Constant Injection Velocity Research Articles

Numerical simulation of foam flooding in porous media in the absence and presence of oleic phase

This paper presents a novel integrated approach for numerical simulation of foam core-flood experiments in the absence and presence of oil. The experiments consisted of the co-injection of gas and Alpha-Olefin Sulfonate (AOS) surfactant solution into Bentheimer sandstone samples initially saturated with the surfactant solution [see Simjoo & Zitha (2013)]. The foam model implemented is based on a local equilibrium and describes dependency of foam mobility reduction factor using several independent functions, such as liquid saturation, foam velocity, oil saturation and capillary number.First, a series of numerical simulation was conducted to investigate the effect of surfactant concentration on pressure drop across the core for the foam flooding in the absence of oil. To this end, the dry-out and gas velocity functions in the foam model were determined from the experimental data obtained at low and high-quality regimes of foam flow at a constant injection velocity. Next, pressure drop profiles of foam flooding at two different surfactant concentrations were modelled to determine the parameters of the surfactant-dependent function in the foam model. The simulation results fit the experimental data of pressure drops very well. Then, the numerical simulations investigated the oil displacement, by foam where the main goal was to determine the foam model parameters dedicated to the oil saturation-dependent function. The pressure drop across the core, oil-cut, and oil recovery factor were modelled, and an excellent match was obtained between the pressure profile and the oil recovery obtained numerically compared with those obtained from the corresponding core-flood experiments.

Entropy Analysis of a Coupled‐Convection Flow through a Vertical Channel Partially Filled by a Porous Medium with Injection/Suction and Slip Boundary Conditions

AbstractFlow fields, thermal fields, and entropy generation have been investigated for fully developed mixed convection flow between two vertical porous plates. The vertical channel is partially filled by a porous medium, and channel walls are subjected to a constant injection velocity at the left wall and constant suction velocity at the right wall. The viscous dissipation effects and velocity slip for the longitudinal component of the velocity at the channel walls are also taken into account. The momentum and energy equations for the mixed convection problem in the vertical channel are solved by means of the perturbation series method, by taking perturbation parameter proportional to the Brinkman number. For the present problem, numerical solution is also obtained and compared with the analytical solution. The effects of various pertinent parameters on the velocity distribution, temperature distribution, entropy generation rate, and Bejan number are investigated and discussed graphically.

Sensitivity analysis on resin transfer molding processes with edge effect and curing reaction characteristics

The mold filling time and resin flow front shape are of fundamental importance during resin transfer molding (RTM) processes, because the former influences productivity and the latter affects composites quality. In this article, considering both edge effect and curing reaction characteristics of the resin flow process, the sensitivity analysis method is introduced to investigate the sensitive degree of mold filling time and resin flow front shape to the key material and processing parameters. The function employed to describe the resin flow front shape is defined, and the mathematical relationships of the key physical parameters, such as fluid pressure sensitivity, flow velocity sensitivity, mold filling time sensitivity, and resin flow front shape sensitivity, are established simultaneously. In addition, then the resin infiltration process is simulated by means of a semi-implicit iterative calculation method and the finite volume method. The simulated results are in agreement with the analytical ones. The results show that under constant injection velocity conditions, both the change in the resin temperature and the alteration of the inlet velocity hardly affect the resin flow front shape, whereas the influence of edge permeability on the resin flow front shape is the greatest. This study is helpful for designing and optimizing RTM processes. POLYM. COMPOS., 36:2008–2016, 2015. © 2014 Society of Plastics Engineer

