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Inlet flow disturbance effects on direct numerical simulation of incompressible round jet at Reynolds number 2500
Zejing Hu, Yongliang Zhang, Zuojin Zhu
Accepted Manuscript , doi: 10.1016/j.taml.2018.05.009
[Abstract] (1) [FullText HTML] (1) [PDF 2816KB] (1)
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 ($B_{\rm u}$) and distribution parameter ($K_{\rm u}$) for velocity profile in self-similar region.
Continuum percolation of porous media via random packing of overlapping cube-like particles
Jianjun Lin, Huisu Chen
Accepted Manuscript
[Abstract] (6) [FullText HTML] (6) [PDF 2879KB] (6)
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 $\end{document} ) for the cube-like particle systems with shape parameter s in [1.0, +∞] are derived successively. Then, based on the relation between the percolation threshold \begin{document}$\psi $\end{document} c in infinite space and the local percolation threshold \begin{document}$\psi $\end{document} c(L), the corresponding \begin{document}$\psi $\end{document} c with s in [1.0, +∞] are further determined. It is shown from the study that the characteristics of cube-like particles have significant influence on the global percolation threshold \begin{document}$\psi $\end{document} c of the particle packing systems. As the parameter s increases from 1.0 to +∞, the percolation threshold \begin{document}$\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.
Linear and Nonlinear Dynamics and Sensitivity Analysis of a Vibratory Ring Gyroscope
Dong-Dong Liang, Xiao-Dong Yang, Wei Zhang, Yuan Ren, Tianzhi Yang
Accepted Manuscript , doi: 10.1016/j.taml.2018.06.001
[Abstract] (2) [FullText HTML] (2) [PDF 3857KB] (0)
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.
The singularity in the state-based peridynamic solution of uniaxial tension
Zaixing HUANG
Accepted Manuscript , doi: 10.1016/j.taml.2018.05.008
[Abstract] (2) [FullText HTML] (2) [PDF 2381KB] (1)
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.
Intrinsic relationship of vorticity between modes A and B in the wake of a bluff body
L. M. Lin, S. Y. Shi, Y. X. Wu
Accepted Manuscript
[Abstract] (24) [FullText HTML] (6) [PDF 3261KB] (3)
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.
Pattern dynamics in telegraph reaction diffusion
Qianqian Zheng, Fang Han, Zhijie Wang
Accepted Manuscript
[Abstract] (18) [FullText HTML] (9) [PDF 3499KB] (3)
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.
A visualized study of interfacial behavior of air-water two-phase flow in a rectangular Venturi channel
Jiang Huang, Licheng Sun, Min Du, Zhengyu Mo, Liang Zhao
Accepted Manuscript
[Abstract] (16) [FullText HTML] (9) [PDF 4256KB] (3)
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.
An improved Lattice Boltzmann model for high gas and liquid density ratio in composite grids
Shaojun Zhang, Wanqing Wu, Qinggong Zheng
Accepted Manuscript , doi: 10.1016/j.taml.2018.05.003
[Abstract] (18) [FullText HTML] (10) [PDF 2721KB] (5)
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.
Air entrainment in a vertical dropshaft with limited air supply
Qiang Ding, Yiyi Ma, David Z. Zhu
Accepted Manuscript , doi: 10.1016/j.taml.2018.05.002
[Abstract] (42) [FullText HTML] (23) [PDF 2580KB] (7)
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.
Traffic flow and safety analysis
Jing Gao, Lili Dai, Xu Gan
Accepted Manuscript , doi: 10.1016/j.taml.2018.05.005
[Abstract] (18) [FullText HTML] (9) [PDF 4185KB] (2)
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.

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Estimation of the effective properties of two-dimensional cellular materials: a review
Federica Ongaro
2018, 8(4): 209 -230.   doi: 10.1016/j.taml.2018.04.010
[Abstract] (57) [FullText HTML] (25) [PDF 3780KB] (4)
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.
A data-based CR-FPK method for nonlinear structural dynamic systems
Jie Li, Zhongming Jiang
2018, 8(4): 231 -244.   doi: 10.1016/j.taml.2018.04.008
[Abstract] (134) [FullText HTML] (52) [PDF 4064KB] (11)
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.
Collinear micro-shear-bands model for grain-size and precipitate-size effects on the yield strength
Yike Qiu, Peng Zhang, Lifeng Ma
2018, 8(4): 245 -251.   doi: 10.1016/j.taml.2018.04.001
[Abstract] (278) [FullText HTML] (81) [PDF 2758KB] (26)
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.
On the interaction between bubbles and the free surface with high density ratio 3D lattice Boltzmann method
Guo-Qing Chen, A-Man Zhang, Xiao Huang
2018, 8(4): 252 -256.   doi: 10.1016/j.taml.2018.04.006
[Abstract] (120) [FullText HTML] (76) [PDF 2725KB] (27)
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.
Principal and internal resonance of rectangular conductive thin plate in transverse magnetic field
Jing Li, Yuda Hu
2018, 8(4): 257 -266.   doi: 10.1016/j.taml.2018.04.004
[Abstract] (60) [FullText HTML] (37) [PDF 8005KB] (9)
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.
