Comparative study of different hydro-dynamic flow in microbial fuel cell stacks

This work has investigated the scaleup potential of microbial fuel cells(MFCs)under stacking mode.Stacking was done in batch mode and continuous mode.Batch feeding mode stacks were operated in electrical series(S)and parallel(P)mode.Continuous feeding mode stacks were kept in electrically parallel mode with different hydrodynamic patterns.The two continuous stacks were connected hydrodynamically in series(i.e.Parallel Dependent;PD)and parallel(i.e.Parallel Independent;PID)configurations.The performance of the continuous stacks was evaluated on the basis of COD consumption rate,power generation and coulombic efficiency.PID obtained highest power(0.47 mW)which was approximately 3.6 times that of PD configuration(0.13 mW).The rate of COD consumption was also highest in PID stack(3091.75 mg·L^(-1)·d ^(-1)).Coulombic efficiency of the PID stack was 14.26%which was approximately 292.8%of the PD stack.The results confirmed that the parallel electrical connection hybridized with the independent hydrodynamic flow gives the best possible results when working with stacking of MFCs.

Melting phenomenon in magneto hydro-dynamics steady flow and heat transfer over a moving surface in the presence of thermal radiation

The Lie group method is applied to present an analysis of the magneto hydro-dynamics（MHD） steady laminar flow and the heat transfer from a warm laminar liquid flow to a melting moving surface in the presence of thermal radiation.By using the Lie group method,we have presented the transformation groups for the problem apart from the scaling group.The application of this method reduces the partial differential equations（PDEs） with their boundary conditions governing the flow and heat transfer to a system of nonlinear ordinary differential equations（ODEs） with appropriate boundary conditions.The resulting nonlinear system of ODEs is solved numerically using the implicit finite difference method（FDM）.The local skin-friction coefficients and the local Nusselt numbers for different physical parameters are presented in a table.

STATIONARY DISCONTINUITY AND FLUTTER INSTABILITY OF WAVE PROPAGATION IN ELASTO-PLASTIC SATURATED POROUS MEDIA

In the present work a model based on the Biot theory for simulating coupled hydrodynamic behavior mi saturated porous media is utilized with integration of the inertial coupling effect between the solid-fluid phases of the media into the model. The non-associated Drucker-Prager criterion to describe nonlinear constitutive behavior of pressure dependent elasto-plasticity for the media is particularly considered. With no consideration of compressibility of solid grains and the pore fluid, the discontinuity and instability of the wave propagation in saturated porous media axe analyzed for the plane strain problems in detail. The critical conditions of stationary discontinuity and flutter instability in the wave propagation are given. The results and conclusions obtained by the present work will provide some bases or clues for overcoming the difficulties in numerical modeling of wave propagation in the media subjected to dynamic loading.

INSTABILITY AND DISPERSIVITY OF WAVE PROPAGATION ININELASTIC SATURATED/UNSATURATED POROUS MEDIA

A model based on the Biot theory for simulating coupled hydro-dynamic behavior in saturated-unsaturated porous media was utilized with integration of the inertial coupling effect between the solid-fluid phases of the media into the model. Stationary instability and dispersivity of wave propagation in the media in one-dimensional problem were analyzed. The effects of the following factors on stationary, instability and dispersivity were discussed. They are the viscous and inertial couplings between the solid and the fluid phases, compressibility of the mixture composed of solid grains and pore fluid, the degree of saturation, visco-plastic (rate dependent inelastic) constitutive behavior of the solid skeleton under high strain rate. results and conclusion obtained by the present work will provide some bases or clues for overcoming the difficulties in numerical modelling of wave propagation in the media subjected to strong and shock loading.

Influence of Copper Vapor on Low-Voltage Circuit Breaker Arcs During Stationary and Moving States

The influence of copper vapor on the low-voltage circuit breaker arcs is studied. A three-dimensional （3-D） magnetohydrodynamics（MHD） model of arc motion under the effect of external magnetic field is built up. By adopting the commercial computational fluid dynamics （CFD） package FLUENT based on control-volume method, the above MHD model is solved. For the mediums of air-1% Cu and air-10% Cu, the distributions of stationary temperature, pressure, electrical potential and the arc motion processes are compared with those of a pure air arc. The copper vapor diffusion process in the arc chamber and the distribution of copper vapor mass concentration are also simulated. The results shows that the copper vapor has a cooling effect on the arc plasma and can decrease the stationary voltage as well. Moreover, the presence of copper vapor can decelerate the arc motion in the quenching chambers. The maximal copper vapor concentration locates behind the arc root because of the existence of a ＂double vortex＂ near the electrodes.

EXPERIMENTAL RESEARCH ON CHARACTERISTICS OF HYDRODYNAMIC PRESSURE SPREADING IN THE BASE GAP OF ARCH INVERTED PLUNGE POOL

A detailed experimental research on characteristics of the hydrodynamicpressure spreading in the base gap of the arch inverted plunge pool was carried out. The features ofthe distributon of its ampitudes and spectral density and its characteristics in time domain fortwo conditions, i. e. , (1) a through gap and (2) a blind gap were given. The influence of the dampat the joint opening upon the hydrodynamic pressure inside the gap was also investigated.Accordingly, the stabilization mechanism of the arch invert plunge pool was worked out.

STUDY OF HYDRODYNAMIC FORCES OF SHIPS IN NARROW WATERWAY

The collision of ships in narrow waterway may occur for a variety of reasons.The hydrodynamic forces between two ships change the maneuvering characteristics of ships greatly.So based on the boundary element method, this paper proposes a calculation method for hydrodynamicinteraction forces between ships under meeting and passing conditions in narrow waterway. Theresults from this method are compared with the existing results obtained from other theoreticalapproaches, and they are in good agreement.