A two-way coupling three-dimensional Vortex-In-Cell (VIC) method is developed for the simulation of gas-solid turbulent flow. The evolution of vortex elements and the motion of solid particles are tracked in the Lagra...
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A two-way coupling three-dimensional Vortex-In-Cell (VIC) method is developed for the simulation of gas-solid turbulent flow. The evolution of vortex elements and the motion of solid particles are tracked in the Lagrangian frame, while the flow field is solved by the vorticity Poisson equation on the Eulerian grid. Two-way coupling is implemented by introducing a vorticity source term induced by the motion of particle. This method is applied to simulate the particulate jet generated by solid particles falling from a circular orifice into unbounded quiescent air. The simulation results agree well with the experiment conducted by Ogata, which confirmed the validation of this method. The simulation results demonstrate that the air velocity radial distribution due to the particulate jet satisfies Gaussian distribution. The particle flow rate has little influence on the spread of particles, while velocity of particles increases with increasing the particle flow rate.
Recently, MAAP and MELCOR research teams completed a set of accident simulations to reconstruct the Fukushima-Daiichi accident in order to better understand severe accident progression. One result from this work was t...
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In this study, the relevant thermal-hydraulic, mechanic-material and burnup effect calculation models were established. On the basis of these mathematic and physic models, a thermal- mechanic-material coupling analysi...
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ISBN:
(纸本)9781510811843
In this study, the relevant thermal-hydraulic, mechanic-material and burnup effect calculation models were established. On the basis of these mathematic and physic models, a thermal- mechanic-material coupling analysis code for a dispersion-plate-type fuel assembly was independently developed with the consideration of the burnup effects. The coupling program was applied to perform the thermal-mechanical-material behavior analysis of a dispersion-plate-type fuel assembly. Major physical parameters at different burnup stages were well predicted, including flux distribution, temperature profile, Mises stress and mechanic deformations. The result shows that geometric sizes of flow channels are the key parameters determining the coolant flux distribution and the temperature profile of the edge plate presents substantial asymmetry as a result of asymmetric heat transfer caused by the asymmetric geometry. Furthermore, the equivalent stress of base material increased rapidly with burnup because of the thermal expansion and burnup effects, which resulted in substantial plastic deformation and mechanical damage. In addition, the mechanism and process of blistering was investigated for blistering prediction. The result shows that due to the increasing fission gas pressure and the deteriorating yield stress of the cladding, fuel plate blistering may happen when the burnup depth up to a certain value and fuel plate will finally fall into failure as a result of over plastic deformation.
ECC safety injection nozzles are usually placed at the primary circulation pipelines as for the Gen II-plus nuclear reactor. Small Break Loss of Coolant Accident (SBLOCA) may lead to Pressurized Thermal Shock (PTS) on...
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ISBN:
(纸本)9781510811843
ECC safety injection nozzles are usually placed at the primary circulation pipelines as for the Gen II-plus nuclear reactor. Small Break Loss of Coolant Accident (SBLOCA) may lead to Pressurized Thermal Shock (PTS) on the Reactor Pressure Vessel (RPV) wall. Based on the Emergency Core Cooling (ECC) of a 2nd generation plus PWR, the CFD software CFX was adopted to simulate the thermal mixing phenomenon of the sub-cooled water from safety injection nozzle and high temperature water or steam from the cold leg which later forms into stratified flow. Also the steam-water simulation takes the steam condensation into consideration and steam condensation is characterized by a relatively large interfacial area between the two phases. For simulations of single-phase thermal mixing, the temperature profiles of different points were obtained and agreed well with the experiment. For steam mixing with water, the gas volume profile and the condensation rate of the steam were obtained and compared with the experiment, and the effect of different injection nozzle water velocities were also studied.
A series of experiments were carried out in a batch reactor at the temperature range of 313-343 K to study the synthesis of tert -amyl ethyl ether from ethanol (EtOH) and 2-methyl-1-butene (2M1B) catalyzed by t...
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A series of experiments were carried out in a batch reactor at the temperature range of 313-343 K to study the synthesis of tert -amyl ethyl ether from ethanol (EtOH) and 2-methyl-1-butene (2M1B) catalyzed by the NKC-9 ion-exchange resin. The suitable reaction pressure was obtained by using the method of the Gibbs free energy minimization. The activity coefficients of each component were accurately calculated using the Wilson method, then, the equilibrium constants was obtained. The effect of catalyst size, stirring rate, temperature and EtOH/2M1B molar ratio was investigated at the chosen pressure, respectively. A kinetic model which considered the variation of each component volume was established. The method of nonlinear least square combined with genetic algorithm (NLS-GA) was proposed to estimate the kinetic constant in the forward direction. Results indicated that simulated kinetics results were agreed well with the experimental data.
Graphene is a one-atom-thick sheet of graphite comprising sp2-hybridized carbon atoms arranged in the hexagonal honeycomb *** removing the honeycomb lattices and forming nanopores with specific geometry and size,nanop...
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Graphene is a one-atom-thick sheet of graphite comprising sp2-hybridized carbon atoms arranged in the hexagonal honeycomb *** removing the honeycomb lattices and forming nanopores with specific geometry and size,nanoporous graphene has been demonstrated as a very high-efScient separation membrane,due to the ultrafast molecular permeation rate for its one atomic *** this presentation,we review the recent advances in nanoporous graphene membrane for the application of gas separation,including the recent theoretical and experimental works,the gas molecular transport mechanisms through the graphene nanopores and the advanced fabrication methods of this stateof-the-art ***,we give a brief introduction on our relevant *** proposed two mechanisms(direct mechanism *** mechanism) for the gas molecular permeation through nanoporous graphene *** quantified the relative contribution of the two mechanisms and showed that the direct flux can be described reasonably accurately using kinetic theory with an appropriate modification assuming steric molecule-pore *** identified an inhibition effect of non-permeable components on the permeation of permeable component,caused by the relatively weakening adsorption on the graphene surface and the blocking effect of non-permeable *** also reported an asymptotically pressure-dependent gas permeation flux owing to the isothermal adsorption *** addition,we demonstrated the potential of nanoporous graphene membranes in natural gas processing to efficiently separate CO2,H2 S,N2,H2 O and others from CH4 with high permeability and selectivity.
＜正＞Moving Particle Semi-implicit（MPS）method and Smoothed Particle Hydrodynamics（SPH）have been widely applied in modelling free surface ***,application of the meshfree methods was still limited due to the proble...
＜正＞Moving Particle Semi-implicit（MPS）method and Smoothed Particle Hydrodynamics（SPH）have been widely applied in modelling free surface ***,application of the meshfree methods was still limited due to the problem of compressible stress instability,which occurs in the presence of attractive forces when particles are approaching and the low accuracy of the numerical schemes for gradient operator.
Human carotid artery is bifurcated into two arteries in the neck,supplying blood to the brain and facial *** plaque tends to occur and develop in carotid artery sinus,where stenoses and other lesions can cause cerebra...
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Human carotid artery is bifurcated into two arteries in the neck,supplying blood to the brain and facial *** plaque tends to occur and develop in carotid artery sinus,where stenoses and other lesions can cause cerebral *** is accepted that the chronic exposure of the endothelial cells to lower wall shear stress(WSS)is associated with thickening of the vessel wall and development of atherosclerotic ***,platelet in blood is also accepted to play es-
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