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Accepted Manuscript
[Abstract] (3) [FullText HTML] (3) [PDF 2874KB] (0)
Abstract:
The specific sign of Reynolds stress in the boundary layer on a flat plate at zero incidence is newly interpreted in present paper based on the theory of vortex-induced vortex. It avoids some problems appeared in a traditional explanation, on the basis of relationship between mean and fluctuating flows due to the transport of momentum. Through the analysis of local flow field in the immediate neighborhood of wall, the characteristics of Reynolds stress are identified through introducing turbulence-induced small-scale streamwise eddies above the flat plate. The positive Reynolds stress is theoretically verified. And such new interpretation illustrates that the generation of Reynolds stress, as well as fluctuating velocity, is intrinsically independent of the mean flow. But its specific sign would be determined by the mean flow due to the inertial forces. Other features, such as the intensity relationship among three components of fluctuating velocity, are also presented.
Accepted Manuscript
[Abstract] (3) [FullText HTML] (1) [PDF 2624KB] (1)
Abstract:
This paper presents a simple nonparametric regression approach to data-driven computing in elasticity. We apply the kernel regression to the material data set, and formulate a system of nonlinear equations solved to obtain a static equilibrium state of an elastic structure. Preliminary numerical experiments illustrate that, compared with existing methods, the proposed method finds a reasonable solution even if data points distribute coarsely in a given material data set.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.009
[Abstract] (86) [FullText HTML] (25) [PDF 2807KB] (6)
Abstract:
This letter reports inlet flow disturbance effects on direct numerical simulation of incompressible round jet at Reynolds number 2500. The simulation employs an accurate projection method in which a sixth order biased upwind difference scheme is used for spatial discretization of nonlinear convective terms, with a fourth order central difference scheme used in the discretization of the divergence of intermediate velocity. Carefully identifying reveals that the inlet flow disturbance has some influences on the distribution pattern of mean factor of swirling strength intermittency. With the increase of inlet disturbance magnitude jet core cone slightly shortens, observable differences occur in the centerline velocity and its fluctuations, despite the negligible impacts on the least square fitted centerline velocity decay constant (Bu) and distribution parameter (Ku) for velocity profile in self-similar region.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.007
[Abstract] (108) [FullText HTML] (40) [PDF 3697KB] (21)
Abstract:
The pore configuration in porous medium is assumed to be the randomly distributed cube-like particles which can overlap each other in the periodic cubic domain, and the impact of particle characteristics on the percolation property of these cube-like particle packing systems is analyzed. Firstly, by combining the percolation models and finite-size scaling analysis, three numerical parameters (i.e., percolation transition width \begin{document}$\Delta$\end{document} L, local percolation threshold \begin{document}$\psi$\end{document} c(L), and correlation length exponent \begin{document}$\nu$\end{document} ) for the cube-like particle systems with shape parameter s in [1.0, \begin{document}$+\infty$\end{document} ] are derived successively. Then, based on the relation between the percolation threshold \begin{document}$\psi$\end{document} c in infinite space and the local percolation threshold \begin{document}$\psi$\end{document} c(L), the corresponding \begin{document}$\psi$\end{document} c with s in [1.0, \begin{document}$+\infty$\end{document} ] are further determined. It is shown from the study that the characteristics of cube-like particles have significant influence on the global percolation threshold \begin{document}$\psi$\end{document} c of the particle packing systems. As the parameter s increases from 1.0 to \begin{document}$+\infty$\end{document} , the percolation threshold \begin{document}$\psi$\end{document} c will go down persistently. When the surface of cube-like particles is cubical and spherical, respectively, the minimum and maximum thresholds \begin{document}$\psi$\end{document} c,min and \begin{document}$\psi$\end{document} c,max are obtained.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.004
[Abstract] (137) [FullText HTML] (46) [PDF 4235KB] (16)
Abstract:
A visualized investigation was carried out on the effect of the diverging angle on the bubble motion and interfacial behavior in a Venturi-type bubble generator. It was found two or three large vortexes formed in the diverging section, resulting in strong reentrant jet flow in the front of the bubbles or slugs rushing out of the throat. The jet flow in return bumps into the ongoing bubbles or slugs, leading to strong interaction between the gas and liquid phases. The diverging angle has significant influence on the reentrant flow process and the performance of the bubble generator as well. Increasing the diverging angle results in the reentrant flow moving further forward to the upstream and intensifies the interaction between the two phases. As a consequence, the breakup or collapse of bubbles becomes more violent, whereby finer bubbles are generated. As such, the reentrant flow strongly links to the performance of the Venturi channel taken as a bubble generator, and that a moderate increase in the diverging angle can improve its performance without additional increase in flow resistance like that by increasing liquid flow rate.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.003
