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Research on vacuum drying process and internal heat conduction of Li-ion battery core

Zhao Jiang, Fanghua Zhao, Yuming Guan, Zizhen Qiu

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.008

[Abstract] (1) [FullText HTML] (0) [PDF 0KB] (0)

Abstract:
In this research, an innovative cylindrical automatic battery core oven was designed to avoid the structural deformation that frequently occurs in traditional ovens. The oven could be automatically connected with the electrolyte injection process after baking, achieving improvement in a battery's baking consistency. This contributed to the feasibility of studying the internal heat conduction process of batch battery cores during actual baking processes. A mathematical model of a certain plate battery cell during the baking process was established. The simulation results of the temperature change inside the battery core during the baking process were consistent with the calculation results of the mathematical model. The temperature distribution at each point inside the battery core could be fitted through the thermal conductivity at different temperatures and the temperature distribution between the layers of the battery core. Finally, based on the thermodynamic balance energy conservation method, the relationship between the temperature change inside the battery core and the entire baking process was established. A feasible algorithm for studying the thermal conduction of complex material and internal structure objects in the baking process was obtained.

Particle selectivity of filtering by C. elegans

Yuki Suzuki, Kenji Kikuchi, Keiko Tsuruta-Numayama, Takuji Ishikawa

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.001

[Abstract] (1) [FullText HTML] (0) [PDF 0KB] (0)

Abstract:
A nematode Caenorhabditis elegans (C. elegans) is a filter feeder, which draws a suspension of bacteria and separates bacteria from the solvent by using pharyngeal pumping motions and specific mouth parts. This mechanism has not been fully understood. We investigated the mechanism of filtering of bacteria in the pharynx of C. elegans by visualization by fluorescent particles and dyed E. coli. We succeeded in quantifying the selectivity of bacteria-sized particles by C. elegans. The most accumulated particles were those of 0.5 μm in diameter. The quantity of accumulated particles of 0.2 μm or 1.0 μm in diameter was about one third of that of particles of 0.5 μm in diameter. The least accumulated particles were those of 0.05 μm in diameter. These results suggest that the pharyngeal structures of C. elegans would be suitable for eating bacteria because the size of bacteria ingested by C. elegans worms is about 0.5 μm in diameter. We also succeeded in visualizing pharyngeal structures and pumping motions and flow in the pharynx. We found that there were phase differences in the motions among procorpus, metacorpus and isthmus. This result suggests filtering would occur at the two tips of procorpus and isthmus by the phase differences. We found that bacteria-sized particles and bacteria were flowed and trapped in the channels, which existed along the central lumen from tip of procorpus to isthmus. From our results, we proposed the novel mechanism of filtering of bacteria through the channels for flowing and trapping. In future, this selective filtering mechanism of C. elegans would be applied to development of microfluidic filtration devices for medical and biological equipment.

Air-vent layouts and water-air flow behaviors of a wide spillway aerator

James Yang, Penghua Teng, Chang Lin

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.009

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Abstract:
A spillway aerator should guarantee favorable flow conditions in the coupled water-air system even if the aerator is unconventionally wide. Eight air-vent configurations are devised and incorporated into a 35-m wide chute aerator for a generalized study. Computational fluid dynamics (CFD) simulations are performed to explore their effects on water-jet and air-cavity features. The Re-normalisation group (RNG)

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turbulence model and the two-fluid model are combined to predict the two-phase flow field. The results demonstrate appreciable influences of the vent layouts on the water-air flow. The air vents stir the air motion and re-distribute the cavity air pressure. Once the vent layout is modified, reciprocal adjustments exist between the jet behavior and air-pressure field in the cavity, thus leading to considerable differences in air-flow rate, jet-trajectory length, vent air-flow distribution across the chute, etc. The large width plays a discernable role in affecting the aerated flow. Telling differences exist between the near-wall region and the central part of the chute. To improve the duct pressure propagation, a gradual augment of the vent area should be assigned towards the chute center. Relative to single-slot vents across the flow, the layouts with segregated vents gain by comparison. A designer should see to it that a vented aerator operates satisfactorily for a given range of flow discharges.

