A NEW TREATMENT FOR INTERFACE OF METAL AND DIELECTRIC IN FDTD METHOD

A new treatment for interface of metal and dielectric in finite-difference time domain (FDTD) method was presented, further how and why this treatment should be as it is was explained. The FDTD method was developed to compute the low-frequency electromagnetic fields in the metal instead of the traditional high-frequency ones as it was originally proposed. The computational results agreed well with the experimental ones.

Numerical simulation for explosion wave propagation of combustible mixture gas

A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code,Young's technique was employed to track the interface between the explosion products and air,and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct,for point initiation,the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall,multi-peak values appear on pressure-time curve,and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct,explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products,and indicate that the ignition model and multi-material interface treatment method are feasible.

A Numerical Model for Simulating Two-Phase Flow with Adaptive Mesh Refinement

In this study,a numerical model for simulating two-phase flow is developed.The Cartesian grid with Adaptive Mesh Refinement(AMR)is adopted to reduce the computational cost.An explicit projection method is used for the time integration and the Finite Difference Method(FDM)is applied on a staggered grid for the discretization of spatial derivatives.The Volume of Fluid(VOF)method with Piecewise-Linear Interface Calculation(PLIC)is extended to the AMR grid to capture the gas-water interface accurately.A coarse-fine interface treatment method is developed to preserve the flux conservation at the interfaces.Several two-dimensional(2D)and three-dimensional(3D)benchmark cases are carried out for the validation of the model.2D and 3D shear flow tests are conducted to validate the extension of the VOF method to the AMR grid.A 2D linear sloshing case is considered in which the model is proved to have 2nd-order accuracy in space.The efficiency of applying the AMR grid is discussed with a nonlinear sloshing problem.Finally,2D solitary wave past stage and 2D/3D dam break are simulated to demonstrate that the model is able to simulate violent interface problems.

Mechanical Properties and Interfacial Interaction of Modified Calcium Sulfate Whisker]Poly(Vinyl Chloride)Composites

Calcium sulfate whiskers（CSWs） modified with glutaraldehyde-crosslinked poly（vinyl alcohol）（PVA） or traditional surface modifiers,including silane coupling agent,titanate coupling agent and stearic acid,were used to strengthen poly（vinyl chloride）（PVC）,and the morphologies,mechanical and heat resistant properties of the resulting composites were compared.The results clearly show that glutaraldehyde cross-linked PVA modified CSW/PVC composite（c PVA@CSW/PVC） has the strongest interfacial interaction,good and stable mechanical and heat resistant properties.Nielsen＇s modified Kerner＇s equation for Young＇s modulus is better than other models examined for the CSW/PVC composites.The half debonding angle θ of c PVA@CSW/PVC composite is lower than that of other composites except silane coupling agent modified CSW/PVC composites,indicating a very strong interfacial adhesion between c PVA@CSW and PVC.In general,cross-linked PVA is effective and environmentally friendly in modifying inorganic fillers.

Electrodeposition of nanostructured Ti/(Ru+Ti+Ce)O_2 coatings

A nanostructured ternary coating of Ti/（Ru ＋ Ti ＋ Ce）O2 was prepared by the conventional electrodeposition on the titanium substrate as the cathode with different numbers of coating layers. The main objective of this work was to study nanostructured coatings of ceramic materials. For this purpose, the amount of precursor materials in the electrolyte was a variable parameter. Furthermore, the salt of TiCl4/RuCl3·xH2 O/Ce（NO3）3·6 H2 O with different amounts, hydrogen peroxide, methanol, and distilled water were used as an aqueousunaqueous bath. In addition, the coated samples were put to heat at 300, 450, 650, and 850℃ in an electric furnace for1 h. The crystalline phase of the coating was characterized by X-ray diffraction（XRD）. The chemical composition and microstructure of the coating were studied using energydispersive spectroscopy（EDS） and scanning electron microscopy analysis（SEM）. Moreover, the electrochemical measurement of Ti/（Ru ＋ Ti ＋ Ce）O2 coatings was carried out. Results show that with the increase in the number of coating layers, the quality of morphology is improved.Then, the best quality of coatings is obtained at six layers on the titanium substrate with electrolyte including TiO2/RuO2/CeO2 with the molar ratio of 70：5：25 after heat treatment at 450 ℃ for 1 h. Besides,with the increase in Ce02 content from 5 wt% to 25 wt% and the number of coating layers, higher thickness of about（20.0±0.1） μm and minimum over potential for chlorine evolution were obtained.