Immiscible displacement in capillary tubes is of great importance in many fields of study, particularly petroleum and civil engineering. In this study, a numerical model based on the “Control ...Volume-Finite Volume (CV-FV)” scheme is developed to characterize the dominant mechanisms controlling the two-phase displacement in a pore-doublet model. The effect of various parameters, namely the presence of wetting film on the walls, capillary number, fluids wetting characteristics, fluid-fluid interfacial tension and injection velocity, were investigated. A “Volume of Fluid-Continuum Surface Force” method was used to track the multi-phase volume fraction and the incorporation of the interfacial forces and fluid-wall contact line into the EOM (Equation of Motion). The numerical modeling results demonstrated the positive effect of wetting film on displacement, which contributed to a more efficient imbibition process. Additionally, the deterioration of the wetting characteristics of the ducts with respect to injection phase (via increasing the contact angle) was shown to have a negative impact on displacement efficiency due to the mobilization of the wetting film and blockage of the pore ducts. Increasing the injection velocity, by contrast, had a positive impact on displacement. The findings also highlighted that at very low IFT values, the flow becomes viscous dominant, thereby the wetting phase tends to flow faster through the larger tube.
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•Drainage and imbibition displacement in the pore-doublet model is studied.•Numerical simulations are validated against published experimental data.•Effects of injection velocity, wettability and interfacial tension (IFT) are discussed.•Presence of initial wetting-film increased the imbibition displacement efficiency.•For capillary dominated flow and contact angle above, the capillary blockage Phenomenon was observed.
During the recent earthquake, a lot of damage was reported from the historical monuments in the adjacent twin tunnels. While scientific research shows, the vulnerability of other monuments is much ...less than the monuments adjacent twin tunnels. The first type of
Hankel
function was used to study scattering waves in time domain analysis. The time domain results were transferred to the frequency domain using
Fourier
transform criteria. Extra stress concentrations were calculated based on the results of frequency domain analysis and developed a new approach to scattering.
Arg-Karim Khani
citadel and twin subway tunnels in Shiraz were selected as a case study. Three near-field earthquakes to perform the time history analysis were considered. The statistical difference based on Mann–Whitney test illustrates the seismic behavior of monument with and without considering twin tunnels, which shows that there is significant difference between them. The mean of
P
value amount of this comparison in horizontal and vertical direction is 0.005 and 0.016, respectively (
P
value < 0.05). The integrated analysis shows the importance of frequencies in creating different scattering around twin tunnels, which depends on the distance tunnels, the diameter of the tunnels, the soil characteristics, the seismic wave types, etc.
The fast population growth in the metropolitan areas of the province of Tehran has led to the scarcity of land and inevitable expansion of urban construction to non-engineered fills and ...construction/demolition waste disposal sites. An abandoned aggregate quarry, infilled with construction wastes over 16 years, has been recently selected for a new development project consisting of several multi-storey commercial and residential complexes (up to 7 storeys). This study was aimed at delineation of the waste materials, geophysical and field and laboratory geotechnical characterisations prior to foundation design, and the design of the excavation programme. Geo-electric resistivity test was used to delineate the waste materials from natural ground materials. Surface and downhole P- and S-wave velocity measurements were used for the estimation of dynamic elastic properties of the wastes. In total, 12 boreholes (15–30 m deep) along with 10 test pits (4–8.5 m deep) provided the opportunity for visual observations of the waste materials, necessary sampling for compositional analyses, laboratory shear strength tests and determination of waste deposit thickness in different regions of the site. Manual standard penetration test (SPT) was also used to evaluate in situ stiffness of the fine materials of the waste. Six field plate load tests were performed on the waste materials at their natural water content conditions and at saturated (flooded) ground conditions to determine their compressibility and the ground reaction modulus. Based on the results from extensive characterisation programme, it was concluded that the waste materials are in a metastable state and exhibit heterogeneity across the site. The findings of current case study can provide new insight into construction/demolition waste behaviour, using available geophysical and geotechnical tools and testing procedures for characterisation, and eventually helping in reliable design of foundations for new development projects.
Damage of the historical monuments was reported during the earthquakes in the nearby underground tunnels such as twin tunnels. The dynamic stress concentration has been used as a major parameter that ...evaluates the damage of underground structures. In this study, the dynamic interaction between arge-Karim Khani citadel and twin tunnels was investigated subjected to seismic P waves. The scattered wave fields by twin tunnels were determined with wave function expansion and Fourier transform criteria. In this regard, a new approach was employed to determine scattering based on dynamic stress concentration criteria around two circular tunnels. The seismic responses of twin tunnels were calculated with a verified finite element method using different ranges of the incident seismic wave. The dimensionless analysis was used to evaluate DSCF as known criteria to evaluate scattering. In this way, the different ranges of variables including incident wave angles, frequencies, tunnel sizes, and distance between monitoring point and tunnel center were considered in dimensionless analysis. The results illustrate that DSCF was decreased with increasing the position off the monitoring point and reducing the size of tunnels.
