CFD modeling of a headbox with injecting dilution water in a central step diffusion tube

For engineering applications of water dilution controlling system,the fluid dynamics of a mixed flow was studied with computational fluid dynamics(CFD) simulations and self-designed experimental set-up.In order to examine the predictability of CFD model for the headbox in industrial scale,two pulp suspensions before mixing were treated as homogeneous flows separately.Standard k-ε turbulence models with the mass diffusion in turbulent flows-species transport approach were applied in the simulations.A numerical simulation of this headbox model was analyzed with semi-implicit method for pressure linked equations scheme with pressure–velocity coupling.Results show that the model can predict hydrodynamic characteristics of headbox with injecting dilution water in a central diffusion tube,and the distribution of water content at the outlet of the slice lip is ideally normal at different speeds.

Static light scattering properties of a ZnO nanosphere aqueous suspension at visible and near-infrared wavelengths

The scattering properties of ZnO nanospheres with four different particle diameters of 10, 50, 100, and 200 nm suspended in water are investigated theoretical and experimentally in the spectral range of the entire visible range and part of the near-infrared region. The scattering properties of ZnO nanospheres suspended in water are described by employing three main parameters： the angular distribution of the scattering intensity I, the scattering extinction coefficient ascat, and the scattering cross section ascat. The results indicate that （i） at a certain wavelength, the angular distribution of the scattering intensity appears as an obviously forward- propagating feature, and the forward-scattering intensity is dominant gradually when the particle diameter in- creases from 10 to 200 nm, and （ii） the scattering extinction coefficient and cross section can be determined by using the measured transmittance changes of a pure water sample and a given ZnO sample; they all are shown to be dependent on the particle size and incident wavelength. The experimental results of four different scattering samples agree well with the theoretical predictions within the given wavelength range.

RESEARCH ON THE MOTION CHARACTERISTICS OF FIBER SUSPENSIONS IN A WEDGE-SHAPED FLOW

The motion of cylindrical particles in a wedge-shaped flow was studied. The velocity distribution of wedge-shaped flow was simulated and then the Euler-Lagrange model was used to calculate the motion of cylindrical particles. The evolution of particle location, velocity and orientation with time was examined. The trajectories of the particles with different particle Stokes number, rate of flow and initial particle orientation were drawn. The results indicate that the Stokes number and initial orientation are important parameters which mainly affect the particle motion.

PARTICULATE SUSPENSION FLOW INDUCED BY SINUSOIDAL PERISTALTIC WAVES THROUGH ECCENTRIC CYLINDERS： THREAD ANNULAR

This paper describes a new model for obtaining analytical solutions of peristaltic flow through eccentric annuli. A mathematical model of peristaltic pumping of a fluid mixture （as blood model） in a circular eccentric cylinders is presented and it is motivated due to the fact that thread injection is a promising method for placing medical implants within the human body with minimum surgical trauma. For the eccentric annuli, the inner cylinder is rigid and moving with a constant velocity V, and the outer one is hollow flexible cylinder that has a sinusoidal wave traveling down its wall. The coupled differential equations for both the fluid and the particle phases have been solved by using two methods and the expressions for the velocity distribution of fluid and particle phase, flow rate, pressure drop, friction forces at the inner and outer cylinders have been derived. The results obtained are discussed in brief. The significance of the particle concentration and the eccentricity parameter as well as the nature of the basic flow has been well explained.

Modified porous silica antireflective coatings with laser damage resistance for Ti:sapphire

Porous SiO2 antireflective (AR) coatings are prepared from the colloidal silica solution modified with methyltriethoxysilane (MTES) based on the sol-gel route. The viscosity of modified silica suspensions changes but their stability keeps when MTES is introduced. The refractive indices of modified coatings vary little after bake treatment from 100 to 150℃. The modified silica coatings on Ti:sapphire crystal, owning good homogeneity, display prominent antireflective effect within the laser output waveband (750-850 nm) of Ti:sapphire lasers, with average transmission above 98.6%, and own laser induced damage thresholds (LIDTs) of more than 2.2 J/cm2 at 800 nm with the pulse duration of 300 ps.

BOUNDARY LAYER EFFECTS ON SOLID PARTICLE MOTION AND EROSIVE WEAR

Lagrangian motion equation of a solid particle suspended in 2-D turbulent boundary layer flows has been modified. The effects of boundary layer on particle motion were studied. The critical nondimensional incidence velocities and angles to the wall from the edge of a 2-D incompressible turbulent boundary layer were presented for various nondimensional particle sizes and initial velocities. The numerical results clearly show that the effects of boundary layer on particle motion and particle impact erosive wear are very great. The presence of boundary layer decreases particle impact velocity and impact erosive wear.

Comparison study of several underwater light scattering phase functions

Scattering phase function is assumed to be one of the most significant factors in the inherent optical properties （lOPs） of natural water. According to three criteria proposed for assessment, several commonly used empirical phase functions are compared with their related practical or theoretical scattering distributions in terms of fitting errors under the circumstances of typical seawater and single-component polydisperse systems. The optimal factors corresponding to the minimum fitting errors are also calculated. It is found that both the one-term Henyey-Greenstein （OTHG） and two-term Henyey-Greenstein （TTHG） phase functions agree well with the theoretical ones for small particles, while the Fouriner-Forand （FF） phase function can be used in the case of suspensions with large suspended particles. The fitting accuracy of OTHG is the worst, FF is better and TTHG is the best.

VELOCITY DISTRIBUTIONS OF SUSPENDED SEDIMENT-LADEN FLOWS IN OPEN CHANNELS

Analysis on velocity distributions of steady, uniform suspended sediment-laden flow in open channels was presented. The sediment particle-particle interactions and the buoyancy effects due to density stratification were taken into account through a water sediment mixture's constitute relationship and an adapted Monin-Obukhov length scale to validate the theory for a wider spectrum of sediment concentrations. The developed model with the same Von Karman coefficient as that of a single phase flow was shown to be in the excellent agreement with the measurement results in the controlled experiments with both the low and heavy sediment concentrations.