A Comprehensive Study on the Process of Greenhouse Gas Sequestration Based on a Microporous Media Model

Carbon dioxide geological sequestration is an effective method to reduce the content of greenhouse gases in the atmosphere of our planet.This process can also be used to improve the production of oil reservoirs by mixing carbon dioxide and crude oil.In the present study,a differential separation experiment(DL)based on actual crude oil components is used to simulate such a process.The results show that after mixing,the viscosity and density of reservoir fluid decrease and the volume coefficient increase,indicating that the pre buried gas induces fluid expansion and an improvement of the fluid rheological properties.These effects are interpreted using a pore scale model based on real scanning electron microscopy(SEM).The results show that increasing the pressure and reducing the viscosity are beneficial to increasing the micro oil displacement efficiency.Moreover,these effects can improve the production in the target area and slow down the decline of the formation pressure.Furthermore,in the case of fracture development in the reservoir(due to CO_(2)injection before exploitation),the risk of gas channelling,induced by the displacement pressure difference between injection and production wells,is avoided.

Digital image processing of saturation for two-phase flow in planar porous media model

In this paper, the accuracy of estimating stained non-wetting phase saturation using digital image processing is examined, and a novel post-processing approach for calculating threshold is presented. In order to remove the effect of the background noise of images and to enhance the high-frequency component of the original image, image smoothing and image sharpening methods are introduced. Depending on the correct threshold, the image binarization processing is particularly useful for estimating stained non-wetting phase saturation. Calculated saturation data are compared with the measured saturation data during the two-phase flow experiment in an artificial steel planar porous media model. The results show that the calculated saturation data agree with the measured ones. With the help of an artificial steel planar porous media model, digital image processing is an accurate and simple method for obtaining the stained non-wetting phase saturation.

Review of permeability evolution model for fractured porous media

The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.

Experimental and Numerical Investigations of the Hydrodynamic Characteristics, Twine Deformation, and Flow Field Around the Netting Structure Composed of Two Types of Twine Materials for Midwater Trawls

Nettings are complex flexible structures used in various fisheries.Understanding the hydrodynamic characteristics,de-formation,and the flow field around nettings is important to design successful fishing gear.This study investigated the hydrodynamic characteristics and deformation of five nettings made of polyethylene and nylon materials in different attack angles through numeri-cal simulation and physical model experiment.The numerical model was based on the one-way coupling between computational fluid dynamics(CFD)and large deflection nonlinear structural models.Navier-Stokes equations were solved using the finite volume ap-proach,the flow was described using the k-ωshear stress turbulent model,and the large deflection structural dynamic equation was derived using a finite element approach to understand the netting deformation and nodal displacement.The porous media model was chosen to model the nettings in the CFD solver.Numerical data were compared with the experimental results of the physical model to validate the numerical models.Results showed that the numerical data were compatible with the experimental data with an average relative error of 2.34%,3.40%,6.50%,and 5.80%in the normal drag coefficients,parallel drag coefficients,inclined drag coefficients,and inclined lift coefficients,respectively.The hydrodynamic forces of the polyethylene and nylon nettings decreased by approxi-mately 52.56%and 66.66%,respectively,with decreasing net solidity.The drag and lift coefficients of the nylon netting were appro-ximately 17.15%and 6.72%lower than those of the polyethylene netting.A spatial development of turbulent flow occurred around the netting because of the netting wake.However,the flow velocity reduction downstream from the netting in the wake region in-creased with increasing attack angle and net solidity.In addition,the deformation,stress,and strain on each netting increased with in-creasing solidity ratio.

Novel Optimization Approach to Mixing Process Intensification

An approach was presented to intensify the mixing process. Firstly, a novel concept, the dissipation of mass transfer ability(DMA) associated with convective mass transfer, was defined via an analogy to the heat-work conversion. Accordingly, the focus on mass transfer enhancement can be shifted to seek the extremum of the DMA of the system. To this end, an optimization principle was proposed. A mathematical model was then developed to formulate the optimization into a variational problem. Subsequently, the intensification of the mixing process for a gas mixture in a micro-tube was provided to demonstrate the proposed principle. In the demonstration example, an optimized velocity field was obtained in which the mixing ability was improved, i.e., the mixing process should be intensified by adjusting the velocity field in related equipment. Therefore, a specific procedure was provided to produce a mixer with geometric irregularities associated with an ideal velocity.

Effects of surfactants on graphene oxide nanoparticles transport in saturated porous media

Transport behaviors of graphene oxide nanoparticles（GONPs） in saturated porous media were examined as a function of the presence and concentration of anionic surfactant（SDBS）and non-ionic surfactant（Triton X-100） under different ionic strength（IS）. The results showed that the GONPs were retained obviously in the sand columns at both IS of 50 and200 mmol/L, and they were more mobile at lower IS. The presence and concentration of surfactants could enhance the GONP transport, particularly as observed at higher IS. It was interesting to see that the GONP transport was surfactant type dependent, and SDBS was more effective to facilitate GONP transport than Triton X-100 in our experimental conditions. The advection–dispersion–retention numerical modeling followed this trend and depicted the difference quantitatively. Derjaguin–Landau–Verwey–Overbeek（DLVO）interaction calculations also were performed to interpret these effects, indicating that secondary minimum deposition was critical in this study.