[Abstract] (53) [FullText HTML] (28) [PDF 2728KB] (7)
Abstract:
Lattice Boltzmann method is one of the widely used in multiphase fluid flow. However, the two main disadvantages of this method are the instability of numerical calculations due to the large density ratio of two phases and impossibility of the temperature distribution to be fed back into the velocity distribution function when the temperature is simulated. Based on the combination prescribed by Inamuro, the large density ratio two-phase flow model and thermal model makes the density ratio of the model simulation to be increased to 2778:1 by optimizing the interface distribution function of two-phase which improves the accuracy of differential format. The phase transition term is added as source term into the distribution function controlling two phase order parameters to describe the temperature effect on the gas-liquid phase transition. The latent heat generated from the phase change is also added as a source term into the temperature distribution function which simulates the movement of the flow under the common coupling of density, velocity, pressure and temperature. The density and the temperature distribution of single bubble are simulated. Comparison of the simulation results with experimental results indicates a good agreement pointing out the effectiveness of the improved model.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.006
[Abstract] (78) [FullText HTML] (32) [PDF 3252KB] (6)
Abstract:
The intrinsic physical relationship of vorticity between modes A and B in the three-dimensional wake transition is investigated. Direct numerical simulations for the flow past a square-section cylinder are carried out at Reynolds numbers of 180 and 250, associated with modes A and B, respectively. Based on the analysis of spacial distributions of vorticity in the near wake, characteristics of the vertical vorticity in modes A and B are identified. Moreover, the relationship of three vorticity components with specific signs is summarized into two sign laws, as intrinsic physical relationships between two instability modes. By the theory of vortex-induced vortex, such two sign laws confirm that there are two and only two kinds of vortex-shedding patterns in the near wake, just corresponding to modes A and B. In brief, along the free stream direction, mode A can be described by the parallel shedding vertical vortices with the same sign, while mode B is described by the parallel shedding streamwise vortices with the same sign. Finally, it is found out that the \begin{document}$\Pi$\end{document} -type vortex is a basic kind of vortex structure in both modes A and B.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.002
[Abstract] (71) [FullText HTML] (41) [PDF 2589KB] (8)
Abstract:
Dropshafts are vertical structures widely used in urban drainage systems and buildings for water transportation. In this paper, a physical model study was conducted to investigate the air entrainment in the dropshaft under various flow regimes with and without air ventilation. Observed from the experiments, the air entrainment mechanisms varied with the water flow regimes in the dropshaft. When there was no water plug formed in the dropshaft, air could be supplied directly from downstream. Once the water plug was formed, while without venting, the air was replenished only from downstream intermittently and then in the form of large air bubble traveling upwards to the airspace at the top; while with venting, air was mainly replenished from the dropshaft top and no large air bubble was observed. The experimental results also showed that the amount of entrained air in the dropshaft with venting was greater than that without venting.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.001
[Abstract] (48) [FullText HTML] (33) [PDF 3503KB] (3)
Abstract:
Reaction-diffusion (RD) equation was often used to investigate the pattern dynamics, but telegraph reaction-diffusion (TRD) system was seldom studied. In this paper, the Izhikevich model was modified to explain some biological mechanisms by RD and TRD in neuronal cluster. Then a new condition under which the system loses stability was proposed and the effect of parameters, diffusion, memory and steady state were considered on the process of neuronal spiking. The method presented is a novel approach to investigate the pattern dynamics of biological systems. Finally, simulations are carried out to validate our theoretical results.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.008
[Abstract] (28) [FullText HTML] (25) [PDF 2386KB] (6)
Abstract:
We solve the local uniaxial tension of an infinite rod in the framework of non-ordinary state-based peridynamics. The singular solutions of stress and displacement are acquired. When the influencing range of the window function approaches zero, these two solutions will return to the solutions of the classical elasticity. The analysis shows that the singularities of the solutions stem from such a feature of the window function that must be represented by a rapidly decreasing function in physics. Contrary to the classical elasticity, the stress solution of peridynamics is smoother than the displacement solution. In addition, a criterion used to select the window function is proposed in this paper.
