Applied Mechanics and Materials Vols. 423-426

Abstract: The dust collected in the polar plates can be washed out by a spraying system in the wet electrostatic precipitator. It is important to keep the spraying system having a high efficiency lest the dust returns to the gas again. The performance of the spraying system in the electrostatic precipitation and its influence on the dust collection efficiency are presented in the paper. The atomization characteristic of the spraying nozzle is measured by changing the water pressure and operating voltage. The results show that: Collection efficiency of the electrostatic precipitation is over 99.5 % when the water pressure is 0.4 MPa.When the spraying mists diameter is 100 μm, the collection efficiency is 92 % for the dust diameter under 10 μm. It will provide a basis for the design of spraying system in wet electrostatic precipitation by this analysis.

Abstract: A method for the analysis of the axially symmetric fluid-structure interaction (FSI) problems which has free surfaces, based on the particle finite element method (PFEM), is proposed. To solve the incompressible axially symmetric N-S equations, a stabilized formulation based on the finite calculus procedure is used in the fractional step method. The FSI problem is performed with a staggered scheme. And a flexible boundary is used between the fixed boundary and the moving boundary so as to replace the friction. The reliability of the present method is demonstrated by the comparisons of the results from the classical method and the present results for the recoil absorber simulation. The present method can improve the efficiency and veracity in the design of machines which have free surfaces.

Abstract: Laminar natural convection heat and momentum transfer in fluid-filled, square enclosures partially heated at one side and cooled either at the top or at the bottom, is studied numerically. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. Simulations are performed using the Rayleigh number based on the cavity width, the thermally-active fraction of the partially heated sidewall, and the Prandtl number of the working fluid, as independent variables. It is found that the top cooling is definitely more efficient than the bottom cooling. In both cooling configurations the average Nusselt number of the cavity increases as each controlling parameter is increased. On the basis of the results obtained, a set of dimensionless correlations is developed.

Abstract: Rayleigh-Taylor instability problem with large density ratios is simulated by RKDG method which is developed for Euler equations with an additional body force corresponding to the gravity. The interface capturing ability of RKDG method is testified, while the density ratio (heavy to light) ranges from 3 to 20. Numerical results show that RKDG method has capability to pursue contact discontinuity in Rayleigh-Taylor instability with large density ratio. In the late stage of Rayleigh-Taylor instability problem, the contact line begins to crash, but the numerical solution is still smooth near the interface and has high resolution.

Abstract: The existence of Neumann boundary is a major cause of the poor accuracy and instability of collocation-based methods. Taking a Poisson equation with Neumann boundary condition as the model, the present paper studies the effects of two different radial point interpolation shape functions and their parameters on the accuracy of numerical solutions of the equation. We also study the effects of methods including fictious point method, nodes densification method and Hermite collocation method on the improvement of numerical accuracy. By comparison of analytic and numerical solutions computed using a program developed during research, we obtain parameters of shape functions and methods of treatment of Neumann boundary conditions that can be adopted to give better numerical accuracy.

Abstract: A mathematical model was developed in describing flow behaviors of a microchannel between two parallel flat plates. The model was solved numerically using the commercial software, Fluent, and the effect of microchannel size and structure on the transition Reynolds number (R_ec) was analyzed. Comparison between model prediction and experimental data in literature shows a good agreement, which verifies the reliability of the model. The results also show that the equivalent diameter has little effect on R_ec. The magnitude of the R_ec depends largely upon the contraction ratio. Consequently, the R_ecs under different contraction ratios were determined, which provides a theoretical basis for performance analysis and optimization of microchannel.

Abstract: In order to summarize the kinematic law of in-run stage of free skiing aerials and identify the feasibility and scientificity of the method of laboratory emulation study, this study employed video analysis method etc. to compare the kinematic indices of laboratory in-run emulation and actual in-run stage on snow. Results show that the actions of our national ski steam are highly identical and there is no significant difference between laboratory and actual parameters. So we can safely come to the conclusion that laboratory emulation is feasible in the analysis of the in-run phase of free skiing aerials.

Abstract: Parachuting injuries among cadet pilots often occur because they undergo extensive training within a short period of time. To explore the injury mechanism and to prevent injuries, this paper investigated the injury risk factors for the military parachuting of cadet pilots. A prospective study of static line parachute descents by Chinese Air Force cadet pilots was performed. The study indicates that 153 cadet pilots were injured, with a total of 168 injuries. The injury rates associated with extrinsic and intrinsic risk factors were compared and analyzed by using orthogonal multivariate analysis. Landing is the most dangerous part of parachuting, causing 88% of injuries. Extrinsic factors associated with increased injury rates are higher surface wind speed and third-generation protective boots. Intrinsic factors associated with reduced injury rates are excellent mental qualities, excellent parachuting movements, and female cadet pilots. Strengthening parachuting movements and mental qualities, approving jumps only when basic parachuting conditions are met, and improving protective equipment are recommended strategies for preventing parachuting injuries.

Abstract: Upper limb fracture is easily found in the truck-to-pedestrian road traffic accident. And it is important to understand and elucidate the biomechanics of upper limb fractures caused by the frontal structure of the truck. Finite element (FE) analysis could potentially help in the understanding the biomechanical response mechanism of upper limb fracture. In this study, THUMS (Total Human Model for Safety) was applied to reconstruct the upper limb fracture in a real-world truck-to-pedestrian accident. Totally two FE simulations were conducted to find out the most likely scenario in this case. Analyzing the simulations of two possible scenarios clearly demonstrated that the simulation result of collision-to-left scenario was consistent with the autopsy finding, and bending mechanism could explain how the upper limb fracture occurs. Then we drew a conclusion that FE analysis is a valuable method for us to understand the biomechanical mechanism of upper limb fracture in the forensic practice.

Abstract: Nitric oxide (NO) is a critical intra-and extra-cellular signaling molecule that mediates a broad variety of physiologic and pathophysiologic events, and has prompted rapid growth of investigations in investigating its physiology and generation mechanism of corresponding diseases. In this paper, a picomol assay of NO screening method using fluorescent derivatization combined with high-throughout microplate format has been developed and successfully applied to the determination of NO in biological samples. The satisfied detection limit and recovery of the proposed method demonstrates that it can be competent for the sensitive determination of NO in extremely small volume of biological sample.