Eindimensionale Berechnung instationärer und diskontinuierlicher Strömungen in abflussschwachen naturnahen Fließgewässern

Almost all major hydraulic engineering activities involve the computation of water levels and discharges along a river reach. Computation of the water level is essential for the determination of the effect of a hydraulic structure on the water level, inundation of land due to dams, weirs or barrage constructions and determination of flooded areas. Because of its practical importance, the computation has been a topic of continued interest to hydraulic engineers. Today complex hydraulic phenomena occurring in rivers can be simulated with both two- and three dimensional numerical models. So far, these models can not be easily used in engineering practice due to high computational costs. On the other hand, one dimensional models offer the possibility of cheap evaluating the response of the hydraulic system to a variety of practical situations. The one-dimensional models developed so far are mostly applied to rivers which are characterized by large discharges and homogeneous and compact geometries with the flow being only subcritical. On the contrary, small natural rivers are characterized by a highly irregular cross section configuration with abrupt contractions and expansions in channel width, varying boundary roughness along the wetted perimeter and the flow changing from sub- to supercritical and vice versa. When applying one of the existing one-dimensional models to one of these small rivers, spatial oscillations are often observed in the computed water level and discharge. This work deals with the use of high-resolution shock-capturing schemes to solve steady and unsteady one-dimensional flows with steep waves in rivers. The Godunov first order upwind scheme is utilized to compute flows with bottom slope and friction terms. Additionally, a high-resolution TVD scheme (WAF) with second-order accuracy is incorporated into the model. To minimize the error due to an inflexible numerical grid applied to the numerical simulation of the flow phenomena, it is desirable to use mesh refinement to cluster grid points in regions where they are most needed, e.g. around shocks or in other regions where the solution has steep gradient. For time-dependent problems the region of refinement must move adaptively with the zone of interest. Therefore an effective adaptive mesh refinement strategy with refinement in both space and time has been added to the hydraulic model. Numerical results are obtained from the proposed model for a series of one-dimensional test cases and are compared with analytical solutions and experimental measurements where available. It is shown that the model is accurate and highly stable in accommodating strong gradients and discontinuities in such transcritical flows, and therefore it may be considered a reliable numerical model for practical hydraulic engineering applications.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Schramm, Jens Michael

Contributors dc:contributor

• Köngeter, Jürgen

• info:eu-repo/classification/ddc/620
• Fließgewässer
• Naturnahes Gewässer
• Instationäre Strömung
• Diskontinuierlicher Vorgang
• Numerisches Modell
• Ingenieurwissenschaften
• diskontinuierliche Strömung
• Fließwechsel
• Godunov verfahren
• adaptive Netzverfeinerung
• Saint-Venant Gleichung
• TVD Verfahren

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123600%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61999