Impact of spray droplets on momentum and heat transport in a turbulent marine atmospheric boundary layer

Ming Pan, Caixi Liu, Qingxiang Li, Shuai Tang, Lian Shen, Yuhong Dong

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.002

[Abstract] (29) [FullText HTML] (8) [PDF 2828KB] (3)

Abstract:
Droplet-laden turbulent airflow (i.e. the mixture of dry air and water vapor) in the marine atmospheric boundary layer is described by an open channel flow configuration in direct numerical simulation (DNS). The dispersed phase, the spray droplets are tracked in a Lagrangian framework, and their impact on the carrier airflow is modeled with the two-way coupling between the two phases. A wide-range droplet size is typically found near the air–sea interface according to the sea spray concentration function (SSCF). The interactions of the droplets with turbulent airflow including mass, momentum, and energy exchange are investigated here. We found a balancing mechanism exists in the droplet effects on the turbulent drag coefficient, since spray droplets lead to a decreased vertical turbulent momentum transport, but also lead to an increased droplet contribution to total drag coefficient. For the heat transfer, as droplet mass loading increasing, the total Nusselt number decreases due to the depression of turbulent heat flux and enhanced negative droplet convective flux.

Marangoni liquid film scattering over an extending cylinder

Taza Gul, M. Sohail

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.006

[Abstract] (28) [FullText HTML] (10) [PDF 3026KB] (2)

Abstract:
The impact of the Marangoni convection over the thin film flow on an expanding cylinder has been examined in this study. The diverse effect of the embedded constraints has been detected during the liquid film flow. It has been examined that the behavior of the physical parameters altered after the small intervals and diverse from the traditional approach. The similarity variables have been utilized to alter the basic flow equations into the nonlinear ordinary differential equations. The result of the transformed equations is computed by BVPh 2.0 package. The performance of different constraints, for flow motion and temperature distributions are plotted and conferred. It has been observed that under the Marangoni convection the impact of the physical parameters varies after the point of inflection and the diverse impact of the embedding constraints provide space for the variation of the point of inflection for the desired spray analysis.

A new numerical framework for large-eddy simulation of waves generated by objects piercing water surface

Zixuan Yang, Zuo Cui, Shizhao Wang

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.003

[Abstract] (65) [FullText HTML] (24) [PDF 2560KB] (3)

Abstract:
A novel numerical framework is developed for large-eddy simulation (LES) of interactions among air, water, and solid bodies. The motions of air and water are solved on a fixed block-structured mesh, with the air–water interface captured using the volume-of-fluid method. A new sub-grid scale stress model based on the vortex identifier is used to improve the robustness and efficiency of the simulation flows with air–water interface. The new framework is tested in the context of bow waves and Kelvin waves generated by a water-surface vehicle. Wave breaking at the bow of the vehicle is captured in LES. The LES results of wave geometry approaches the measurements progressively as the grid resolution is refined. The simulation results indicate that LES is a useful tool for studying wave dynamics of water-surface vehicles.

The extractable hydrokinetic power from an oscillating membrane-based harvester

Francisco J. Arias, Salvador De Las Heras

Accepted Manuscript , doi: 10.1016/j.taml.2019.01.003

[Abstract] (50) [FullText HTML] (24) [PDF 2579KB] (3)

Abstract:
The extractable hydrokinetic power from an oscillating membrane in standing motion and induced by a water flow and its possible significance with regard energy harvesting is discussed. The main attractiveness of such an energy harvester lies in the possibility of an inexpensive technology able to be used in those water flows which either because limitation of space (narrow channels) or a limited differential pressure drop with the surrounding but yet with a non negligible velocity are not well suited to be turbined. Utilizing a simplified geometrical model, an estimate of the extractable output density power per area of membrane was derived. Preliminary experiments were performed using a rectangular thin rubber membrane and for a typical domestic water intake as source. The experimental data quantitatively agree very well with the theoretical prediction where it was found that for water flows around 2m/s the output power density from the membrane may be around 30 mW/cm² of membrane. Additional research and development is required in order to arrive at a reliable practical and commercial design.