Uncorrected proof , doi: 10.1016/j.taml.2018.05.005
[Abstract] (47) [FullText HTML] (27) [PDF 4189KB] (4)
Abstract:
Traffic rule is a key factor affecting traffic flow and safety. We develop our models, including the cellular automata traffic flow model as well as the linear regression one, aiming at calculating traffic flow and evaluating safety conditions with varied traffic rules. Then, we thoroughly investigate four types of paths in a freeway, namely two straight lanes, three straight lanes, ramps, and roundabouts as case studies and discuss the different traffic rules as comparison. The results demonstrate that " Keep-Right-Except-To-Pass” rule is not as effective as the free rule in promoting traffic flow; however, this rule ensures safety for drivers better than the free rule. Additionally, a new traffic rule, which sets different posted speed limits for adjacent lanes, is proposed to promote better traffic flow with safety requirements satisfied. Furthermore, we apply effective rules and alternatives, left driving norms as well as intelligent system as extension and obtain better results. Finally, model’s sensitivity analysis regarding to probability of decelerating and posted speed limits proves the stability of our results.
Accepted Manuscript
[Abstract] (6) [FullText HTML] (3) [PDF 2433KB] (0)
Abstract:
The current structure-preserving theory, including the symplectic method and the multi-symplectic method, pays most attention on the conservative properties of the continuous systems because that the conservative properties of the conservative systems can be formulated in the mathematical form. But, the nonconservative characteristics are the nature of the systems existing in engineering. In this letter, the structure-preserving approach for the infinite dimensional nonconservative systems is proposed based on the generalized multi-symplectic method to broaden the application fields of the current structure-preserving idea. In the numerical examples, two nonconservative factors, including the strong excitation on the string and the impact on the cantilever, are considered respectively. The vibrations of the string and the cantilever are investigated by the structure-preserving approach and the good long-time numerical behaviors as well as the high numerical precision of which are illustrated by the numerical results presented.
Uncorrected proof , doi: 10.1016/j.taml.2018.06.003
[Abstract] (29) [FullText HTML] (21) [PDF 2795KB] (7)
Abstract:
The dynamic behavior of two-dimensional nanostructures is important to the future application of nano devices. The vibrational behaviors of single-layered hexagonal boron nitride (h-BN) are studied by molecular dynamics simulation and continuum plate model. The bending stiffness and Poisson’s ratios of h-BN along zigzag direction and armchair direction are calculated. H-BN is softer compared with graphene. The continuum plate model can predict the vibration of h-BN with four edge-clamped boundary conditions well. The electric fields in different directions have obvious influence on the vibration of h-BN. The natural frequency of h-BN changes linearly with the electric field intensity along the polarization direction. The natural frequency of h-BN decreases with the increase of electric field intensity along both positive and negative non-polarization direction. While the natural frequency of h-BN increases with the increase of electric field intensity along both positive and negative transverse electric field.