Miscible Displacements in Porous Media with Time-Dependent Injection Velocities

Miscible displacements in homogeneous porous media involving time-dependent injection velocities \(U(t)\) are analyzed. The displacements consist of periodic cycles that involve alternating stages of injection and production or of injection and soaking. Results of a linear stability analysis revealed that the growth rate of disturbances follows the overall trends of the velocity \(U(t)\) but with noticeable differences in periods of transition from production to injection. Furthermore, the growth rate of the time-dependent velocity was found to be smaller than that of a constant injection with a velocity equal to that corresponding to the minimum of \(U(t)\) while an overshoot was observed with respect to a displacement with a constant injection velocity equal to the maximum of \(U(t)\). Nonlinear simulations revealed that the dynamics of the flow can be drastically changed from those of the corresponding constant injection velocity and the changes depend on the period of the cycles, the amplitude of the velocity and on whether the displacement is initiated through an injection or a soaking stage. The enhancement or attenuation of the instability in comparison with the constant injection velocity increases with the cycles’ period and the amplitude of the velocity in the injection stage, with the effects of the former being more prominent. It was also found that, beyond a certain critical cycle period, it is possible to observe instability and fingering in the case of time-dependent displacements that actually result in a net zero flow.

Cyclic time-dependent reactive flow displacements in porous media

Reactive miscible flow displacements in homogeneous porous media with time-dependent injection velocities are analyzed. The displacements consist of periodic cycles that involve alternating stages of injection and extraction. Nonlinear simulations are used and the dynamics of the flows are characterized qualitatively as well as quantitatively in terms of the amount of generated chemical product. The simulations revealed that, when compared with constant velocity flows with the same overall amount of injected fluid, time dependent displacements show drastically different flow structures and chemical productivity. These differences are strongly dependent on the period of the velocity cycles and the scenario of whether the displacement is initiated through an injection or an extraction process. In particular, for non-monotonic viscosity profiles, displacements with larger period result in stronger chemical production while the effects of the velocity scenarios depend on the nature of the instability at the initial front. Moreover, for monotonically decreasing viscosity profiles known to be stable under constant injection velocity, only displacements starting with extraction can trigger instabilities and increase the amount of chemical product. Finally for monotonically increasing viscosity profiles, displacements that start with injection tend to generate more chemical product than the constant velocity flow and its counterpart starting with an extraction instead.

Numerical simulation of flow of micropolar fluids in a channel with a porous wall

AbstractTwo‐dimensional steady, laminar, and incompressible flow of a micropolar fluid in a channel with no‐slip at one wall and constant uniform injection through the other wall is considered for different values of the Reynolds number R. The main flow stream is superimposed by constant injection velocity at the porous wall. The micropolar model introduced by Eringen is used to describe the working fluid. An extension of Berman's similarity transformations is used to reduce governing equations to a set of nonlinear coupled ordinary differential equations (ODEs) in dimensionless form. An algorithm based on finite difference method is employed to solve these ODEs and Richardson's extrapolation is used to obtain higher order accuracy. It has been found that the magnitude of shear stress increases strictly at the impermeable wall whereas it decreases steadily at the permeable wall, by increasing the injection velocity. The maximum value of streamwise velocity and that of the microrotation both increase with increasing the magnitude of R. Copyright © 2010 John Wiley & Sons, Ltd.

A combined 1D3D–CFD approach for reducing mesh dependency in Diesel spray calculations

A 1D3D–CFD coupled spray model is proposed in this work for the simulation of Diesel sprays under non-evaporative conditions and constant injection velocity in time. The basic idea of the model is to reduce the poor estimations of the gas velocity and droplets/gas relative velocity obtained with the standard 3D–CFD Eulerian–Lagrangian spray model, when coarse meshes are used. The coupling has been achieved in the calculation of the momentum source interaction term. General considerations, descriptions and implementation of the model in a commercial CFD code are outlined. Diesel spray simulations performed using the proposed approach have been compared with those obtained with the standard 3D–CFD, 1D models and experimental data. Encouraging results were found in terms of spray evolution when changing meshes and ambient conditions.