On the thixotropic effect of turbulence

Yu-Ning Huang

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.007

[Abstract] (44) [FullText HTML] (17) [PDF 2493KB] (9)

Abstract:
As a follow-up research of the work on the natural viscosity of turbulence of Huang et al. [Journal of Turbulence (2003)], here we investigate the thixotropic effect of a turbulent Newtonian fluid on the basis of the ensemble-averaged Navier–Stokes equation. In view of the natural viscosity, we show that in homogeneous isotropic turbulence the turbulent Newtonian fluid behaves like a thixotropic fluid, exhibiting the thixotropic effect with its natural viscosity decreasing with time.

Numerical solutions for point masses sliding over analytical surfaces: Part 2

Stefano Tinti, Glauco Gallotti

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.005

[Abstract] (22) [FullText HTML] (8) [PDF 3031KB] (2)

Abstract:
This paper is the second of two companion papers addressing the dynamics of two coupled masses sliding on analytical surfaces and interacting with one another. The motion occurs under the effect of gravity, the reaction force of the surface and basal friction. The interaction force maintains the masses at a fixed distance and lies on the line connecting them. The equations of motion form a system of ordinary differential equations that are solved through a fourth-order Runge–Kutta numerical scheme. In the first paper we considered an approximate method holding when the line joining the masses is almost tangent to the surface at the instant mass positions. In this second paper we provide a general solution. Firstly, we present special cases in which the system has exact solutions. Second, we consider a series of numerical examples where the interest is focused on the trajectories of the masses and on the intensity and changes of the interaction force.

Numerical solutions for point masses sliding over analytical surfaces: Part 1

Glauco Gallotti, Stefano Tinti

Accepted Manuscript , doi: 10.1016/j.taml.2019.02.004

[Abstract] (5) [FullText HTML] (3) [PDF 3304KB] (0)

Abstract:
In this study, we introduce a system of differential equations describing the motion of a single point mass or of two interacting point masses on a surface, that is solved by a fourth-order explicit Runge–Kutta (RK4) scheme. The forces acting on the masses are gravity, the reaction force of the surface, friction, and, in case of two masses, their mutual interaction force. This latter is introduced by imposing that the geometrical distance between the coupled masses is constant. The solution is computed under the assumption that the point masses strictly slide on the surface, without leaping or rolling. To avoid complications stemming from numerical errors related to real topographies that are only known over discrete grids, we restrict our attention to simulations on analytical continuous surfaces. This study sets the basis for a generalization to more complex systems of masses, such as chains or matrices of blocks that are often used to model complex processes such as landslides and rockfalls. The results shown in this paper provide a background for a companion paper in which the system of equations is generalized, and different geometries are presented.

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Letter

Lattice Boltzmann model of percutaneous drug absorption

Arman Safdari, Kyung Chun Kim

2019, 9(1): 1 -6. doi: 10.1016/j.taml.2019.01.008

[Abstract] (85) [FullText HTML] (37) [PDF 2883KB] (4)

Abstract:
A lattice Boltzmann numerical modeling method was developed to predict skin concentration after topical application of a drug on the skin. The method is based on D2Q9 lattice spaces associated with the Bhatnagar-Gross-Krook (BGK) collision term to solve the convection-diffusion equation (CDE). A simulation was carried out in different ranges of the value of bound

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, which is related to skin capillary clearance and the volume of diffusion during a percutaneous absorption process. When a typical drug is used on the skin, the value of

\begin{document}$\gamma $\end{document}

corresponds to the amount of drug absorbed by the blood and the absorption of the drug added to the skin. The effect of

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was studied for when the region of skin contact is a line segment on the skin surface.