Uncorrected proof , doi: 10.1016/j.taml.2018.06.001
[Abstract] (54) [FullText HTML] (18) [PDF 3879KB] (5)
Abstract:
The linear and nonlinear dynamic responses of a vibratory ring gyroscope are investigated in this study focusing on the response mechanism of such a vibratory gyroscope. It is found that the nonlinear equations governing the drive and sense directions are coupled through both inertial linear and geometric nonlinear terms. Nonlinear responses are studied based on the full coupled nonlinear dynamic equations. The varying amplitude on the sense direction is analyzed for different input angular rates. The effect of nonlinearity on the ring gyroscope system is performed by comparing the results of nonlinear responses to those of linear responses. The contributions of some parameters to the amplitude responses and gyroscope sensitivity are analyzed, the conclusions of which provide guidelines to improve the sensitivity of the vibratory ring gyroscopes.

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2018, 8(4): 209 -230.   doi: 10.1016/j.taml.2018.04.010
[Abstract] (206) [FullText HTML] (42) [PDF 3780KB] (8)
Abstract:
In a vast number of engineering fields like medicine, aerospace or robotics, materials are required to meet unusual performances that simple homogeneous materials are often not able to fulfil. Consequently, many efforts are currently devoted to develop future generations of materials with enhanced properties and unusual functionalities. In many instances, biological systems served as a source of inspiration, as in the case of cellular materials. Commonly observed in nature, cellular materials offer useful combinations of structural properties and low weight, yielding the possibility of coexistence of what used to be antagonistic physical properties within a single material. Due to their peculiar characteristics, they are very promising for engineering applications in a variety of industries including aerospace, automotive, marine and constructions. However, their use is conditional upon the development of appropriate constitutive models for revealing the complex relations between the microstructure's parameters and the macroscopic behavior. From this point of view, a great variety of analytical and numerical techniques have been proposed and exhaustively discussed in recent years. Noteworthy contributions, suggesting different assumptions and techniques are critically presented in this review paper.
2018, 8(4): 231 -244.   doi: 10.1016/j.taml.2018.04.008
[Abstract] (204) [FullText HTML] (76) [PDF 4064KB] (11)
Abstract:
Stochastic dynamic analysis of the nonlinear system is an open research question which has drawn many scholars' attention for its importance and challenge. Fokker–Planck–Kolmogorov (FPK) equation is of great significance because of its theoretical strictness and computational accuracy. However, practical difficulties with the FPK method appear when the analysis of multi-degree-of-freedom (MDOF) with more general nonlinearity is required. In the present paper, by invoking the idea of equivalence of probability flux, the general high-dimensional FPK equation related to MDOF system is reduced to one-dimensional FPK equation. Then a cell renormalized method (CRM) which is based on the numerical reconstruction of the derived moments of FPK equation is introduced by coarsening the continuous state space into a discretized region of cells. Then the cell renormalized FPK (CR-FPK) equation is solved by difference method. Three numerical examples are illustrated and the effectiveness of proposed method is assessed and verified.
2018, 8(4): 245 -251.   doi: 10.1016/j.taml.2018.04.001
[Abstract] (323) [FullText HTML] (96) [PDF 2758KB] (29)
Abstract:
Numerous experimental evidences show that the grain size may significantly alter the yield strength of metals. Similarly, in \begin{document}$\gamma '$\end{document} -strengthened nickel-based superalloys, the precipitate size also influences their yield strength. Then, how to describe such two kinds of size effects on the yield strength is a very practical challenge. In this study, according to experimental observations, a collinear micro-shear-bands model is proposed to explore these size effects on metal materials’ yield strength. An analytical solution for the simple model is derived. It reveals that the yield strength is a function of average grain-size or precipitate-size, which is able to reasonably explain size effects on yield strength. The typical example validation shows that the new relationship is not only able to precisely describe the grain-size effect in some cases, but also able to theoretically address the unexplained Hall-Petch relationship between the \begin{document}$\gamma '$\end{document} precipitate size and the yield strength of nickel-based superalloys.
