer with Hybrid Surface Morphologies
Yu Wang, Jianliang Xiao
Abstract
With appropriate stimuli, such as heat, humidity, or magnetic field, shape memory polymers (SMPs) can recover to their original shapes from temporary, programmed states. Using thermal responsive SMPs as substrates, we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas. The bilayer system was fabricated by depositing a layer of aluminum thin ?lm on top of a SMP substrate programmed with a tensile strain. After the system was ...