In this study, a comprehensive approach including mathematical, numerical and experimental study has been taken in order to develop new models for describing free surface flow behavior in porous media. The study suggested that modeling free-surface flow in porous media is possible using a single equation capable of showing proper transition between inertial and classical Darcian flow, based on the similarity distribution functions of depth and velocity. The developed integral model inherits both the flow regimes as depicted in the analysis. For both laminar and turbulent flows through porous media, the integral models give satisfactory results. Also the proposed algorithm for numerical simulation is capable of solving various problems of free-surface flow through porous media. This study adds a new dimension to fluid flow in porous media by replacing Darcy's equation with new models that are capable of representing both Darcy and non-Darcy flow behaviors. These are new nonlinear ordinary differential equations inherited both the flow regimes investigated. Integral formulations for unsteady depth distribution, velocity and front speed under constant water level and constant flux discharge inlet conditions have been developed based on similarity law. The formulations presented provide additional analytical insight about the intrusion dynamics. It is pointed out that, based on the self-similarity analysis, the temporal intrusion processes can be categorized into the inertia-pressure (IP) and the pressure-drag (PD) regimes. The early inertia-pressure regime is followed by the pressure-drag regime. In addition, the integral models proposed can be successfully used for the solution of a host of other nonlinear problems that admit self-similarity. The analytical and numerical solutions for constant inlet water level condition are verified with experimental observations. The unsteady distributions of flow depth, inflow velocity and front speeds are compared for various porous media characterized by its corresponding porosity and permeability. Analyses indicate that the integral models clearly represent the nonlinear flow behavior in porous media both in laminar and turbulent flow conditions. The integral model results are in agreement with those obtained by similarity solution for the temporal change of velocity, depth at inlet and front positions. The thesis also presents a computational fluid dynamics (CFD) model developed for the analysis of unsteady free-surface flows through porous media. Vertical two-dimensional numerical simulations are carried out for the free-surface flow inside the porous media governed by a set of Navier-Stokes equations extended for porous media flow. This model includes the convective and local inertia terms along with viscous diffusion term and resistance term comprising Darcy's linear resistance and Forchheimer's inertial resistance terms. The Finite volume method is applied using constrained interpolated propagation (CIP) method and highly simplified marker and cell (HSMAC) type pressure solver for the numerical solution. The evolution of moving free surface is governed by volume of fluid (VOF) method, adapted for the flow through porous media. To prevent the spurious oscillation and generate diffusion-free sharp interface, a third order monotone upstream-centered schemes for conservation laws (MUSCL) type total variation diminishing (TVD) schemes is used to solve the VOF convection equation. The power law derivation and validation for the general flux inflow condition are made for a channel having a backward facing step. The result of theoretical analysis is compared with that of the numerical simulation and it shows a good agreement. The model can be a tool for the proposition of some empirical flow relationships using multivariate correlation. In the case of rapid vertical infiltration of water through a vertical column filled with porous media, a number of experiments and analytical investigations are carried out to see the effect of acceleration in the intrusion process. It is concluded that the conventional infiltration models like Green-Ampts infiltration model cannot account for the acceleration effect in the case of high velocity flow. It is revealed that it takes certain time for intruding water to be accelerated to its peak velocity before decreasing to almost constant velocity. The investigations are made for two different cases: constant water level and variable water level above the porous media. For porous media having low permeability, the effect of acceleration was not so significant. In the case of dam break flow over horizontal porous strata, the model is applied to a complicated domain regarding both geometry and flow boundary conditions. Single set of governing equation is implemented to simulate the complex phenomenon. The model shows its capability in simulating the flow where interface between pressurized and open channel flow moves forward. The vertical acceleration has a significant effect on the rapid vertical infiltration which the shallow water equations cannot account for. In particular, it is shown that vertical two dimensional numerical solution that couples the fluid and solid systems simultaneously at macroscopic scale are feasible and extremely beneficial, shedding a new light into the phenomena unavailable otherwise. It is also found that the proposed numerical model can be used for the determination of storm water storage in porous sub-base in a typical road section. The capability of the model is assessed by using the unsteady inflow condition so as to simulate the condition during high precipitation. The model could be a promising tool for planners and decision makers for effective drainage calculations to mitigate urban flood. The model successfully simulates the free surface flow in the bulk fluid as well as in the porous region. The velocities and stresses are assumed to be continuous at the interface of free and porous media so that a single set of governing equations could be solved. The robustness of the model is demonstrated by the capability of the numerical approach proposed in this thesis. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14916号 / 工博第3143号 / 新制||工||1471(附属図書館) / 27354 / UT51-2009-M830 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 細田 尚, 教授 戸田 圭一, 准教授 岸田 潔 / 学位規則第4条第1項該当
| Identifer | oai:union.ndltd.org:kyoto-u.ac.jp/oai:repository.kulib.kyoto-u.ac.jp:2433/85382 |
| Date | 24 September 2009 |
| Creators | GHIMIRE, BIDUR |
| Contributors | 細田, 尚, 戸田, 圭一, 岸田, 潔, ギミレ, ビドゥール |
| Publisher | 京都大学 (Kyoto University), 京都大学 |
| Source Sets | Kyoto University |
| Language | English |
| Detected Language | English |
| Type | DFAM, Thesis or Dissertation |
| Format | application/pdf |
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