2018, 8(4): 252 -256.   doi: 10.1016/j.taml.2018.04.006
[Abstract] (191) [FullText HTML] (99) [PDF 2725KB] (32)
Abstract:
The bubbles rise up and burst at the free surface is a complex two-phase process. A free energy lattice Boltzmann method (LBM) model is adopted in this paper to study this phenomenon. The interface capturing technique [Zheng et al., 2006] is used to deal with the high density ratio problem. The Laplace law and the air-water interface capturing ability are validated for the multiphase model. The interaction between the single bubble or multiple bubbles and the free surface are studied by the multiphase model. The force acting on the bubble and the evolution of the free surface is studied. Meanwhile, effect of the initial distance between two adjacent bubbles on interaction effects of multiple bubbles is investigated as well.
2018, 8(4): 257 -266.   doi: 10.1016/j.taml.2018.04.004
[Abstract] (90) [FullText HTML] (50) [PDF 4047KB] (10)
Abstract:
The principle and 1:3 internal resonance of a rectangular thin plate in a transverse magnetic field is investigated. Based on the magneto-elastic vibration equation and electromagnetic force expressions of the thin plates, the nonlinear magneto-elastic vibration differential equations of rectangular plates under external excitation in a transverse magnetic field are derived. For a rectangular plate with one side fixed and three other sides simply supported, the two-degree-of-freedom nonlinear Duffing vibration differen-tial equations are proposed by the method of Galerkin. The method of multiple scales is adopted to solve the model equations and obtain four first-order ordinary differential equations governing modulation of the amplitudes and phase angles involved via the first-order or the second-order primary-internal reso-nances. With a numerical example, the amplitude frequency response curves, time history responses, phase portraits and Poincare maps of the first two order vibration modes via principle-internal resonance are respectively captured. And the effects of external excitation amplitudes, magnetic field intensities and thicknesses on the vibration of system are discussed. The results show that the response is dominated by the low mode when principle-internal resonance occurs. The internal resonance provides a mechanism for transferring energy from a high mode to a low mode.
2018, 8(4): 267 -271.   doi: 10.1016/j.taml.2018.04.005
[Abstract] (110) [FullText HTML] (53) [PDF 2686KB] (6)
Abstract:
The potential for harvesting energy from a flexible delta wing using a piezoelectric bimorph is experimentally investigated. Different configurations of the proposed harvesting system were tested in a wind tunnel over a broad range of airspeeds. In addition to evaluating the level of harvested power, an analysis is performed to extract critical aspects for the relation between speed, flexibility, geometry and the potential power that can be harvested from a clamped, cantilevered flexible delta wing at low angles of attack and low speeds. This analysis provides an insight into parameters that impact energy harvesting from flexible membranes or elements.
2018, 8(4): 272 -276.   doi: 10.1016/j.taml.2018.04.003
[Abstract] (217) [FullText HTML] (94) [PDF 2759KB] (12)
Abstract:
To reproduce the premature rupture process of metal sheet subjected to laser irradiation with subsonic airflow, which is an interesting phenomenon observed in the experiments given by Lawrence Livermore National Laboratory, a coupled numerical model considering the interaction and evolution of metal elastoplastic deformation and aerodynamic pressure profile is presented. With the thermal elastoplastic constitutive relationship and failure criterion, the simulated failure modes and dynamic rupture process are basically consistent with the experimental results, indicating plastic flow and multiple fracturing is the main failure mechanism. Compared with the case of non-airflow, subsonic airflow not only accelerates deformation, but also turns the bugle deformation, plastic strain and rupture mode into asymmetric.
2018, 8(4): 277 -283.   doi: 10.1016/j.taml.2018.04.002
[Abstract] (77) [FullText HTML] (50) [PDF 5157KB] (9)
Abstract:
Numerical simulations using volume of fluid (VOF) method are performed to study the impact of liquid-to-gas density ratio on the trajectory of nonturbulent liquid jets in gaseous crossflows. In this paper, large eddy simulation (LES) turbulence model is coupled with the VOF method to describe the turbulence effects accurately. In addition, dynamic adaptive mesh refinement method with two refinement levels is applied to refine the size of the cells located at gas-liquid interface. Density ratio is changed from 10 to 5000 while other nondimensional numbers are kept constant. Large density ratios are considered in this paper since they are common in many practical applications such as solution precursor/suspension plasma sprays. Our simulations show that the penetration height, especially in the farfield, increases as the density ratio increases. A general correlation for the jet trajectory, which can be used for a wide range of density ratios, is developed based on our simulation results.
