A comparative study of interface reconstruction algorithms in molten metal flow

In the present research,two numerical schemes for improving the accuracy of the solution in the flow simulation of molten metal were applied.One method is the Piecewise Linear Interface Calculation(PLIC) method and the other is the Donor-Acceptor(D-A) method.To verify the module of the interface reconstruction algorithms,simple problems were tested.After these validations,the accuracy and efficiency of these two methods were compared by simulating various real products.On the numerical simulation of free surface flow,it is possible for the PLIC method to track very accurately the interface between phases.The PLIC method,however,has the weak point in that a lot of computational time is required,though it shows the more accurate interface reconstruction.The Donor-Acceptor method has enough effectiveness in the macro-observation of a mold filling sequence though it shows inferior accuracy.Therefore,for the problems that need the accurate solution,PLIC is more appropriate than D-A.More accuracy may cause less efficiency in numerical analysis.Which method between D-A method and PLIC method should be chosen depends on the product.

A 2D Staggered Multi-Material ALE Code Using MOF Interface Reconstruction

Hydrocodes are necessary numerical tools in the fields of implosion and high-velocity impact,which often involve large deformations with changing-topology interfaces.It is very difficult for Lagrangian or Simplified Arbitrary Lagrangian-Eulerian(SALE)codes to tackle these kinds of large-deformation problems,so a stag-gered Multi-Material ALE(MMALE)code is developed in this paper,which is the explicit time-marching Lagrange plus remap type.We use the Moment Of Fluid(MOF)method to reconstruct the interfaces of multi-material cells and present an adaptive bisection method to search for the global minimum value of the nonlinear objective function.To keep the Lagrangian computations as long as possible,we develop a ro-bust rezoning method named as Combined Rezoning Method(CRM)to generate the convex,smooth grids for the large-deformation domain.Regarding the staggered remap phase,we use two methods to remap the variables of Lagrangian mesh to the rezoned one.One is the first-order intersection-based remapping method that doesn’t limit the distances between the rezoned and Lagrangian meshes,so it can be used in the applications of wide scope.The other one is the conservative second-order flux-based remapping method developed by Kucharika and Shashkov[22]that requires the rezoned element to locate in its adjacent old elements.Numerical results of triple point problem show that the result of first-order remapping method using ALE computations is gradually convergent to that of second-order remapping method using Eulerian computations with the decrease of rezoning,thereby telling us that MMALE computations should be performed as few as possible to reduce the errors of the interface reconstruction and the remapping.Numerical results provide a clear evidence of the robustness and the accuracy of this MMALE scheme,and that our MMALE code is powerful for the large-deformation problems.

Facile construction of a multilayered interface for a durable lithium‐rich cathode

Layered lithium-rich manganese-based oxide(LRMO)has the limitation of inevitable evolution of lattice oxygen release and layered structure transformation.Herein,a multilayer reconstruction strategy is applied to LRMO via facile pyrolysis of potassium Prussian blue.The multilayer interface is visually observed using an atomic-resolution scanning transmission electron microscope and a high-resolution transmission electron microscope.Combined with the electrochemical characterization,the redox of lattice oxygen is suppressed during the initial charging.In situ X-ray diffraction and the high-resolution transmission electron microscope demonstrate that the suppressed evolution of lattice oxygen eliminates the variation in the unit cell parameters during initial(de)lithiation,which further prevents lattice distortion during long cycling.As a result,the initial Coulombic efficiency of the modified LRMO is up to 87.31%,and the rate capacity and long-term cycle stability also improved considerably.In this work,a facile surface reconstruction strategy is used to suppress vigorous anionic redox,which is expected to stimulate material design in high-performance lithium ion batteries.

Understanding solid phase diffusion-bonding process of Ni(000)/-Al_(2)O_(3)(0001) interface

The dynamic processes and characteristics of solid phase diffusion-bonding of interfacial atoms at high tempera-tures and the effect of that on bonding strength of Ni(111)/)/-Al_(2)O_(3)(0001)interface were investigated through molecular dynamics.It is shown that atomic diffusion occurs at the Ni/Al_(2)O_(3) interface in the temperature range from 698 K to 1,098 K,and proceeds mainly from the Ni side to the ) Al_(2)O_(3) side.The interface was previously reconstructed by solid bonding below the melting temperature,leading to the amorphization of the interface.Be-sides,the intermetallic complexes such as Al_(m)Ni_(n)(e.g.,AlNi_(3)),metal oxide NiO and Ni-Al-O bonds were formed gradually during the diffusion process of atoms.The formation mechanisms of the Ni-Al,Ni-O,and Ni-Al-O bonds are revealed.Based on the reconstructed structure,the adhesion effort at the interface is compared.The higher the temperature,the larger the bond number and the higher the interfacial bonding strength.

