River dunes are submerged bed forms on the bottom of alluvial channels. They develop due to the complex interaction of water flow and sediment. River dunes influence the water level, by creating further bed roughness because of form drag and can form a threat to shipping activities. For that reason they deserve the attention of river basin managers. The importance of physical modelling in contrast to the use of equilibrium predictors or empirical models lies in the applicability in extreme events. Equilibrium predictors don’t consider the time component of dune development. Hysteresis for dune height is observed to be strong during a flood wave, that makes the use of equilibrium predictors inaccurate. Empirical modelling is dependent upon calibration with data. The availability of data for extreme events is restricted or absent, so the necessity for physical modelling is strong. The Dune Development (DuDe) model is created to describe river dune evolution by combining two-dimensional vertical (2DV) flow equations with a sediment transport formula using a parameterization of flow separation to avoid complex turbulence modeling inside the flow separation zone. Dune growth, migration and merging of river dunes is described well by the DuDe model.
Contents 1
INTRODUCTION
1.1 RIVER DUNE MODELLING
1.2 METHODOLOGY & REPORT OUTLINE
2 RESEARCH BACKGROUND
2.1 RELEVANCE OF PHYSICAL MODELLING
2.2 PROCESSES IN RIVER DUNE DEVELOPMENT
2.3 MODELLING OF RIVER DUNES
2.4 DUDE MODEL
2.5 MODEL SIMULATIONS
3 FLUME EXPERIMENTS
3.1 METHOD AND EXPERIMENTAL SET-UP
3.2 RESULTS
3.3 POSSIBLE DUNE SPLITTING MECHANISMS
4 IMPLEMENTING DUNE SPLITTING
4.1 MODEL BEHAVIOUR
4.2 RANDOM DISTURBANCE
4.3 STABILIZING EFFECT OF SLOPE TERMS
4.4 SUPERPOSED WAVELETS
4.5 CONTINUOUS APPLICATION OF DUNE SPLITTING.
4.6 RESULTS OF THE IMPLEMENTATION OF DUNE SPLITTING
4.7 EVALUATION OF EQUILIBRIUM CHARACTERISTICS
5 SENSITIVITY ANALYSIS
5.1 SENSITIVITY ANALYSIS OF THE SEDIMENT TRANSPORT FORMULA
5.2 SENSITIVITY ANALYSIS FOR THE WAVELET PARAMETERS HWAVE AND LCRIT
6 DISCUSSION
6.1 EXPERIMENTS
6.2 BEDFORMER
6.3 CRITICAL STOSS SIDE LENGTH (LCRIT)
6.4 THE EXISTENCE OF A DYNAMIC EQUILIBRIUM
7 CONCLUSION & RECOMMENDATIONS
7.1 CONCLUSIONS
7.2 RECOMMENDATIONS
REFERENCES
APPENDICES…
Source: University of Twente
Download URL 2: Visit Now