Determining the impact of rectangular grain aspect ratio on tortuosity–porosity correlations of two-dimensional stochastically generated porous media

Tortuosity is an important parameter for char- acterizing transport properties within porous materials and is of interest in a broad range of fields, such as energy storage and conversion materials. One of the parameters that impacts the tortuosity value is the geometry of the solid phase which, in this study, is considered as stochas- tically-placed rectangular particles. Through lattice Boltz- mann modelling （LBM）, we determined the impact of particle aspect ratio on the intrinsic tortuosity-porosity relationships of two-dimensional porous media composed of rectangular particles. These relationships were isolated for materials with grain （particle） aspect ratios of e { 1, 2, 3 } and porosities from [0.55 - 0.95]. We determined that a minimum of 6, 8 and 10 stochastic simulations, respec- tively, were required to calculate these average tortuosity values in laminar flow （Re 〈〈 1）. This novel application of the LBM to study the effects of porosity and aspect ratio of rectangular grains on tortuosity can be used in the tailoring of materials for clean energy.

Experimental and numerical research on squat silo and large size horizontal warehouse during quasi-steady-state storage

Traditional method to prevent stored grain from deterioration is to control grain temperature.A three dimensional(3-D)numerical model was established to study the temperature variation in outdoor squat silo and large size horizontal warehouse at quasi-steady-state.In this research,porous media model and solar radiation model were adopted.Numerical and experimental results showed that grain temperature was influenced by temperature of wall,height of grain and the distance between grain and the wall.Temperature changes dramatically at the top layer of grain heap due to solar radiation and heat convection at air layer.Temperature of grain close to wall increased with the increasing of ambient temperature.The model established in this research is suitable for predicting grain temperature in outdoor squat silo and large size horizontal warehouse.

Experimental and numerical study of a gas cyclone with a central filter

This paper studies a novel gas cyclone with a cylindrical fiter face installed in the center from the vortex finder to the bottom hopper.The experimental results show that this composite cyclone has a higher collection fficiency and a lower pressure drop than the original cyclone.The mechanisms for the improvement are analyzed by both physical experiments and numerical simulations.By measuring dust samples collected at different places it is revealed that the center filter can prevent fine particles from entering the inner vortex and escaping,which accounts for the increase of the collection eficiency.In addition,the flow field of the composite cyclone is simulated by computational fluid dynamics and compared with that of the original cyclone.The analysis shows that with the filter layer installed,the swirling flow disappears in the vortex finder,which decreases the kinetic energy dissipation and hence lowers the pressure drop.

Experiment and simulation research of storage for small grain steel silo

Knowing the temperature distribution in silo is a convenient and efficient way to control the process of grain storage.A three-dimensional(3-D)numerical model was used to study the temperature variation in small grain steel silo under quasi-steady state.In this study,experiments were conducted and porous media model was adopted.Results of numerical simulation and experiment were compared and the results indicated that grain temperature was influenced by temperature of the wall,grain stacking height,and the distance between grain and wall.The higher the wall temperature,the more the temperature increases.If the wall temperature is low,the effect of wall temperature on temperature distribution is significant.The temperature at the top part of grain varied obviously with the changes of temperature in air layer.Overall,numerical simulation results coincided with experimental results and the model established in this study is valuable for predicting grain temperature in steel silo.

3-D numerical simulation of curved open channel confluence flow with partially non-submerged rigid vegetation

For the study of the effects of partially non-submerged rigid vegetation on the free-surface confluence flow in a curved open channel,a numerical simulation is carried out by using the Volume of Fluid model combined with the porous media model with the software OpenFOAM.The model is first validated by using available experimental measurement data with a good agreement.Then,the characteristics of the separation zone generated by the centrifugal forces and the confluence flow are analyzed.Due to the resistance created by the vegetation,the velocities in the separation zone are more chaotic and the separation zone becomes smaller and more irregular.The reduction of the separation zone area of the vegetated flow in the convex bank is more significant than that in the concave bank.The velocities in the vegetated region become much smaller and remains so in the downstream flow after the vegetation region.Meanwhile,the vegetation compresses and divides the circulations in the flow area,rebuilding a structure with smaller circulations in the main flow and unclear circulations in the vegetation region.In addition,the bed wall shear stresses are significantly smaller in the vegetation region and the separation zone compared to the non-vegetated flow.This implies that the vegetation can have the effect of protecting the river bed from erosion.