Peristaltic flow of a Sisko fluid in an endoscope: analytical and numerical solutions

This article deals with the peristaltic flow of a Sisko fluid in an endoscope. The inner tube of the endoscope is fixed, while outer tube is flexible. Continuity and momentum equations are utilized in the mathematical analysis and obtained both the analytical and numerical solutions. The analytical solution has been found by the homotopy analysis method and the numerical solutions are carried out by the shooting technique. The comparison of both the solutions are presented. And the quantitative behaviours of the solutions are discussed.     

侧颅底手术过程中脑及颅神经功能保护

手术是绝大部分侧颅底病变的首选治疗方式。因侧颅底解剖结构复杂,毗邻脑及重要血管神经,手术容易致死或致残,限制了该部位手术的实施。脑、后组颅神经、面神经、听力功能是该部位手术保护的重点,恰当处理功能保留和切除病变的关系、良好的外科操作技能以及合理使用介入、导航等新的辅助技术是侧颅底手术中实现器官功能保护的关键。     

Bubble behaviors in direct methanol fuel cell anode with parallel design

In this paper, the Volume of Fluid (VOF) method for tracking the gas-liquid interface is employed to investigate the carbon dioxide (CO₂) behaviors inside the anode of a direct methanol fuel cell (DMFC). The CO₂ bubble emergence processes from the catalyst layer (CL) to the gas diffusion layer (GDL) and then to the flow channels are studied with two different strategies. In the first strategy, the CL and GDL are modeled as a uniform porous layer; in the second strategy, they are modeled as a well-ordered-path GDL and a uniform CL. The simulation results show that the second modeling strategy can better capture and match the fundamental phenomena of CO₂ bubble formation and evolvement observed from the experiments inside a DMFC anode.     

Simulation of a Bubble Column by Computational Fluid Dynamics and Population Balance Equation Using the Cell Average Method

An axisymmetric computational fluid dynamics (CFD) simulation coupled with a population balance equation (PBE) has been applied in simulating the gas‐liquid flow in a bubble column with an in‐house code. The novel feature of this simulation is the application of the cell average method in a CFD‐PBE coupled model for the first time. The predicted results by this method are compared with those by the traditional fixed pivot method and experimental data. For both methods, the simulated results are in reasonable agreement with the reported experimentally measured values. However, the bubble size distributions determined by the cell average method are slightly better than those found by means of the fixed pivot method, i.e., the latter provides a smaller peak value and a wider bubble size distribution, and the probability density function of large bubbles is higher.     

炉料结构优化经济效益分析及建议

通过对生产数据的选择和处理、对品位与燃料比线性关系的定量分析,依据铁矿石品位综合评价法,确定了SiO2含量和品位的关系;在此基础上,进一步通过对炉料性价比的测算,提出了优化炉料结构的建议。建议指出了低品质的炉料结构优化路线不适合长期的集中选用,只能短期、间断性、少量地掺插使用;同时也给出了合理的炉料结构的优化措施。     

Escape trajectories are deflected when fish larvae intercept their own C-start wake

Fish larvae may intercept their own wake during sharp turns, which might affect their escape performance. We analysed C-starts of larval zebrafish (Danio rerio, Hamilton, 1822) using a computational fluid dynamics approach that simulates free swimming (swimming trajectory is determined by fluid forces) by coupling hydrodynamics and body dynamics. The simulations show that fish may intercept their own wake when they turn by 100–180°. During stage 1 of a C-start, the fish generates a strong jet at the tail that is shed into the wake. During stage 2, the fish intercepts this wake. Counterfactual simulations showed that wake interception increased the lateral force on the fish and reduced the fish''s turning angle by more than 5°. Wake interception caused no significant acceleration tangential to the trajectory of the fish and did not affect total power output. While experimental and simulation evidence suggests that fish larvae can either undershoot or intercept but not overshoot their wake, our simulations show that larger fish might be able to avoid intercepting their wake by either under- or overshooting. As intercepting its own wake modifies the fish''s escape trajectory, fish should account for this effect when planning their escape route.     

Numerical analysis of hydrocyclones with different vortex finder configurations

This paper presents a numerical study of the multiphase flow and performance of hydrocyclone by means of two-fluid model, with special reference to the effects of diameter, length and shape of vortex finder at a wide range of feed solids concentrations. The considered shapes include the conventional cylindrical style and the new conical and inverse conical styles. The simulation results are analysed with respect to cyclone flow and performance in term of cut size d₅₀, water split, Ecart probable E_p and inlet pressure drop. It is shown that when vortex finder diameter or shape varies, a compromised optimum performance can be identified, resulting in relatively small inlet pressure drop, E_p, and water split. Both d₅₀ and E_p are more sensitive to feed solids concentration than inlet pressure drop and water split. Overall, the effect of vortex finder length on the separation efficiency of particles is much less significant than diameter and shape, which shows opposite trends at low and high feed solids concentrations. All these results can be well explained using the predicted tangential and axial velocities and solid volume fraction.     

Terrific effect of H2 on 3D free convection MHD flow of C2H6O2H2O hybrid base fluid to dissolve Cu nanoparticles in a porous space considering the thermal radiation and nanoparticle shapes effects

In this article, the physical aspects of natural convection magnetohydrodynamic flow of Cu/Ethylene glycol-water nanofluid past a porosity vertical stretching sheet under impact of thermal radiation, shape and slip factor and suction/injection process has been analyzed using Runge- Kutta Fehlberg fifth order (RKF 5) numerical method. The influence of variable, different parameters such as nanoparticles shape factor, named hexahedron and Lamina on temperature and velocity profiles are exemplified quantitatively through graphs. Outputs demonstrate thermal radiation impact causes to produce heat and increase the temperature profile by increasing nanofluid molecules energy. Lamina shape nanoparticle has a greater effect on increasing Nusselt number (Nu) compared to hexahedron.