Browsing by Subject "Two-phase flow"
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Item Computational two-phase flows in conduits with and without heat addition(Texas Tech University, 1992-05) Luthan, Jurizal JulianThe main objectives of this study of two-phase ga^-liquid flows are to reduce the time and cost and to improve prediction capability of process development in comparison with purely empirical design methods. The problem associated with mathematical modeling of the detailed flow patterns in two-phase flows involves the solution of strongly coupled, nonlinear partial differential equations of the field equations. The solution of these equations lies well beyond any existing analytical approach. Therefore finite-diflference approximations, based on IPSA (Inter-P,hase £lip A^ialyzer) algorithm, are used to solve the problem. Three cases are considered in this study. The first is the problem of two-phase gas-liquid stratified flow with constant properties for both fluids. The second is the problem of idealized boiling problem where, again, the properties of the two fluids are taken to be constant. As the last one, the previous problem is revisited by relaxing the simplifying assumptions. The last two cases are treated as pseudo-transient problems. In addition, all three problems are computed with one spatial dimension dependency. While the flow model employed is two-fluid or six-equation model. The results are then compared with the available analytical solution and experimental data. It was found that they are satisfactorily comparable. The methodology developed may be useful in future research with other fluid pairs or components.Item Developing two-phase flow with periodic longitudinal heat flux asymmetry(Texas Tech University, 1979-08) Lee, Yung FengNot availableItem Development of a coupled wellbore-reservoir compositional simulator for horizontal wells(2010-12) Shirdel, Mahdy; Sepehrnoori, Kamy, 1951-; Ribeiro, Paulo R.Two-phase flow occurs during the production of oil and gas in the wellbores. Modeling this phenomenon is important for monitoring well productivity and designing surface facilities. Since the transient time period in the wellbore is usually shorter than reservoir time steps, stabilized flow is assumed in the wellbore. As such, semi-steady state models are used for modeling wellbore flow dynamics. However, in the case that flow variations happen in a short period of time (i.e., a gas kick during drilling) the use of a transient two-phase model is crucial. Over the last few years, a number of numerical and analytical wellbore simulators have been developed to mimic wellbore-reservoir interaction. However, some issues still remain a concern in these studies. The main issues surrounding a comprehensive wellbore model consist of fluid property calculations, such as black-oil or compositional models, governing equations, such as mechanistic or correlation-based models, effect of temperature variation and non-isothermal assumption, and methods for coupling the wellbore to the reservoir. In most cases, only standalone wellbore models for blackoil have been used to simulate reservoir and wellbore dynamic interactions. Those models are based on simplified assumptions that lead to an unrealistic estimation of pressure and temperature distributions inside the well. In addition, most reservoir simulators use rough estimates for the perforation pressure as a coupling condition between the wellbore and the reservoir, neglecting pressure drops in the horizontal section. In this study, we present an implementation of a compositional, pseudo steady-state, non-isothermal, coupled wellbore-reservoir simulator for fluid flow in wellbores with a vertical section and a horizontal section embedded on the producing reservoir. In addition, we present the implementation of a pseudo-compositional, fully implicit, transient two-fluid model for two-phase flow in wellbores. In this model, we solve gas/liquid mass balance, gas/liquid momentum balance, and two-phase energy equations in order to obtain the five primary variables: liquid velocity, gas velocity, pressure, holdup and temperature. In our simulation, we compared stratified, bubbly, intermittent flow effects on pressure and temperature distributions in either a transient or steady-state condition. We found that flow geometry variation in different regimes can significantly affect the flow parameters. We also observed that there are significant differences in flow rate prediction between a coupled wellbore-reservoir simulator and a stand-alone reservoir simulator, at the early stages of production. The outcome of this research leads to a more accurate and reliable simulation of multiphase flow in the wellbore, which can be applied to surface facility design, well performance optimization, and wellbore damage estimation.Item Discontinuous Galerkin finite element methods applied to two-phase, air-water flow problems(2005) Eslinger, Owen John; Wheeler, Mary F. (Mary Fanett)A set of discontinuous Galerkin (DG) finite element methods are proposed to solve the air-water, two-phase equations arising in shallow subsurface flow problems. The different time-splitting approaches detailed incorporate primal formulations, such as Oden-Baumann-Babuska DG (OBB-DG), Symmetric Interior Penalty Galerkin (SIPG), Non-Symmetric Interior Penalty Galerkin (NIPG), and Incomplete Interior Penalty Galerkin (IIPG); as well as a local discontinuous Galerkin (LDG) method applied to the saturation equation. The two-phase flow equations presented are split into sequential and implicit pressure/explicit saturation (IMPES) formulations. The IMPES formulation introduced in this