Analyzing multiphase flow in capillaries can provide valuable insight into fluid flow modeling in different branches of engineering, particularly petroleum engineering, carbon dioxide sequestration, ...polymer processing, and drug delivery. Wall wettability is one of the most critical parameters significantly affecting fluid distribution within a capillary system. The tendency for wettability is usually described using the contact angle. In this research, the impact of dynamic contact angles was investigated, and the results were compared with published experimental data. For this purpose, a three-dimensional numerical scheme using computational fluid dynamics was developed to simulate two-phase immiscible flow through angular pores at micro-scale. In comparison with previously published numerical simulations assuming a static contact angle, a better agreement between the experimental data and numerical simulations was observed in this study. Results of this study demonstrated that using dynamic contact angle models can reduce the numerical error from 150% to 35%. Therefore, it can be concluded that the effects of dynamic contact angles on viscous dominant flows are not negligible. In addition, analyzing multiphase flow within different angular pores demonstrated the importance of dynamic contact angle implementation for angular pores with sharp corners. The accuracy and computational efficiency of the proposed numerical scheme were improved using a dynamic mesh adaptive refinement technique. This method improved the numerical simulations' accuracy while simultaneously reducing computational costs.
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•Immiscible drainage process in 3D angular capillaries was investigated numerically.•Rate-dependent dynamic contact angle models are taken into account mathematically.•The accuracy of this solution was validated using experimental and analytical data.•Dynamic mesh adaptive technique was significantly reduced the statistical error.•DCA models reduced the discrepancy between the numerical and the experimental data.
Earthquakes of large magnitudes cause fault ruptures propagation in soil layers and lead to interactions with subsurface and surface structures. The emergence of fault ruptures on or adjacent to the ...position of existing tunnels cause significant damage to the tunnels. The objective of this paper is to study the interaction of an embedded tunnel within a soil layer and the soil deformations imposed upon by normal faulting. A centrifuge modeling under 80-g acceleration was conducted to investigate the rupture propagation pattern for different relative tunnel positions. Compared with the free field condition, due to tunnel and normal fault rupture interactions, focused on soil relative density and tunnel rigidity in this research, found that they can dramatically modify the rupture path depending on the tunnel position relative to the fault tip. The tunnel diverts the rupture path to its sides. This study presents the normal fault-tunnel interaction with the tunnel axis parallel to the normal fault line, to examine the changes that take place in fault rupture plane locations, the vertical displacement of the ground surface with tunnel presence and the effect of tunnel rigidity and soil density on fault tunnel interaction.
Due to the importance of surface and subsurface settlements to prevent damages to building foundations and sensitive structures in the urban cities, in this study, the ABAQUS finite element software ...has used to conduct a series of numerical modeling analysis on ground surface settlement caused from the asynchronous excavation of twin-tunnel. The effects of tunnel diameter, center-to-center tunnel spacing, and tunnel depth are discussed in detail and the shape of the surface settlement curves is also plotted. The numerical modeling has been verified by the results of three sequential twin-tunneling centrifuge tests conducted by the City University of London with 94.22%, 98.71% and 99.56% accuracy, respectively. Based on the results of this study, reducing the tunnel diameter decreases the amount of the maximum ground surface settlements and reducing the depth of tunnels and the distance between twin-tunnel to less than 2D (D is the diameter of the tunnels) increase the maximum surface settlements. Installation of 30 cm of tunnel lining can decrease the maximum ground surface settlement up to almost 79%.
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•A numerical scheme using CFD methods was developed to investigate a fluidized bed dryer.•Numerical results were validated with our pilot plant experimental data.•Effects of gas ...injection temperature and velocity, gas distributor, and initial moisture were studied.•Some numerical simulations were conducted, and an optimized configuration was proposed.
Fluidized Bed Dryer (FBD) is one of the efficient methods for drying moist particulate products. At the same time, the design and optimization of a full industrial scale FDB requires extensive studies. Using a pilot-scale dryer can be deemed as an efficient tool to obtain essential information on the drying phenomenon. Although these kinds of experimental analyses can provide valuable insight, there are still some operational limitations, including high-pressure or high-temperature conditions, which make the use of a computational procedure highly desirable. In this study, Computational Fluid Dynamics (CFD) approach has been employed to investigate a dryer. The results of numerical simulations were verified using the experimental data obtained from a pilot-scale dryer. The present investigation aims to study the effects of different operating conditions. It was observed that the impacts of gas inlet temperature were negligible, as the dryer was equipped with a thermal jacket, while the gas injection velocity had significant effects on the dryer’s performance. Moreover, the efficiencies of the conical and horizontal gas distributors were compared and it was concluded that the conical configuration results in better performance. The numerical and experimental investigation from this study can facilitate the design and scale-up of an industrial dryer plant.
Fluid flow modeling in porous media requires solving relevant governing equations, which are inherently nonlinear. However, some simplifications are usually made to make them linear. One of those ...common assumptions is invariant rock properties with respect to reservoir pressure. However, there are some situations, including pressure-dependent porous media, where this assumption would not be applicable. Hence, the solution of the nonlinear diffusivity equation shall be sought for such cases. The main goal of this study is to present a new analytical solution to the diffusivity equation and a numerical scheme considering exponential decreases in the petrophysical properties with reservoir pressure. The diffusivity equation was solved using the assumed exponential functions, and analytical solutions are provided in this paper. Besides, Computational Fluid Dynamics methods were utilized to verify the accuracy of the derived equations. The developed analytical equations and numerical scheme were then applied over several pressure-dependent porous media cases, and our comparison study showed that neglecting the pressure-dependency of the petrophysical properties will lead to significant errors (approximately 40%). Based on the introduced solutions, we also proposed a new set of type-curves that can be used in well-testing analyses of the deformable porous media.
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•Pressure propagation in pressure-dependent porous media is investigated.•An Analytical solution is provided for pressure-dependent diffusivity equation.•A Numerical model is developed to investigate various compressibility coefficients.•Neglecting the pressure-dependency effect leads to significant error.•A set of type-curves is presented for well-test and aquifer analyses.
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