Partial aging can counter-intuitively couple with sulfidation to improve the reactive durability of zerovalent iron

Sulfated zero-valent iron(SZVI)has shown promising applications in wastewater treatment.However,the rapid decline in the reactivity of SZVI with time limits its real practice.To mediate this problem,partial aging was proposed to improve the reactive durability of SZVI.Taking Cr(VI)as the target contaminant,we found that the aged ZVI(AZVI)gradually lost reactivity as aging time increased from 0.5 to 2 d.Counter-intuitively,the partially aged SZVI(ASZVI)showed greater reactivity than SZVI when exposed to oxygenated water for a period ranging from 0.5 to 14 d.In addition,the ASZVI with 0.5 d of aging time(ASZVI-0.5)not only maintained reactivity in successive runs but also increased the Cr(VI)removal capacity from 9.1 mg/g by SZVI to 19.1 mg/g by ASZVI-0.5.Correlation analysis further revealed that the electron transfer from the Fe0 core to the shell was mediated by the conductive FeS and FeS2 in the subshell of ASZVI.Meanwhile,the lepidocrocite and magnetite on the surface of ASZVI facilitated Cr(VI)adsorption and subsequent electron transfer for Cr(VI)reduction.Moreover,the iron(hydr)oxide shell could retain the conductive FeS and FeS2 in the subshell,allowing ASZVI to reduce Cr(VI)efficiently and sustainably.In general,partial aging can enhance the reactive durability of ZVI when coupled with sulfidation and this synergistic effect will be beneficial to the application of SZVI-based technology for wastewater treatment.

Three-dimensional bioprinting biphasic multicellular living scaffold facilitates osteochondral defect regeneration

Due to tissue lineage variances and the anisotropic physiological character-istics,regenerating complex osteochondral tissues(cartilage and subchondral bone)remains a great challenge,which is primarily due to the distinct requirements for cartilage and subchondral bone regeneration.For cartilage regeneration,a significant amount of newly generated chondrocytes is required while maintaining their phenotype.Conversely,bone regeneration necessitates inducing stem cells to differentiate into osteoblasts.Additionally,the construction of the osteochondral interface is crucial.In this study,we fabricated a biphasic multicellular bioprinted scaffold mimicking natural osteochondral tissue employing three-dimensional(3D)bioprinting technol-ogy.Briefly,gelatin-methacryloyl(GelMA)loaded with articular chondrocytes and bone marrow mesenchymal stem cells(ACs/BMSCs),serving as the cartilage layer,preserved the phenotype of ACs and promoted the differentia-tion of BMSCs into chondrocytes through the interaction between ACs and BMSCs,thereby facilitating cartilage regeneration.GelMA/strontium-substituted xonotlite(Sr-CSH)loaded with BMSCs,serving as the subchondral bone layer,regulated the differentiation of BMSCs into osteoblasts and enhanced the secretion of cartilage matrix by ACs in the cartilage layer through the slow release of bioactive ions from Sr-CSH.Additionally,GelMA,serving as the matrix material,contributed to the reconstruction of the osteochondral interface.Ultimately,this biphasic multicellular bioprinted scaffold demonstrated satisfactory simultaneous regeneration of osteochondral defects.In this study,a promising strategy for the application of 3D bioprinting technology in complex tissue regeneration was proposed.

A radial basis function for reconstructing complex immersed boundaries in ghost cell method

It is important to track and reconstruct the complex immersed boundaries for simulating fluid structure interaction problems in an immersed boundary method（IBM）. In this paper, a polynomial radial basis function（PRBF） method is introduced to the ghost cell immersed boundary method for tracking and reconstructing the complex moving boundaries. The body surfaces are fitted with a finite set of sampling points by the PRBF, which is flexible and accurate. The complex or multiple boundaries could be easily represented. A simple treatment is used for identifying the position information about the interfaces on the background grid. Our solver and interface reconstruction method are validated by the case of a cylinder oscillating in the fluid. The accuracy of the present PRBF method is comparable to the analytic function method. In ta flow around an airfoil, the capacity of the proposed method for complex geometries is well demonstrated.

A Multi-Material CCALE-MOF Approach in Cylindrical Geometry

In this paper we present recent developments concerning a Cell-Centered Arbitrary Lagrangian Eulerian(CCALE)strategy using the Moment Of Fluid(MOF)interface reconstruction for the numerical simulation of multi-material compressible fluid flows on unstructured grids in cylindrical geometries.Especially,our attention is focused here on the following points.First,we propose a new formulation of the scheme used during the Lagrangian phase in the particular case of axisymmetric geometries.Then,the MOF method is considered for multi-interface reconstruction in cylindrical geometry.Subsequently,a method devoted to the rezoning of polar meshes is detailed.Finally,a generalization of the hybrid remapping to cylindrical geometries is presented.These explorations are validated by mean of several test cases using unstructured grid that clearly illustrate the robustness and accuracy of the new method.

ON THE VOLUME OF FLUID METHOD FOR MULTIPHASE FLUID FLOW SIMULATION

Numerical study of multiphase fluid flows require mathematical methods for distinguishing interface between two fluids.The volume of fluid(VOF)method is one of such method which takes care of fluid shape in a local domain and reconstructs the interface from volume fraction of one fluid.Maintaining sharp interface during reconstruction is a challenging task and geometrical approach of VOF method better suits for incompressible fluids.This paper provides a complete mathematical discussion of extended form of VOF method using a approach known as piecewise linear interface calculation(PLIC).An analytical relation between volume fraction and interface position has been explored with the help of primitive geometrical shapes.The method with this analytical relation has been applied to multiphase fluid flow benchmark problems and found to be in good agreement.