work uses one of the primal DG formulations to solve the pressure equation implicitly at every time step, and then uses an explicit LDG scheme for saturation equation. This LDG scheme advances in time via explicit Runge-Kutta time stepping, while employing a Kirchoff transformation for the local solution of the degenerate diffusion term. As fluid saturations may be discontinuous at the interface between two material types, DG methods are a natural fit for this problem. An algorithm is introduced to efficiently solve the system of equations arising from the primal DG discretization of the model Poisson’s Equation on conforming grids. The eigenstructure of the resulting stiffness matrix is examined and the reliance of this system on the penalty parameter is detailed. This analysis leads to an algorithm that is computationally optimal and guaranteed to converge for the order of approximation p = 1. The algorithm converges independently of h and of the penalty parameter σ. Computational experiments show that this algorithm also provides an excellent preconditioning step for higher orders of approximation and extensions are given to 2D and 3D problems. Computational results are also shown for a more general second order elliptic equation, for example, cases with heterogeneous and non-isotropic K. The numerical schemes presented are verified on a collection of standard benchmark problems and the two-phase flow formulations are validated using empirical results from the groundwater literature. These results include bounded column infiltration problems in which the soil air becomes compressed and entrapped, as well as other shallow subsurface infiltration problems. It is shown that the IMPES approach introduced holds promise for the future, especially for problems with very small, or even zero, capillary pressure. Such problems are commonly found in the SPE literature. Finally, initial computational results are shown which relate to a simplified model of the CO2 sequestration problem.Item Effect of liquid composition on two-phase, cocurrent down flow packed beds(Texas Tech University, 1982-05) Han, Boo-hakNot availableItem Flow patterns and instabilities in two-phase down flow in packed beds(Texas Tech University, 1978-12) Halfacre, GlennNot availableItem Forced convection heat transfer to a single and two-phase steam/water mixture in a helical coil with radiant heating(Texas Tech University, 1981-12) Vafaie, Foad NThe purpose of this study has been to perform an analytical and experimental investigation into the heat transfer characteristics for a once-through steam generator with a helical flow geometry. The application is the receiver for a fixed hemispherical mirror solar concentrator on the Crosbyton Solar Power Project. In this design, the working fluid, water, goes successively through the single-phase liquid, two-phase and super-heated vapor regimes in a once-through, helically wrapped tube bundle subjected to nonuniform, asymmetrical radiant heating. Individual segments of the radiation profile for the receiver were simulated using high intensity, line source quartz lamps providing concentrations of up to 240 suns. A segment of the helical coil was instrumented and mounted in the radiation field. Test section instrumentation included inlet fluid flow rate, inlet and exit fluid pressure and temperature, and 42 type K thermocouples welded to the surface of the coil. The incident radiation field was mapped using a Gordon type heat flux transducer calibrated for the quartz lamp spectrum. An upstream hot oil heat exchanger provided inlet fluid conditions to the test section consistent with the segment of the receiver being simulated e.g., single-phase or two-phase. The range of test conditions included an incident radiation flux of 6,000 to 27,000 Btu/hr-ft , a flow rate of 100 to 500 Ibm/hr, an inlet pressure of 100 to 500 psia, and an inlet quality of 0 to 70 percent. A numerical analysis was developed to predict the local internal heat transfer coefficients and fluid state based on the measurements obtained in the test procedure discussed above. The analysis included consideration of the externally applied radiation field, convective and radiative heat losses, two-dimensional conduction through the tube wall, and.convection to the internal fluid. The results show that there is a significant change in the angtilar variation of the internal heat transfer coefficient at low quality when compared with values for high quality. At low quality, the highest internal heat transfer coefficients are obtained on the tube surface farthest from the axis of the coil. At high qualities, this changes to yield the highest coefficients on the tube surface closest to the coil axis. Factors contributing to this phenomena include radial acceleration, induced secondary flow, flow acceleration along the flow axis, and the onset of film boiling. The integrated average values of the heat transfer coefficient for the subcooled liquid and two-phase were correlated against dimensionless parameters of the flow such as the Reynolds number, Prandtl number, boiling number and tube-to-coil diameter ratio.Item Heat transfer in two phase flows in packed beds(Texas Tech University, 1984-08) Wang, Yu FengNot availableItem Mathematical modeling of heat transfer in packed beds with two phase flow(Texas Tech University, 1981-08) Tailor, Shailesh MNot availableItem Mimetic finite differences for porous media applications(2014-05) Al-Hinai, Omar A.; Wheeler, Mary F. (Mary Fanett)We connect the Mimetic Finite Difference method (MFD) with the finite-volume two-point flux scheme (TPFA) for Voronoi meshes. The main effect is reducing the saddle-point