Sharif Digital Repository

Production or injection of fluids from/in an underground storage site causes variations of pore pressure and stress states. These fluctuations significantly affect implications for hydraulic fracturing, wellbore integrity, top surface subsidence and heave, fault-reactivation, and stability of reservoir and caprock. Therefore, in order to keep optimal conditions during the process of gas injection and production, it is of paramount importance to have accurate estimates of the pore pressure. In this investigation, coupled fluid flow and geomechanical simulations, as well as rock mechanical tests, are performed on the Sarajeh field, Iran to investigate the geomechanical behavior of the Sarajeh... 

One of the most popular models that has been applied to predict the fluid velocity inside the fracture with impermeable walls is the cubic law. It highlights that the mean flux along the fracture is proportional to the cubic of fracture aperture. However, for a fractured porous medium, the normal and tangential interface conditions between the fracture and porous matrix can change the velocity profile inside the fracture. In this paper, a correction factor is introduced for flow equation along the fracture by imposing the continuity of normal and tangential components of velocity at the interface between the fracture and porous matrix. As a result, the mean velocity inside the fracture... 

In this article, a computational model is presented for the analysis of coupled thermo-hydro-mechanical process with phase change (evaporation/condensation) in fractured porous media in order to model multiphase fluid flows, heat transfer, and discontinuous deformation by employing the extended finite element method. The ideal gas law and Dalton's law are employed to consider vapor and dry air as miscible gases. To take into account the phase change, latent heat and specific vapor enthalpy are incorporated into the physical model. The set of governing equations consists of linear momentum for the solid-phase, energy balance equation and mass conservation equations of water species (liquid... 

Capacitance-Resistive Model (CRM), as a fast yet efficient proxy model, suffers from some limitations in modeling relatively complex reservoirs. Some current improvements on this proxy made it a more powerful simulator with updating parameters over time. However, the model's intrinsic uncertainty arisen from simplifying fluid-flow modeling by some limited number of constant parameters is not addressed yet. In this study, this structural limitation of CRM has been addressed by introducing a time-correlated model error, including stochastic and non-stochastic parameters, embedded into this proxy's formulation. The error term's non-stochastic parameters have been tuned to be used in forecasting... 

Circulating tumor cells (CTCs) isolation from a blood sample plays an important role in cancer diagnosis and treatment. Microfluidics offers a great potential for cancer cell separation from the blood. Among the microfluidic-based methods for CTC separation, the inertial method as a passive method and magnetic method as an active method are two efficient well-established methods. Here, we investigated the combination of these two methods to separate CTCs from a blood sample in a single chip. Firstly, numerical simulations were performed to analyze the fluid flow within the proposed channel, and the particle trajectories within the inertial cell separation unit were investigated to... 

The separation of cancer cells from a heterogeneous biological sample such as blood plays a vital role in cancer study and future treatments. In this paper, we designed and investigated two microfluidic devices for cancer cell separation, including a serpentine inertial device and an integrated inertial-magnetophoretic device. Firstly, numerical modeling was carried out to study the fluid flow, particles’ trajectories in the inertial device. Then the device was fabricated using soft photolithography and suspension of two types of microparticles with the size of 10 and 15 µm were injected into the microchannel separately to investigate the particles’ trajectories and focusing behavior at... 

We have investigated the usage of a Dielectric Barrier Discharge (DBD) plasma actuator to improve the aerodynamic performance of an offshore 6 MW wind turbine. By controlling the aerodynamic load combined with pitch angles of 2, 5, and 10 degrees, we studied the plasma actuator effect on the overall harvested power. Actuators were installed in single and tandem configurations in different chord-wise locations to find the optimum design. The improved phenomenological model developed by authors was used in an analysis to simulate the interaction of the electrostatic field, the ionized particles and the fluid flow. A design software was used to estimate the harvested power of the real 3D blade.... 

During the low salinity waterflooding (LSWF) of a viscous asphaltic oil reservoir, fluid-fluid interactions have a large influence on the fluid flow, pore-scale events, and thus oil recovery efficiency and behavior. In-situ water-in-oil (W/O) emulsion formation is a consequence of crude oil and brine interfacial activities. Despite the published studies, the pore-scale mechanisms of W/O emulsion formation and the role of injected brine salinity, injection rate, and pore-scale heterogeneity on emulsion formation and stability requires a deeper understanding. To address these, a series of static and dynamic micro-scale experiments were performed. The salinity dependent oil-brine interactions... 

The bronchial tree plays a main role in the human respiratory system because the air distribution throughout the lungs and gas exchange with blood occur in the airways whose dimensions vary from several centimeters to micrometers. Organization of about 60,000 conducting airways and 33 million respiratory airways in a limited space results in a complex structure. Due to this inherent complexity and a high number of airways, using target-oriented dimensional reduction is inevitable. In addition, there is no general reduced-order model for various types of problems. This necessitates coming up with an appropriate model from a variety of different reduced-order models to solve the desired... 

This study provides a stability analysis of flexible rotating pipes taking into account the simultaneous effects of internal and external fluid loading. Using the Euler-Bernoulli beam assumptions, governing equations for flexural vibrations of rotating pipes are obtained. The internal flow characteristics and the double gyroscopic effect are taken into account when deriving the structural equations coupled with the internal flow. External fluid loading is determined by a special linearization of the Navier-Stokes equations. Considering the circular wall of the pipe as an impermeable boundary to the flow, fluid-induced forcing functions are obtained and then applied to the structural... 