2018, 8(4): 284 -290.   doi: 10.1016/j.taml.2018.04.007
[Abstract] (75) [FullText HTML] (45) [PDF 2915KB] (4)
Abstract:
This work focuses on the study of the effect of hydrophobicity on the water flow in carbon nanotubes (CNTs) using a molecular dynamics (MD) approach for a wide range of potential applications such as water purification and high efficiency of nanofluid energy absorption systems (NEAS). The hydrophobicity between liquid water and surface of CNTs was characterized by interaction-energy-coefficient (IEC)—a parameter describing the energy interaction strength between water molecules and carbon atoms. It is shown that the static contact angles between water and carbon surface decrease from 155° to 44° when the values of IEC increase from 0.042 kJ/mol to 2.196 kJ/mol. In addition, the pressure drops in CNT became independent of IEC when the IEC value was higher than 1.192 kJ/mol for a given flow rate. It was found that the hydrophobicity of CNT surface has a significant impact on the pressure drop of water flow in the CNTs and MD method provides a quantitative evaluation of the impact.
2018, 8(4): 291 -297.   doi: 10.1016/j.taml.2018.04.009
[Abstract] (65) [FullText HTML] (30) [PDF 3104KB] (2)
Abstract:
This paper aims to investigate the hydrodynamic behavior of a tension leg platform (TLP) when the tendon connection angles are varied at 90°, 70°, 50°, and 30°. Three different types of loading conditions are applied to the TLP. Conditions include 100-year hurricane storm period, regular waves and no loading. The TLP displayed major response in the pitch degree of freedom. A maximum reduction of 14% in pitch rotation is achieved when 100-year hurricane storm conditions are applied to the TLP. This occurred in 0° loadings at 30° tendon connection angle as compared to 90° tendon connection angle. Reduction in pitch rotation is also achieved in the regular wave loadings. A maximum of 9% in pitch rotation is achieved during 0° wave loading at 30° tendon connection angle as compared to 90°. When the tendon connection angle is reduced from 90° to 30°, the natural frequency of the TLP increased both in pitch and yaw degrees of freedom by 2.55% and 2.40%, respectively.
2018, 8(3): 153-159   doi: 10.1016/j.taml.2018.03.002
[Abstract](269) [FullText HTML](109) [PDF 4354KB](37)
2018, 8(4): 252-256   doi: 10.1016/j.taml.2018.04.006
[Abstract](191) [FullText HTML](99) [PDF 2725KB](32)
2018, 8(4): 245-251   doi: 10.1016/j.taml.2018.04.001
[Abstract](323) [FullText HTML](96) [PDF 2758KB](29)
2018, 8(3): 143-146   doi: 10.1016/j.taml.2018.03.006
[Abstract](203) [FullText HTML](105) [PDF 2524KB](22)
2018, 8(5): 299-303   doi: 10.1016/j.taml.2018.05.007
[Abstract](108) [FullText HTML](40) [PDF 3697KB](21)
2018, 8(3): 147-152   doi: 10.1016/j.taml.2018.03.001
[Abstract](156) [FullText HTML](87) [PDF 3225KB](18)
2018, 8(5): 334-344   doi: 10.1016/j.taml.2018.05.004
[Abstract](137) [FullText HTML](46) [PDF 4235KB](16)
2018, 8(4): 272-276   doi: 10.1016/j.taml.2018.04.003
[Abstract](217) [FullText HTML](94) [PDF 2759KB](12)
2018, 8(2): 137-141   doi: 10.1016/j.taml.2018.02.010
[Abstract](155) [FullText HTML](257) [PDF 2604KB](11)
2018, 8(4): 231-244   doi: 10.1016/j.taml.2018.04.008
[Abstract](204) [FullText HTML](76) [PDF 4064KB](11)