Seepage-stress coupled modeling for rainfall induced loess landslide

Danyang Zhou, Zhen Zhang, Jiachun Li, Xiaoliang Wang

2019, 9(1): 7 -13. doi: 10.1016/j.taml.2019.02.006

[Abstract] (64) [FullText HTML] (28) [PDF 2890KB] (3)

Abstract:
Although rainfall is rare on the Loess Plateau of western China, landslides occur frequently there in rainy season. Surveys report that landslide hazards always follow heavy rains. In this study, a seepage-stress coupling model for rainfall induced landslide is used to examine an actual disastrous event in Yulin by the end of July, 2017. The effects of rainfall duration, rainfall intensity and soil weakening on slope stability are studied in detail. The results illustrate that the safety factor drops sharply at first and then is gradually declining to below 1.05 during additional two days of heavy rain. With soil strength softening considered, the slope would be more unstable, in which the weakening in soil cohesion is found to be a more sensitive factor.

Dependency of gamma oscillations in E/I neuronal network on illumination contrast of external stimulus

Xiaochun Gu, Fang Han, Zhijie Wang, Xia Peng

2019, 9(1): 14 -20. doi: 10.1016/j.taml.2019.01.001

[Abstract] (76) [FullText HTML] (34) [PDF 3044KB] (1)

Abstract:
Synchronous gamma oscillations are believed to play a prominent role in the information processing of biological neural systems. Experimental observations have found that the frequency and power of gamma oscillations in the primary visual cortex (V1 zone) are regulated by the illumination contrast of visual stimulus. However, the underlying mechanism of how the synchronous oscillations depend on the illumination contrast has not been well explained. We propose a local excitatory/inhibitory (E/I) neuronal network of integrate-and-fire (IAF) neurons with the difference-of-Gaussians (DOG) receptive field to unveil this mechanism. Simulation results demonstrate that the higher the illumination contrast, the higher the frequency of gamma oscillations. The power of gamma oscillations also increases with the increase of illumination contrast. These results are consistent with the experimental findings.

An energy approach to predict electromigration induced grain rotation under high current density

Yuexing Wang, Yao Yao

2019, 9(1): 21 -26. doi: 10.1016/j.taml.2019.01.002

[Abstract] (76) [FullText HTML] (49) [PDF 2643KB] (2)

Abstract:
An energy approach is proposed to describe the electromigration induced grain rotation under high current density. The driving force is assumed to arise from the grain-boundary energy reduction and increase of the inner energy from the joule heating. Energy dissipates by the grain boundary diffusion under electromigration and viscous boundary sliding is considered. Based on the conservation of energy production and dissipation, an equilibrium equation is developed to predict the grain rotation rate analytically. It is recognized that the grain rotates with the reducing of electrical resistivity and inversely proportional to the grain length. The theoretical prediction is compared with the experimental data, which shows good accuracy on the rotation trend and the specific rotation rate.

Optimal control of a mobile robot on sphere

Huageng Liu, Donghua Shi

2019, 9(1): 27 -31. doi: 10.1016/j.taml.2019.01.004

[Abstract] (103) [FullText HTML] (28) [PDF 3169KB] (8)

Abstract:
For the purpose of solving optimal control problem of a wall-crawling mobile robot working on spherical containers, we propose the Hamel's formalism for Pontryagin Maximum Principle, which gives a general framework for the optimal control of a mechanical system with velocity constraints, especially nonholonomic constraints. The effectiveness of the proposed framework is shown by the simulations for the above problem.

Key structure in laminar-turbulent transition of boundary layer with streaky structures

Joe Yoshikawa, Yu Nishio, Seiichiro Izawa, Yu Fukunishi

2019, 9(1): 32 -35. doi: 10.1016/j.taml.2019.01.005

[Abstract] (87) [FullText HTML] (43) [PDF 2657KB] (8)

Abstract:
A numerical simulation is performed to find out a key vortical structure in the laminar-turbulent transition. A low-speed streak is generated inside a laminar boundary layer using an isolated cuboid roughness, aimed at providing an environment unstable to outer disturbances. Then, a short duration jet is issued into the boundary layer. When the jet velocity is low, some vortices appear in the boundary layer, but the transition of the boundary layer does not take place. However, when the jet velocity exceeds a certain threshold, two vortices newly appear above the elongated legs of a V-shaped vortex and only one of them is stretched and survives. After that, vortices are generated one after another around the survived one. By comparing the decayed and the survived vortices, it is found that the difference in their heights is the key characteristic which leads to the transition.