Among numerous methods which have been employed to reinforce the thermal efficiency in many systems, one is the thermal radiation which is a mode of heat transfer. Another way to improve the thermal efficiency is the utilization of the porous media. The present work includes the study of micropolar flow with allowance for thermal radiation through a resistive porous medium between channel walls. The governing coupled partial differential equations representing the flow model are transmuted into ordinary ones by using the suitable dimensionless coordinates, and then, quasi-linearization is employed to solve the set of relevant coupled ODEs. Effects of physical parameters on the flow under... 

The Computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulation may be applied to predict the hydrodynamic behavior of dense particle–fluid flows. The main drawback of this simulation is the long computational time required owing to the large number of particles and the minute time-step required to maintain a stable solution. In this work, a new method to improve the efficiency and accuracy of CFD–DEM simulations is presented. The particle stiffness coefficient is used as a flexible parameter to improve the accuracy and efficiency of the model. The particle concentration distribution results are compared with experimental one’s to derive the optimum effective... 

The bronchial tree plays a main role in the human respiratory system because the air distribution throughout the lungs and gas exchange with blood occur in the airways whose dimensions vary from several centimeters to micrometers. Organization of about 60,000 conducting airways and 33 million respiratory airways in a limited space results in a complex structure. Due to this inherent complexity and a high number of airways, using target-oriented dimensional reduction is inevitable. In addition, there is no general reduced-order model for various types of problems. This necessitates coming up with an appropriate model from a variety of different reduced-order models to solve the desired... 

This study provides a stability analysis of flexible rotating pipes taking into account the simultaneous effects of internal and external fluid loading. Using the Euler-Bernoulli beam assumptions, governing equations for flexural vibrations of rotating pipes are obtained. The internal flow characteristics and the double gyroscopic effect are taken into account when deriving the structural equations coupled with the internal flow. External fluid loading is determined by a special linearization of the Navier-Stokes equations. Considering the circular wall of the pipe as an impermeable boundary to the flow, fluid-induced forcing functions are obtained and then applied to the structural... 

Among numerous methods which have been employed to reinforce the thermal efficiency in many systems, one is the thermal radiation which is a mode of heat transfer. Another way to improve the thermal efficiency is the utilization of the porous media. The present work includes the study of micropolar flow with allowance for thermal radiation through a resistive porous medium between channel walls. The governing coupled partial differential equations representing the flow model are transmuted into ordinary ones by using the suitable dimensionless coordinates, and then, quasi-linearization is employed to solve the set of relevant coupled ODEs. Effects of physical parameters on the flow under... 

The Computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulation may be applied to predict the hydrodynamic behavior of dense particle–fluid flows. The main drawback of this simulation is the long computational time required owing to the large number of particles and the minute time-step required to maintain a stable solution. In this work, a new method to improve the efficiency and accuracy of CFD–DEM simulations is presented. The particle stiffness coefficient is used as a flexible parameter to improve the accuracy and efficiency of the model. The particle concentration distribution results are compared with experimental one’s to derive the optimum effective... 

A new characteristic-based method is developed and used for solving the mixed and forced convection problems. The nano-fluid flow with heat transfer is simulated with a novel characteristic-based scheme in closed domains with different aspect ratios. For this purpose, a FORTRAN code has been written and developed. Water as a pure fluid and water-titanium dioxide as a nano-fluid were considered. The governing equations are solved by the finite volume utilizing a characteristic-based scheme for the convective fluxes. The simulation is done at Grashof numbers from 100 to 104, Reynolds numbers from 100 to 1000, and volume fractions of nano-particles from 0% to 10%. Streamlines, isotherms,... 

In this paper, the stability of pipes conveying fluid with viscoelastic fractional foundation is investigated. The pipe is fixed at the beginning while the pipe end is constrained with two lateral and rotational springs. The fluid flow effect is modeled as a lateral distributed force, containing the fluid inertia, Coriolis and centrifugal forces. The pipe is modeled using the Euler-Bernoulli beam theory and a fractional Kelvin-Voigt model is employed to describe the viscoelastic foundation. The equation of motion is derived using the extended Hamilton's principle. Presenting the derived equation in Laplace domain and applying the Galerkin method, a set of algebraic equations is extracted.... 

Static and dynamic properties of porous media are highly dependent on its internal geometry. CT scan images are generally used to characterize porous media geometry. Direct simulation of fluid flow on CT scan images is possible but considerably time-consuming. In this study, a new method was developed for extracting a simplified representation known as “pore network model” by utilizing a rigorous algebraic-analytical method. By using a moving frame in the 3D matrix of the CT scan image and stepwise identifying-removing of image components, running time for a 4003 voxels sample in a typical computer system decreased to less than 350 s. The identification of throats was based on a new... 

To increase the flight endurance of a Micro air vehicle (MAVs), which operates at low Reynolds number flow, one way is to harvest energy during its flight. By inspiring from the nature when all the birds use their feathers to control and distribute their power along the flying time, a solution might be design of a piezoelectric plate as feathers, which scavenges energy directly from the fluid flow. Cantilevered beam with piezo-ceramic layer undergoing vortex-induced vibrations can convert the mechanical energy available from the ambient environment to a usable electrical power. Since a flow-driven piezoelectric composite beam takes a form of natural three-way coupling of the turbulent fluid...