Piezoelectric energy harvesting from flexible delta wings
Jamal S. Alrowaijeh, Muhammad R. Hajj
2018, 8(4): 267 -271.   doi: 10.1016/j.taml.2018.04.005
[Abstract] (73) [FullText HTML] (35) [PDF 2675KB] (6)
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.
Dynamic rupture of metal sheet subjected to laser irradiation and tangential subsonic airflow
Xiaodong Xing, Te Ma, Ruixing Wang, Chenyu Cao, Hongwei Song, Chenguang Huang
2018, 8(4): 272 -276.   doi: 10.1016/j.taml.2018.04.003
[Abstract] (185) [FullText HTML] (80) [PDF 2759KB] (10)
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.
On the trajectory of nonturbulent liquid jets in subsonic crossflows at different density ratios
Mehdi Jadidi, Ali Dolatabadi
2018, 8(4): 277 -283.   doi: 10.1016/j.taml.2018.04.002
[Abstract] (53) [FullText HTML] (34) [PDF 5157KB] (8)
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.
Effect of hydrophobicity on the water flow in carbon nanotube—A molecular dynamics study
Hamed Esmaeilzadeh, Junwei Su, Majid Charmchi, Hongwei Sun
2018, 8(4): 284 -290.   doi: 10.1016/j.taml.2018.04.007
[Abstract] (47) [FullText HTML] (31) [PDF 2915KB] (3)
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.
Investigation of TLP's hydrodynamic response with different tendon connection angles
Yang Yu, Aaron Hardowar, Jianxing Yu, Shuai Hao, Xiaodong Gao
2018, 8(4): 291 -297.   doi: 10.1016/j.taml.2018.04.009
[Abstract] (27) [FullText HTML] (12) [PDF 3104KB] (2)
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.
Effects of tide-surge interaction and wave set-up/set-down on surge: case studies of tropical cyclones landing China's Zhe-Min coast
Qingyong Wuxi, Jiachun Li, Bingchuan Nie
2018, 8(3): 153-159   doi: 10.1016/j.taml.2018.03.002
[Abstract](214) [FullText HTML](92) [PDF 4354KB](33)
On the interaction between bubbles and the free surface with high density ratio 3D lattice Boltzmann method
Guo-Qing Chen, A-Man Zhang, Xiao Huang
2018, 8(4): 252-256   doi: 10.1016/j.taml.2018.04.006
[Abstract](120) [FullText HTML](76) [PDF 2725KB](27)
Collinear micro-shear-bands model for grain-size and precipitate-size effects on the yield strength
Yike Qiu, Peng Zhang, Lifeng Ma
2018, 8(4): 245-251   doi: 10.1016/j.taml.2018.04.001
[Abstract](278) [FullText HTML](81) [PDF 2758KB](26)
Rational subgrid-scale modelling: a short survey
L. Fang, L.P. Lu
2018, 8(3): 143-146   doi: 10.1016/j.taml.2018.03.006
[Abstract](160) [FullText HTML](89) [PDF 2524KB](22)
Rowing jellyfish contract to maintain neutral buoyancy
Patricia J. Yang, Matthew Lemons, David L. Hu
2018, 8(3): 147-152   doi: 10.1016/j.taml.2018.03.001
[Abstract](137) [FullText HTML](76) [PDF 3225KB](17)
A data-based CR-FPK method for nonlinear structural dynamic systems
Jie Li, Zhongming Jiang
2018, 8(4): 231-244   doi: 10.1016/j.taml.2018.04.008
[Abstract](134) [FullText HTML](52) [PDF 4064KB](11)
Dynamic rupture of metal sheet subjected to laser irradiation and tangential subsonic airflow
Xiaodong Xing, Te Ma, Ruixing Wang, Chenyu Cao, Hongwei Song, Chenguang Huang
2018, 8(4): 272-276   doi: 10.1016/j.taml.2018.04.003
[Abstract](185) [FullText HTML](80) [PDF 2759KB](10)
A three-dimensional immersed boundary method for non-Newtonian fluids
Luoding Zhu
2018, 8(3): 193-196   doi: 10.1016/j.taml.2018.03.008
[Abstract](135) [FullText HTML](53) [PDF 2523KB](10)
A new equivalent method to obtain the stoichiometric fuel-air cloud from the inhomogeneous cloud based on FLACS-dispersion
Yulong Zhang, Yuxin Cao, Lizhi Ren, Xuesheng Liu
2018, 8(2): 109-114   doi: 10.1016/j.taml.2018.02.006
[Abstract](136) [FullText HTML](152) [PDF 3161KB](10)
An improved wall shear stress measurement technique using sandwiched hot-film sensors
Xuanhe Liu, Zhuoyue Li, Nan Gao
2018, 8(2): 137-141   doi: 10.1016/j.taml.2018.02.010
[Abstract](123) [FullText HTML](237) [PDF 2604KB](10)