Electrokinetic flow in the U-shaped micro-nanochannels

Bilong Qiu, Lingyan Gong, Zirui Li, Jongyoon Han

2019, 9(1): 36 -42. doi: 10.1016/j.taml.2019.01.006

[Abstract] (73) [FullText HTML] (27) [PDF 2920KB] (3)

Abstract:
U-shaped micro-nanochannels can generate significant flow disturbance as well as locally amplified electric field, which gives itself potential to be microfluidic mixers, electrokinetic pumps, and even cell lysis process. Numerical simulation is utilized in this work to study the hidden characteristics of the U-shaped micro-nanochannel system, and the effects of key controlling parameters (the external voltage and pressure) on the device output metrics (current, maximum values of electric field, shear stress and flow velocity) were evaluated. A large portion of current flowing through the whole system goes through the nanochannels, rather than the middle part of the microchannel, with its value increasing linearly with the increase of voltage. Due to the local ion depletion near micro-nanofluidic junction, significantly enhanced electric field (as much as 15 fold at V=1 V and P₀=0) as well as strong shear stress (leading to electrokinetic flow) is generated. With increasing external pressure, both electric field and shear stress can be increased initially (due to shortening of depletion region length), but are suppressed eventually at higher pressure due to the destruction of ion depletion layer. Insights gained from this study could be useful for designing nonlinear electrokinetic pumps and other systems.

Article

Effects of interfacial discontinuity on the fracture behavior in the superconductor-substrate system

Lang Jiang, Xiaoqiang Ren, Zhiwen Gao, Youhe Zhou

2019, 9(1): 43 -49. doi: 10.1016/j.taml.2019.01.009

[Abstract] (64) [FullText HTML] (33) [PDF 3321KB] (3)

Abstract:
This study concerns a two-dimensional model and the corresponding virtual crack closure technique (VCCT) implemented to solve the general boundary value problems that may explain why interface discontinuity has effects on the fracture behavior in the superconductor-substrate system. The interfacial discontinuity can be classified according to the material properties' continuity and their derivatives' continuity at the interface. For nonhomogeneous superconductor and substrate specimens with various material properties, a VCCT method is developed to calculate their fracture behavior. Furthermore, the effects of applied magnetic field amplitude and nonhomogeneous parameters are extensively and parametrically studied in two activation processes (zero-field cooling and field cooling). The integrative and computational study presented here provide a fundamental mechanistic understanding of the fracture mechanism in the superconductor-substrate system and sheds light on the rational design of interfacial continuity.

Article

Investigation on structural component behaviours of double bottom arrangement under grounding accidents

Aditya Rio Prabowo, Teguh Muttaqie, Jung Min Sohn, Bangun I.R. Harsritanto

2019, 9(1): 50 -59. doi: 10.1016/j.taml.2019.01.010

[Abstract] (56) [FullText HTML] (29) [PDF 3620KB] (5)

Abstract:
Marine accidents have caused immense casualties on various parties in shipping and shipbuilding industries, including financial and structural losses. This situation makes ship accident becomes a critical subject in naval architecture and marine structures, as it needs continuous assessment and investigation to broaden insight and data of collision and grounding phenomena. The paper aims to investigate structural conditions of a ship arranged by double hull system under accidental scenario, namely ship grounding. Fundamental concept of structure-rock interaction in powered-hard grounding is adopted to design impact configuration for calculation using finite element (FE) simulation. Involved entities are defined as the structure represented by tanker vessel, and oceanic rock is deployed as the indenter in analysis. Calculation results indicate that the crashworthiness capability of structural part strengthened by longitudinal girder is higher than other selected locations on the structures against rock penetration. Localized flooding of storage oil may occur during raking damage is formed on structural part between two girders.