system to a much smaller symmetric-positive definite matrix. In addition, the generalization allows MFD to seamlessly integrate with existing porous media modeling technology. The generalization also imparts the monotonicity property of the TPFA method on MFD. The connection is achieved by altering the consistency condition of the velocity bilinear operator. First-order convergence theory is presented as well as numerical results that support the claims. We demonstrate a methodology for using MFD in modeling fluid flow in fractures coupled with a reservoir. The method can be used for nonplanar fractures. We use the method to demonstrate the effects of fracture curvature on single-phase and multi-phase flows. Standard benchmarks are used to demonstrate the accuracy of the method. The approach is coupled with existing reservoir simulation technology.Item A multigrid preconditioner for two-phase flow in porous media(2001-12) Eaton, Frank Joseph; Wheeler, Mary F. (Mary Fanett)Item Saturation profiles from petroleum reservoir simulation studies compared with Buckley-Leverett results(Texas Tech University, 1986-05) Luo, WeizhongThe objective of the research program reported herein is to develop and describe methods for reservoir simulation, including computer programs, in order to analyze two-phase fluid flow in a one-dimensional reservoir system. Moreover, several tests will be presented in order to verify the validity of the model.Item Simulation of rocket plume impingement and dust dispersal on the lunar surface(2012-12) Morris, Aaron Benjamin; Varghese, Philip L.; Goldstein, David Benjamin, doctor of aeronautics; Metzger, Philip; Trafton, Laurence M.; Raman, VenkatramananWhen a lander approaches a dusty surface, the plume from the descent engine impinges on the ground and entrains loose regolith into a high velocity spray. This problem exhibits a wide variety of complex phenomena such as highly under-expanded plume impingement, transition from continuum to free molecular flow, erosion, coupled gas-dust motions, and granular collisions for a polydisperse distribution of aerosolized particles. The focus of this work is to identify and model the important physical phenomena and to characterize the dust motion that would result during typical lunar landings. A hybrid continuum-kinetic solver is used, but most of the complex physics are simulated using the direct simulation Monte Carlo method. A descent engine of comparable size and thrust to the Lunar Module Descent Engine is simulated because it allows for direct comparison to Apollo observations. Steady axisymmetric impingement was first studied for different thrust engines and different hovering altitudes. The erosion profiles are obtained from empirically derived scaling relationships and calibrated to closely match the net erosion observed during the Apollo missions. Once entrained, the dust motion is strongly influenced by particle-particle collisions and the collision elasticity. The effects of two-way coupling between the dust and gas motions are also studied. Small particles less than 1 µm in diameter are accelerated to speeds that exceed 1000 m/s. The larger particles have more inertia and are accelerated to slower speeds, approximately 350 m/s for 11 µm grains, but all particle sizes tend obtain their maximum speed within approximately 40 m from the lander. The maximum particle speeds and erosion rates tend to increase as the lander approaches the lunar surface. The erosion rates scale linearly with engine thrust and the maximum particle speed increases for higher thrust engines. Dust particles are able to travel very far from the lander because there is no background atmosphere on the moon to inhibit their motion. The far field deposition is obtained by using a staged calculation, where the first stages are in the near field where the flow is quasi-steady and the outer stages are unsteady. A realistic landing trajectory is approximated by a set of discrete hovering altitudes which range from 20 m to 3 m. Larger particles are accelerated to slower speeds and are deposited closer to the lander than smaller particles. Many of the gas molecules exceed lunar escape speed, but some gas molecules become trapped within the dust cloud and remain on the moon. The high velocity particulate sprays can be damaging to nearby structures, such as a lunar outpost. One way of mitigating this damage is to use a berm or fence to shield nearby structures from the dust spray. This work attempts to predict the effectiveness of such a fence. The effects of fence height, placement, and angle as well as the model sensitivity to the fence restitution coefficient are discussed. The expected forces exerted on fences placed at various locations are computed. The pressure forces were found to be relatively small at fences placed at practical distances from the landing site. The trajectories of particles that narrowly avoid the fence were not significantly altered by the fence, suggesting that the dust motion is weakly coupled to the gas in the near vicinity of the fence. Future landers may use multi-engine configurations that can form 3-dimensional gas and dust flows. There are multiple plume-plume and plume-surface interactions that affect the erosion rates and directionality of the dust sprays. A 4-engine configuration is simulated in this work for different hovering altitudes. The focusing of dust along certain trajectories depends on the lander hovering altitude, where at lower altitudes the dust particles focus along symmetry planes while at higher altitudes the sprays are more uniform. The surface erosion and trenching behavior for a 4-engine lander are also discussed.