The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Narendra Kumar - One of the best experts on this subject based on the ideXlab platform.
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Random-Phase Reservoir and a quantum resistor : The Lloyd model
Physical Review B, 2007Co-Authors: Dibyendu Roy, Narendra KumarAbstract:We introduce Phase disorder in a 1D quantum resistor through the formal device of `fake channels' distributed uniformly over its length such that the out-coupled wave amplitude is re-injected back into the system, but with a Phase which is random. The associated scattering problem is treated via invariant imbedding in the continuum limit, and the resulting transport equation is found to correspond exactly to the Lloyd model. The latter has been a subject of much interest in recent years. This conversion of the random Phase into the random Cauchy potential is a notable feature of our work. It is further argued that our Phase-randomizing Reservoir, as distinct from the well known Phase-breaking Reservoirs, induces no decoherence, but essentially destroys all interference effects other than the coherent back scattering.
Dibyendu Roy - One of the best experts on this subject based on the ideXlab platform.
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Random-Phase Reservoir and a quantum resistor : The Lloyd model
Physical Review B, 2007Co-Authors: Dibyendu Roy, Narendra KumarAbstract:We introduce Phase disorder in a 1D quantum resistor through the formal device of `fake channels' distributed uniformly over its length such that the out-coupled wave amplitude is re-injected back into the system, but with a Phase which is random. The associated scattering problem is treated via invariant imbedding in the continuum limit, and the resulting transport equation is found to correspond exactly to the Lloyd model. The latter has been a subject of much interest in recent years. This conversion of the random Phase into the random Cauchy potential is a notable feature of our work. It is further argued that our Phase-randomizing Reservoir, as distinct from the well known Phase-breaking Reservoirs, induces no decoherence, but essentially destroys all interference effects other than the coherent back scattering.
Naoto Takeno - One of the best experts on this subject based on the ideXlab platform.
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Thermal and geochemical structure of the Uenotai geothermal system, Japan
Geothermics, 2000Co-Authors: Naoto TakenoAbstract:The Uenotai geothermal area is located in southern Akita prefecture of northern Honshu Island. The Uenotai geothermal system is a liquid-dominated system with a central zone of aquifer boiling. The two-Phase Reservoir has evolved from liquid in the natural state due to exploitation. Gas composition of the vapor Phase in the Reservoir is nearly in equilibrium and correlates with the vapor fraction in the Reservoir and with discharging steam quality. The marginal part of the Uenotai system has cooled with the drop in ground-water level. The chemical characteristics of the geothermal water indicate mixing of the immature high Cl source water with conductively heated or steam-heated shallow water or surface water, as well as boiling and steam gain.
Mitsuo Matsumoto - One of the best experts on this subject based on the ideXlab platform.
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A single-Phase Reservoir simulation method based on a roughly distributed and highly permeable fracture network model with applications to production and reinjection problems
Geothermics, 2020Co-Authors: Mitsuo MatsumotoAbstract:Abstract A single-Phase Reservoir simulation method has been developed based on a roughly distributed and highly permeable fracture network model to address production and reinjection problems. This method provides effective estimates of Reservoir productivity during active explorational and developmental projects. Comparisons with analytical solutions and a representative Reservoir simulator support the method’s validity, and behavior of original features generated from the numerical solutions is investigated. Such model features include changes in pressure and tracer mass fraction in a highly heterogeneous pore distribution, as well as thermal decay of thermo-sensitive tracers.
Urmila Ghia - One of the best experts on this subject based on the ideXlab platform.
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Comparison of pore-scale capillary pressure to macroscale capillary pressure using direct numerical simulations of drainage under dynamic and quasi-static conditions
Advances in Water Resources, 2021Co-Authors: Santosh Konangi, Nikhil K. Palakurthi, N. K. Karadimitriou, Ken Comer, Urmila GhiaAbstract:Abstract Conventional macroscale two-Phase flow equations for porous media (such as Darcy's law and Richards Equation) require a constitutive relation for capillary pressure (Pc). The capillary pressure relation significantly impacts the behavior and prediction of fluid flow in porous media, and needs to accurately characterize the capillary forces. In a typical laboratory experiment, a functional macroscopic capillary pressure-saturation (Pc-Sw) relationship is measured as the difference between the pressures of the non-wetting-Phase Reservoir at the inlet (Pnw) and wetting-Phase Reservoir at the outlet (Pw) of a porous medium. It is well-known that this traditional macroscopic capillary pressure definition is valid only at equilibrium conditions and if the Phases are connected. Under non-equilibrium (dynamic) conditions, when the fluids are moving, the macroscopic capillary pressure measured in experiments implicitly includes the pressure head caused by viscous effects. The goal of the present effort is to understand how well the traditional macroscopic capillary pressure definition represents the pore-scale capillary forces under different flow conditions. Using direct numerical simulations (DNS) of two-Phase flow in a porous medium, we evaluate the capillary pressure at the pore-scale, and compare it to the macroscopic capillary pressure, Pc(Sw), that is typically measured in experiments using pressure transducers. The pore-scale capillary pressure is the pressure difference across the interface between two fluids as the fluids move through a porous medium; the interface pressure differences at fluid-fluid invasion front are averaged across all the pores of the porous medium to yield a representative pore-scale capillary pressure curve, referred to as the interface capillary pressure. The pore-scale interface capillary pressure represents the “true” capillary forces in the system, since depends only on the pore morphology (shape) and interfacial energy of the two fluids, and does not account for the viscous dissipation. In experiments it is difficult to measure the interface capillary pressure jump without accounting for the viscous pressure head, which is at least an order of magnitude larger. Upscaling the pore-scale capillary pressure is an essential step for complete characterization of capillary-dominant two-Phase flow in a porous medium at the laboratory scale. Drainage is simulated under equilibrium (quasi-static) and non-equilibrium (dynamic) conditions for various capillary numbers. The Navier–Stokes (NS) equations are solved in the pore space using the open-source finite-volume computational fluid dynamics (CFD) code, OpenFOAM. The Volume-of-Fluid (VOF) method is employed to track the evolution of the fluid–fluid interfaces, and a contact angle is used to account for the effect of wall adhesion. The simulations are first validated with published experimental data for dynamic and quasi-static drainage in a micromodel. From the microscale simulations, the interface capillary pressure is determined, and compared to the macroscopic capillary pressure under equilibrium and non-equilibrium conditions. Our results show the traditionally-measured macroscopic capillary pressure curves exhibit a strong dependence on the capillary number under dynamic flow conditions. In contrast, the interface capillary pressure-saturation relation, which relies on pore-scale pressure differences at the invasion front, is almost invariant of flow conditions (dynamic and quasi-static).