Numerical simulation of flow of a micropolar fluid between a porous disk and a non-porous disk

Two dimensional steady, laminar and incompressible motion of a micropolar fluid between an impermeable disk and a permeable disk is considered to investigate the influence of the Reynolds number and the micropolar structure on the flow characteristics. The main flow stream is superimposed by constant injection velocity at the porous disk. An extension of Von Karman’s similarity transformations is applied to reduce governing partial differential equations (PDEs) to a set of non-linear coupled ordinary differential equations (ODEs) in dimensionless form. An algorithm based on finite difference method is employed to solve these ODEs and Richardson’s extrapolation is used to obtain higher order accuracy. The numerical results reflect the expected physical behavior of the flow phenomenon under consideration. The study indicates that the magnitude of shear stress increases strictly and indefinitely at the impermeable disk while it decreases steadily at the permeable disk, by increasing the injection velocity. Moreover, the micropolar fluids reduce the skin friction as compared to the Newtonian fluids. The magnitude of microrotation increases with increasing the magnitude of R and the micropolar parameters. The present results are in excellent comparison with the available literature results.

A computational model of wall shear and residence time of particles conveyed by steady flow in a curved tube

A finite-volume model of steady flow of an incompressible viscous fluid has been carried out in a smooth rigid 90° bend of circular cross-section. The inlet boundary conditions for laminar flow are either an entry Poiseuille regime or a constant injection velocity for a range of Dean number 140 ≤ De ≤430. A numerical test of turbulent flow was performed for De ∼22100 with a flat velocity profile at the model entry. The lower the role played by the viscous forces, the larger the distance necessary to set an outer shift of the peak axial velocity. The axial velocity of laminar flow depends not only on the value of the Dean number, but also on separate effects of the Reynolds number and of the tube curvature. The larger the laminar boundary layer at the bend inlet, the nearer from the entry the bend segment where the strongest secondary motion is located. With increasing Reynolds number, the secondary flow develops over a longer bend region and the wall shear rises. Upstream and downstream effect of the bend on the shear stress, as well as flow disturbances induced by very small curvature, were observed. The residence time of conveyed particles is enhanced by the presence of a curved section in the conduit with respect to a straight pipe only at the inner edge of the straight section located downstream from the bend. When the Reynolds number rises, the flow regime remaining laminar, the residence time is smaller in the whole pipe. However for turbulent flow, the residence time, which has much smaller values, takes its highest values in the exit straight section.

Couette flow of a stratified fluid with suction varying along a boundary

A viscous incompressible fluid between two plane boundaries is stratified by maintaining the planes at different temperatures. The upper plane moves with a uniform velocity. The suction/injection mechanism with constant injection velocity at the upper plane and suction velocity varying sinusoidally along the lower plane with a wave numberk is introduced at the boundaries. The steady linearised equations are solved using similarity variables for the velocity components. The wave numberk is shown to be effective in controlling the boundary layer thickness.

球状酸化トリウムの製造, (IV)

Further experiments on the preparation of thorium oxide microspheres using mixtures of ethyl- and isobuthyl-alcohol instead of iso-propyl alcohol were carried out to verify the previously proposed mechanism of microsphere formation.The mixed alcohol-water-ammonium nitrate system has a markedly different type of equilibrium diagram from that of isopropyl alcohol-water-ammonium nitrate system, and the shape of the equilibrium curve possessing minimum points vary with the composition of the mixed alcohol.Most of the results obtained on microsphere preparation with various ammonium nitrate concentrations in thorium hydrooxide sols at various mixed alcohol compositions showed fair agreement with the microsphere formation region estimated from the equilibrium diagram. The amorphous gel formation in the expected microsphere formation region may be explained from the “oil in water” type of emulsion formed by the mixing of the two liquid phases.The average particle diameter of the thorium oxide microspheres may be controlled within a range of 420μ at constant injection velocity by changing the mixed alcohol composition of the mixed alcohol, or the ammonium nitrate concentration in the sol.

A Constant-Area, Constant-Temperature Combustor

The theoretical performance of a piloted constant-area, constant-temperature combustor with mass addition is studied. Perpendicular injection of mass at constant injection velocity and temperature is assumed. Mixing between the injected mass and the main stream is regarded as instantaneous, and the flow is regarded as one-dimensional. The effect of chemical kinetics is considered by the use of a simple rate equation. The exit velocity corresponding to maximum throughput is found to be The combustor length required to accelerate the gases to this velocity is found to depend on the reaction rate constants, flame temperature, input flow variables, and the temperature of combustion. I t is determined that there exists a lower limit on the temperature below which the combustor is unstable.