2001 Fiscal Year Final Research Report Summary
Construction of Flood Flows Simulation Model Based on High Resolution Upwinding Finite Difference Method
| Project/Area Number |
11450190
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
AKIYAMA Junichiro Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (20192916)
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| Co-Investigator(Kenkyū-buntansha) |
JHA Akithilesh Kumar Kyushu Institute of Technology, Faculty of Engineering, Research Associate, 工学部, 助手 (00304858)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Flood Flow Simulation / Flux-Difference Splitting / Finite-Volume Method / Unstructured Grid System / Dam Break Flow / Hydrodynamic Force / Laboratory Experiment / PTV |
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| Research Abstract |
A first-order accurate numerical model- based on Flux-Difference Splitting (FDS) technique and unstructured Finite-Volume Method(FVM) for 2D Flood Flows (FUF-2DF Model) is newly constructed. The model uses unstructured triangular grid system and Incorporates conservative properties as well as signal propagation through FDS technique. A SA- FUF-2DF Model, which is essentially a spatially averaged FUF-2DF Model, is also developed. The FUF-2DF Model is designed to be appled to such larger elements existing In a flood plain than a grid size as buildings and others, while the GA-FUF-2DF Model is designed to treat such smaller elements than a grid size as trees, small houses and others existing within a grid. In the GA-FUF-2DF Model , the forces acting from elements on a flow are evaluated as reaction forces.
For comprehensive verification of the model, experiments on two-dimensional dam-break flood waves propagating in a channel as well as a floodplain in presence of submerged and/or unsubme
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rged larage structures and/or small elements are conducted. A new methods to obtain the depths and the surface velocities of flood flows propagating on a flood plain In dry-bed condition have been developed: the depths and the surface velocities of flood flows are measured by using the Image analysis by a computer and Particle Tracking Velocimetry(PTV), respectively. The model verifications against these experimental data show that the proposed model can reproduce flood flows with structures with reasonable accuracy.
A new numerical model for free-surface flow simulations Is constructed; first and second-order flux-difference splitting schemes are combined with the Preissmann slot to simulate flows in a closed conduit, wherein the flow may change from free-surface to pressurized flow and vice versa. The models can simulate conduits with uniform cross-sections of arbitrary shape as well as with bed slope and bed friction. The models are verified with available experimental data on free-surface-pressurized flows for pipes and rectangular conduits. Thereafter, the models are tested against some exacting sample problems. It Is demonstrated that the models yield very reasonable results In all the cases considered. A sensitivity analysis Is performed for the size of the slot and useful conclusions are drawn from the study for the simulation of free-surface pressurized flows.
Hydrodynamic force exerting on a squre pillar placed In steady or unsteady free surface shear flows were Investigated experimentally. In steady flows, It is found that the drag coefficients of a squre pillar at a given 'a decreases with B/d in the range of B/d=3〜14 and is constant when B/d≧14, and that the values of Cd in a shear flow are different from those in uniform flow. Diagrams to describe the relationships between Cd and α as well as Cd and B/d are presented. In unsteady flows, It Is found that the ratio of surface to depth-averaged velocity is about 1.12. The magnitude of Cd of the pillar 1D dam break flows Is compared with that of steady uniform flows, and increases very slowly with t* after t*>70. Less
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