Contaminant Flow and Transport Simulation in Cracked Porous Media Using Locally Conservative Schemes

The purpose of this paper is to analyze some features of contaminant flow passing through cracked porous medium,such as the influence of fracture network on the advection and diffusion of contaminant species,the impact of adsorption on the overall transport of contaminant wastes.In order to precisely describe the whole process,we firstly build the mathematical model to simulate this problem numerically.Taking into consideration of the characteristics of contaminant flow,we employ two partial differential equations to formulate the whole problem.One is flow equation;the other is reactive transport equation.The first equation is used to describe the total flow of contaminant wastes,which is based on Darcy law.The second one will characterize the adsorption,diffusion and convection behavior of contaminant species,which describes most features of contaminant flow we are interested in.After the construction of numerical model,we apply locally conservative and compatible algorithms to solve this mathematical model.Specifically,we apply Mixed Finite Element(MFE)method to the flow equation and Discontinuous Galerkin(DG)method for the transport equation.MFE has a good convergence rate and numerical accuracy for Darcy velocity.DG is more flexible and can be used to deal with irregular meshes,as well as little numerical diffusion.With these two numerical means,we investigate the sensitivity analysis of different features of contaminant flow in our model,such as diffusion,permeability and fracture density.In particular,we study Kd values which represent the distribution of contaminant wastes between the solid and liquid phases.We also make omparisons of two different schemes and discuss the advantages of both methods.

Numerical simulation and analysis of confined turbulent buoyant jet with variable source

In this work, experimental and numerical investigations are undertaken for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-ε turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The average devia- tion of the simulated temperature by realizable k-ε turbulent model and the measured temperature is within 2%. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear varia- tion that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits, particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during the whole course. Numerical experime- nts for constant, monotone increasing and monotone decreasing of inlet temperature are done to show its effect on the buoyancy force in terms of Richardson number.

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.