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The paper presents a numerical wave flume with porous media of variable porosity. A fully-Lagrangian computational method is developed for simulation of fluid flow interactions with porous media based on a projection-based (or Incompressible) SPH (Smoothed Particle Hydrodynamics) method. The continuity and Navier-Stokes equations are reformulated with incorporation of volume fraction, based on two-phase mixture theory. The proposed method benefits from a set of enhanced schemes and is therefore referred to as Enhanced Incompressible SPH (ISPH). The effect of porous media is represented by considering linear and nonlinear resistance force terms as well as incorporation of a newly-derived source term of PPE (Poisson Pressure Equation). The results are characterized by smooth and continuous pressure fields, as well as regular particle distributions at the fluid-porous media interface in absence of any artificial smoothing schemes. Since the local volume fraction of fluid phase particles is consistently calculated based on the volume fraction of surrounding porous phase particles, the method is capable of accurately reproducing fluid flow interactions with spatially varying porous media. Validations are made through a set of benchmark tests including fluid flow in a U-tube with uniform and multi-layered porous media, rapid seepage flows in rockfill dam, solitary wave attenuation over a porous bed, solitary wave interaction with a submerged porous structure and wave propagation over a submerged triangular permeable bar.

The paper investigates the energy conservation properties of two well-known projection-based particle methods, namely, MPS and ISPH methods. The enhancing effects of a set of refined schemes including Higher order Source term (HS), Higher order Laplacian (HL), Error Compensating Source (ECS), Dynamic Stabilizer (DS) and pressure Gradient Correction (GC) are shown through the simulations of a standing wave, oscillating drop and impacts of two fluid patches. The results highlight the superiority of corrected Taylor series consistent pressure gradient models for projection-based particle methods in providing accurate results with the best energy conservation as well as accurate reproductions of physical dissipations in fluid impact problems.

Pyrolysis gas chromatography/mass spectrometry and infrared spectrometry have been carried out for plasma-polymerized pyrrole (PPPy). The major thermal decomposition products have been identified as nitriles with less than four carbons and alkyl pyrroles. Evolution of only monosubstituted alkyl pyrroles, such as 2-methylpyrrole and 2-ethylpyrrole, suggests that PPPy consists of monosubstituted pyrrole rings. This is also supported by the result that the IR spectrum of PPPy differs from that of the electrochemically polymerized pyrrole, which consists of disubstituted pyrrole rings. Evolution of linear nitriles shows evidence that a PPPy molecule has the main chain containing nitrogen atoms. The mechanism of polymerization of pyrrole in the discharge is considered to be similar to that of aromatic hydrocarbons, which mechanism involves a process of production of acetylene. © 1993 John Wiley & Sons, Inc.

Zirconia (3mol% Y2O3) composite ceramics reinforced with 10, 20 and 40vol% α-alumina whiskers were prepared by hot-pressing at 1500°C under 30MPa for 30min, and the mechanical properties were measured. The α-alumina whiskers were fabricated by thermal decomposition of aluminum borate (9Al2O3⋅2B2O3) whiskers at 1500°C for 72h in air. Almost full dense composites (>99%) were obtained by 1500°C hot-pressing. Improvement of room temperature bending strength was observed because of the whiskers. In fracture tests at 1200°C, monolithic zirconia showed plastic deformation and bent, while the composite had a strength of around 300MPa. Elastic modulus and hardness increased linearly with increasing whisker content. As the whisker content increased, fracture toughness also increased due to crack deflection by whiskers and pull-out of whiskers, and showed a maximum value (around 5.4MPa⋅m1/2) at the whisker content of 40vol%, which was 1.4 times as large as that of monolithic zirconia.