An accurate calculation of the traffic density is a key factor in understanding the formation and evolution of the traffic-related emission concentration in urban areas. We have developed a twodimensional numerical mo...
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An accurate calculation of the traffic density is a key factor in understanding the formation and evolution of the traffic-related emission concentration in urban areas. We have developed a twodimensional numerical model to solve traffic flow/pollution coupled problem whose pollution source is generated by the density of vehicles. The numerical solution of this problem is calculated via an algorithm that combines the Characteristic method for temporal discretization with the Lagrange-Galerkin finite element method for spatial discretization. This algorithm is validated by varying certain physical parameters of the model (effective viscosity). We study the pollutant concentration diffusion impacted by the presence of an obstacle in a bifurcation topology traffic. We draw attention to the influence of the wind velocity as well as its direction on the pollutant concentration diffusion, in several situations. The temporal evolution of pollutant concentration at various relevant locations in the domain (before and after an obstacle) is studied for a single velocity and two winddirections. different regimes have been observed for transport pollution depending on time and the winddirection.
A simple analytical solution to two-dimensional (2d) ponding infiltration is essential for designing line-source or drip irrigation. We propose a new and simple approximate analytical method for calculating the 2ddis...
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A simple analytical solution to two-dimensional (2d) ponding infiltration is essential for designing line-source or drip irrigation. We propose a new and simple approximate analytical method for calculating the 2ddistribution of soil water with a 1-cm radius of ponding and uniform initial conditions and for estimating the horizontal and vertical distances of wetting fronts based on soil hydraulic parameters. The method assumes a semi-elliptical soil -wetting pattern and a one-dimensional profile of soil water at an arbitrary infiltration angle to solve the equation for the 2d movement of soil water and cumulative infiltration. We applied the numerical data simulated using HYdRUS-3d to validate the proposed method's parameters and evaluate the relationship between the wetting front and hydraulic parameters. The simulated results indicated that the assumptions were propitious to the fine -texture soils with air-entry suction larger than 10 cm. The ratio between the distances of the horizontal and vertical wetting fronts could be approximately predicted using the air-entry suction by analyzing the numerical results. The fitted results indicated that the parameters of the power function of the relationship between the distances of the horizontal and vertical wetting fronts and infiltration time could be described as polynomial and power functions of the diffusivity of saturated soil water. The approximate analytical solutions for the distance of the horizontal wetting front, depth of the vertical wetting front, and cumulative infiltration agreed well with other numerical simulations.
A 2d mathematical modeling was developed to analyze the mass transport in a proton exchange membrane fuel cell. The pin fins were inserted in the flow channel to improve reactant gas distribution in the gas diffusion ...
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A 2d mathematical modeling was developed to analyze the mass transport in a proton exchange membrane fuel cell. The pin fins were inserted in the flow channel to improve reactant gas distribution in the gas diffusion layer (GdL). The effect of rectangular and triangular shape of fins anddifferent title angles of 4, 6 and 8 degrees on the reactant gas transport were examined. The results showed that performance of rectangular fins are better than triangular fins due to increasing reactant spread over the GdL. The effect of three independent factors including length and width of blocks and hydrogen gas velocity on the response (hydrogen gas diffusion to GdL and pressure drop in anode channel) was investigated using analysis of variance (ANOVA). The results showed that block height and hydrogen gas velocity are the most important factors affecting the responses. Also, response surface methodology (RSM) method was used to predict the optimal conditions to achieve the minimum the pressure drop and maximum the total flux magnetic H-2 to GdL in anode channel. The result of the optimization process shows that a gas velocity of 4.22 m/s and the block with height and width of 3 mm are the optimal conditions. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
A comprehensive two-dimensional mathematical model was developed for the transport of carbon dioxide through hollow fiber membrane (HFM) contactors. The model was based on "non-wetted mode" in which the gas ...
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A comprehensive two-dimensional mathematical model was developed for the transport of carbon dioxide through hollow fiber membrane (HFM) contactors. The model was based on "non-wetted mode" in which the gas mixture filled the membrane pores for countercurrent gas-liquid contact. Laminar parabolic velocity profile was used for the gas flow in the tube side;whereas, the liquid flow in the shell side was characterized by Happel's free surface model. Axial and radial diffusion inside the fiber, through the membrane, and within the shell side of the contactor were considered in the model. Moreover, the model was validated with the experimental results obtained for carbon dioxide removal from CO2/CH4 gas mixture using polypropylene membrane contactor with distilled water as the liquid solvent. The modeling predictions were in good agreement with the experimental results for different values of gas and liquid flow rate, gas to liquid ratio, and temperature. (C) 2007 Elsevier B.V. All rights reserved.
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