1996 Fiscal Year Final Research Report Summary
STUDY ON UNSTEADY RESPONSE CHARACTERISTICS OF FLOW AROUND HYDRAULIC STRUCTURES ENVIRONMENTALLY CONSIDERED
| Project/Area Number |
07650597
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
水工水理学
|
|---|
| Research Institution | Nagoya Institute of Technology |
|---|
Principal Investigator |
TOMINAGA Akihiro Nagoya Institute of Technology, 工学部, 助教授 (60135530)
|
|---|
| Project Period (FY) |
1995 – 1996
|
| Keywords | unsteady flow / compound channel / vegetated flow / 2-d numerical calculation / large scale vortex / spur dike / flood routing / hydraulic structure |
|---|
| Research Abstract |
The purpose of this study is to clarify the response characteristics of the flow around the vegetation on the flood plains under changing discharge and to investigate the middle-scale unsteady flow structures around the vegetation and the spur dikes. The study on vegetated two-stage flow was conducted experimentally by using unsteady water supply system and numerically by using 2-D depth averaged mathematical model. Next, unsteady turbulent flow structures around the spur dikes and vegetated zone were investigated.
Some noticeable differences between unsteady flow structures with and without vegetation were revealed. The vegetation in the flood plains increases the unsteadiness of the main-channel velocity by the effects of vegetation arrangement. The shortly vegetated zone in the flood plains causes a sharp decrease of the flow depth in front of that and increases an upstream stage extremely. 2-D depth-averaged numerical calculation technique for unsteady flow with vegetation in flood
… More
plains was developed. The calculated results reproduce well the characteristic tendency of the experiments. This calculation method is useful for the flood routing passing such a complex flow field.
The nature of flow and vortex structure around the spur dikes with various permeability were investigated. When spur dike is non-permeable, a strong circulation is generated behind the spur dike, but it diminishes in the movable-bed condition, because of massive scour and deposition. The permeable spur dike with refracted flow has mild effects for resistance and scouring but can make broad circulation zone behind it. The flow and vortex structures are studied experimentally in compound open channel flows with loosely and densely wooded zone on flood plains. The large-scale periodic vortex motion was observed in these vegetated flows and it could be regenerated by using the unsteady depth-averaged 2-D simulation.
We believe that the results of this study give useful knowledge for hydraulic engineering. Less
|
